🏷

Classifications

Harrison's Part

◆

Subtypes

3

Left-sided native valve endocarditis

The commonest form, affecting mitral and aortic valves on a previously abnormal or normal valve. It carries the embolic stroke risk, because vegetation fragments enter the systemic circulation, and it is the population in which oral step-down therapy was tested.

Right-sided endocarditis, typically tricuspid

Strongly associated with injection drug use, and mechanistically distinct in a way the entry's own prose already argued. It commonly occurs on a structurally normal valve, embolises to the lungs rather than the brain, and generally carries a better prognosis with medical therapy alone. Modelling it as a subtype rather than a variant reflects that the differences are in substrate, embolic destination, and outcome together.

Prosthetic valve endocarditis

Infection on implanted material, where biofilm on a foreign surface makes medical cure less likely and perivalvular extension more common. Prosthetic involvement is an independent predictor of in-hospital death.

Show evidence (1 reference)

PMID:19273776 SUPPORT Human Clinical

"Prosthetic valve involvement (odds ratio, 1.47; 95% confidence interval, 1.13-1.90)"

Quantifies prosthetic involvement as an independent predictor of in-hospital mortality with a confidence interval.

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Discussions and Knowledge Gaps

2

Should antibiotic prophylaxis be given before dental procedures, when the mechanism is plausible but the evidence does not support it and a definitive trial is impractical?

CONTROVERSY OPEN prophylaxis_mechanism_evidence_gap

Attached to

pathophysiology#Transient bacteraemia treatments#Antibiotic prophylaxis before dental procedures

The mechanistic argument is straightforward. Dental procedures cause bacteraemia, bacteraemia seeds a receptive endocardial surface, so suppressing the bacteraemia should prevent the disease. Practice guidelines have progressively narrowed the indication anyway, because the evidence never supported the inference. A systematic review found the evidence base limited and heterogeneous and, more damagingly, concluded that post-procedural bacteraemia is not a good surrogate for the disease, which removes the empirical link the mechanistic argument depends on. The plausible explanation is that cumulative everyday bacteraemia from chewing and tooth brushing dwarfs the procedural contribution, in which case prophylaxis targets a negligible fraction of exposure. This entry curates the practice with its own contradicting evidence attached rather than omitting it, because omission would leave the mechanistic argument looking unopposed. The question is unlikely to be settled, since the authors themselves note that a randomised trial is logistically impractical for so rare an outcome.

Proposed experiments

Large linked-records case-control study of dental procedures and subsequent infective endocarditis

exp_ie_prophylaxis_case_control

Use linked dental and hospital records at national scale to compare recent invasive dental procedure exposure between incident cases and matched controls, stratified by cardiac risk category and prophylaxis receipt. The decision criterion is whether procedure exposure is associated with disease at all. If it is not, the mechanistic rationale for prophylaxis fails at its first step, and no trial is needed.

Show evidence (2 references)

PMID:28213367 SUPPORT Human Clinical

"The evidence base for the use of AP is limited, heterogeneous and the methodological quality of many studies is poor. Postprocedural bacteraemia is not a good surrogate endpoint for IE."

Establishes both that the direct evidence is inadequate and that the surrogate endpoint underpinning the mechanistic case is invalid.

PMID:28213367 SUPPORT Human Clinical

"Given the logistical challenges of a randomised trial, high-quality case-control studies would help to evaluate the role of dental procedures in causing IE and the efficacy of AP in its prevention."

PARTIAL. States why the question is likely to remain open and what design could still address it, which is what makes this a standing controversy rather than a resolved negative.

Is a pre-existing sterile thrombus a strict requirement for infection, and can the initiating endothelial injury be identified prospectively?

OPEN QUESTION OPEN the_thrombus_comes_first

Attached to

pathophysiology#Endothelial injury and sterile thrombus formation pathophysiology#Microbial adherence to the sterile thrombus

The standard model holds that infection requires a sterile platelet-fibrin thrombus to seed, which explains why bacteraemia is common and this disease is rare, why abnormal valves are the substrate, and why prosthetic material carries such risk. It is also why three nodes of this entry conform to the thrombogenesis module even though the disease is infectious. The model is hard to observe directly in humans, because the sterile lesion is asymptomatic and is found only incidentally or at autopsy, so the requirement is inferred from animal models and from the epidemiology rather than demonstrated prospectively. Two things follow if it is strictly true. Identifying who carries a sterile vegetation would identify who is actually at risk, which is a far better targeting strategy than the current one based on valve category. And Staphylococcus aureus, which can infect apparently normal valves, would need either an unrecognised microscopic thrombus or a genuinely distinct route of invasion, and which of those is correct is not settled.

Proposed experiments

Prospective high-resolution imaging for subclinical sterile vegetations in high-risk cohorts

exp_nbte_imaging_cohort

Image high-risk cohorts, including patients with prosthetic valves and long-term indwelling catheters, with high-resolution transoesophageal echocardiography or molecular imaging, and follow them for incident infective endocarditis. The decision criterion is whether detectable subclinical sterile vegetation predicts subsequent infection. If it does, risk targeting can move from valve category to the lesion itself.

Show evidence (1 reference)

PMID:40422904 SUPPORT Human Clinical

"This shift is of concern as it is associated with Staphylococcus Aureus which has a high virulence rate and a tendency to form a biofilm"

PARTIAL. The rise of a highly virulent organism able to affect structurally normal valves is what makes the strictness of the thrombus-first requirement an open rather than a settled question.

⚙

Pathophysiology

8

Endothelial injury and sterile thrombus formation

Turbulent flow across an abnormal valve, mechanical irritation from a catheter or prosthetic material, or inflammatory injury exposes subendothelial matrix. Platelets adhere and the coagulation cascade activates, producing a sterile fibrin-platelet thrombus known as non-bacterial thrombotic endocarditis. This step is entirely non-infectious, and it is the reason a structurally abnormal valve is a risk factor for an infectious disease.

platelet CL:0000233 endothelial cell CL:0000115

platelet aggregation GO:0070527 ↑ INCREASED blood coagulation GO:0007596 ↑ INCREASED

endocardium UBERON:0002165

Downstream

Microbial adherence to the sterile thrombus The fibrin-platelet surface provides the binding substrate that circulating organisms require in order to establish infection.

Transient bacteraemia

Organisms enter the bloodstream from dental or mucosal manipulation, injection drug use, intravascular catheters, or gut translocation. Bacteraemia is common and endocarditis is rare, which is the observation that makes the sterile thrombus a necessary condition rather than an incidental finding, and which undermines the intuitive case for antibiotic prophylaxis before dental procedures.

Downstream

Microbial adherence to the sterile thrombus Circulating organisms must be present at the same time as a receptive surface.

Microbial adherence to the sterile thrombus

Organisms bind the thrombus through surface adhesins that recognise host matrix proteins, principally fibrinogen and fibronectin. Staphylococcus aureus is particularly effective at this and is now the leading cause in much of the world, displacing the streptococci of the older literature.

cell adhesion involved in biofilm formation GO:0043708 ↑ INCREASED

Downstream

Vegetation maturation with biofilm-like protection Adherent organisms proliferate within the fibrin matrix rather than being cleared.

Show evidence (1 reference)

PMID:40422904 SUPPORT Human Clinical

"Recent studies have indicated a shift in the predominant pathogens of concern, with Streptococcus sp. a being superseded by Staphylococcus sp. and Enterococcus sp. as the leading causes of concern."

Documents the shift in causative organism, which matters mechanistically because the newer dominant organism binds and persists differently from the streptococci it displaced.

Vegetation maturation with biofilm-like protection

Continued platelet and fibrin recruitment builds a friable mass of fibrin, platelets, inflammatory cells, and dense microbial colonies. The scaffold physically excludes phagocytes and impedes antibiotic penetration, so organisms persist at high density in a site the immune system cannot reach. This is the single fact that governs treatment: it is why therapy is measured in weeks, why bactericidal agents are required, and why a sufficiently established vegetation may not be curable without excising it.

neutrophil CL:0000775

endocardium UBERON:0002165

Downstream

Local valvular and perivalvular destruction Ongoing infection at the valve destroys the tissue it sits on.

Systemic embolization of vegetation fragments The vegetation is friable and fragments detach into the circulation.

Innate immune activation and systemic inflammatory response Persistent high-density infection drives a sustained systemic inflammatory response.

Show evidence (1 reference)

PMID:40422904 SUPPORT Human Clinical

"This shift is of concern as it is associated with Staphylococcus Aureus which has a high virulence rate and a tendency to form a biofilm, meaning that non-surgical therapy may not be effective."

States both the biofilm behaviour this node describes and its therapeutic consequence, namely that medical therapy alone may fail, which is the claim that justifies curating surgery as a mechanism-directed treatment rather than a last resort.

Innate immune activation and systemic inflammatory response

Pathogen-associated molecular patterns engage pattern recognition receptors on monocytes and endothelium, driving cytokine release and inflammasome activation. This produces the fever and systemic features, and contributes to the immune complex phenomena seen in skin, retina, and kidney.

monocyte CL:0000576 macrophage CL:0000235

Local valvular and perivalvular destruction

Leaflet perforation and chordal rupture produce acute regurgitation. Extension beyond the annulus produces abscess, pseudoaneurysm, or fistula, and involvement of the conduction system produces heart block. Acute regurgitation is poorly tolerated because the ventricle has had no time to remodel, which is why this disease can decompensate over hours.

Downstream

Heart failure and haemodynamic decompensation Acute valvular incompetence imposes a sudden volume load on an unprepared ventricle.

Systemic embolization of vegetation fragments

Conformance here needs justifying, because the thrombogenesis module explicitly excludes nonthrombotic emboli. The claim is that a septic vegetation is not a nonthrombotic embolus. It is a fibrin-platelet thrombus with organisms in it, formed by the same platelet and coagulation machinery the module models, and the vascular occlusion and downstream ischaemic injury it causes are thrombotic in exactly the module's sense. The infection changes what is inside the thrombus and adds a septic dimension to the resulting infarct; it does not change the occlusive mechanism. Fragments embolise to brain, spleen, kidneys, and extremities, producing stroke, infarction, mycotic aneurysm, and peripheral lesions. Embolic stroke is both a major cause of morbidity and a complication that constrains surgery, since anticoagulation and cardiopulmonary bypass carry haemorrhagic risk in a recently infarcted brain.

Downstream

Heart failure and haemodynamic decompensation Systemic embolic and septic injury compounds cardiac decompensation.

Heart failure and haemodynamic decompensation

The terminal common pathway and the dominant determinant of early mortality, arising from acute regurgitation, myocardial abscess, conduction disturbance, and sepsis together.

Show evidence (1 reference)

PMID:19273776 SUPPORT Human Clinical

"Prospective cohort study of 2781 adults with definite IE who were admitted to 58 hospitals in 25 countries from June 1, 2000, through September 1, 2005."

Establishes the scale and international scope of the cohort that characterises modern outcomes in this disease.

⬡

Pathograph

Use the checkboxes to hide or show graph categories. Hover nodes for evidence and cross-linked metadata.

●

Phenotypes

9

Cardiovascular 5

Congestive heart failure FREQUENT HP:0001635

Show evidence (1 reference)

PMID:19273776 SUPPORT Human Clinical

"The following complications were common: stroke (16.9%), embolization other than stroke (22.6%), heart failure (32.3%), and intracardiac abscess (14.4%)."

Gives heart failure at 32.3 percent, which sits in the FREQUENT band of 30 to 79 percent.

Stroke OCCASIONAL HP:0001297

Show evidence (1 reference)

PMID:19273776 SUPPORT Human Clinical

"The following complications were common: stroke (16.9%), embolization other than stroke (22.6%), heart failure (32.3%), and intracardiac abscess (14.4%)."

Gives stroke at 16.9 percent, which sits in the OCCASIONAL band of 5 to 29 percent.

Splenomegaly HP:0001744

Intracardiac abscess OCCASIONAL Abnormal heart morphology HP:0001627

Show evidence (1 reference)

PMID:19273776 SUPPORT Human Clinical

"The following complications were common: stroke (16.9%), embolization other than stroke (22.6%), heart failure (32.3%), and intracardiac abscess (14.4%)."

Gives intracardiac abscess at 14.4 percent, in the OCCASIONAL band. The phenotype is bound to a general cardiac morphology term because HPO has no perivalvular abscess concept.

Aortic regurgitation HP:0001659

Genitourinary 1

Haematuria Hematuria HP:0000790

Metabolism 1

Fever HP:0001945

Other 2

Heart murmur HP:0030148

Mitral regurgitation HP:0001653

💊

Medical Actions

4

Prolonged intravenous antibiotic therapy

Action: Antibiotic Therapy NCIT:C15620

Bactericidal antibiotics for four to six weeks, the duration being dictated by the biofilm protection of the vegetation rather than by the organism's intrinsic susceptibility. This is the definitional treatment of the disease and the reason it carries such a burden of hospitalisation.

Mechanism Target:

INHIBITS Vegetation maturation with biofilm-like protection — Sustained bactericidal exposure is required to sterilise organisms shielded within the fibrin scaffold.

Show evidence (1 reference)

PMID:30152252 SUPPORT Human Clinical

"Patients with infective endocarditis on the left side of the heart are typically treated with intravenous antibiotic agents for up to 6 weeks."

States the standard of care that this treatment represents, and the duration that the biofilm mechanism accounts for.

Partial oral antibiotic therapy after stabilisation

Action: Antibiotic Therapy NCIT:C15620

A step-down to oral antibiotics once the patient is stable, tested against continued intravenous therapy in a randomised noninferiority trial. It is curated because it changes the practical shape of the illness rather than its biology, converting weeks of hospitalisation into outpatient treatment for suitable patients. It applies to stabilised left-sided disease caused by specific organisms, not to everyone.

Mechanism Target:

INHIBITS Vegetation maturation with biofilm-like protection — The antimicrobial target is unchanged; only the route and setting differ.

Show evidence (1 reference)

PMID:30152252 SUPPORT Human Clinical

"In a randomized, noninferiority, multicenter trial, we assigned 400 adults in stable condition who had endocarditis on the left side of the heart caused by streptococcus, Enterococcus faecalis, Staphylococcus aureus, or coagulase-negative staphylococci and who were being treated with intravenous..."

Describes the trial design and its eligibility restrictions, namely stabilised left-sided disease caused by four named organism groups, which is what bounds how far this result generalises.

Valve surgery

Action: Surgical Procedure NCIT:C15329

Excision of infected tissue with valve repair or replacement, indicated for heart failure, uncontrolled infection, abscess, or a high embolic risk. Surgery is curated here as mechanism-directed rather than as rescue, because removing the vegetation removes the protected compartment that antibiotics cannot reliably reach. Timing is genuinely difficult when embolic stroke has already occurred, since bypass and anticoagulation carry haemorrhagic risk in a recently infarcted brain.

Mechanism Target:

BYPASSES Vegetation maturation with biofilm-like protection — Excision physically removes the biofilm-protected compartment rather than attempting to penetrate it.

Show evidence (1 reference)

PMID:40422904 SUPPORT Human Clinical

"which has a high virulence rate and a tendency to form a biofilm, meaning that non-surgical therapy may not be effective"

States that biofilm formation can make medical therapy ineffective, which is the mechanistic rationale for surgery acting where antibiotics cannot.

BYPASSES Local valvular and perivalvular destruction — Repair or replacement restores valve competence after the tissue has been destroyed.

Show evidence (2 references)

PMID:31832353 SUPPORT Human Clinical

"Clinical scenarios in IE are often complex, requiring prompt diagnosis, early institution of antibiotics, and decision-making related to complications, including risk of embolism and timing of surgery when indicated."

States the surgical decision problem this treatment sits inside, and names embolic risk and timing as the factors that govern it, which is the judgement the entry describes.

PMID:31832353 SUPPORT Human Clinical

"The importance of an early, multispecialty team approach to patients with IE is emphasized."

Records the guideline emphasis on team-based decision-making, which is the practical answer to a timing question that no single specialty can resolve alone.

Antibiotic prophylaxis before dental procedures

Action: Antibiotic Therapy NCIT:C15620

Given to high-risk patients before certain dental procedures on the reasoning that procedural bacteraemia seeds the valve. The evidence for it is weak, and this treatment is curated principally to record that. The mechanistic case is intuitive and the empirical case is not established, and the discrepancy is instructive rather than embarrassing, because everyday bacteraemia from chewing and brushing plausibly dwarfs the procedural contribution.

Mechanism Target:

INHIBITS Transient bacteraemia — Prophylaxis aims to suppress procedural bacteraemia before it can seed a receptive surface.

Show evidence (1 reference)

PMID:28213367 NO_EVIDENCE Human Clinical

"The evidence base for the use of AP is limited, heterogeneous and the methodological quality of many studies is poor. Postprocedural bacteraemia is not a good surrogate endpoint for IE."

This link makes a pharmacological claim - that prophylaxis suppresses procedural bacteraemia - and the quoted sentence does not bear on it. What the sentence denies is that reducing bacteraemia predicts reduced IE, which is the bacteraemia-to-endocarditis step rather than the drug-to-bacteraemia one; if anything, using bacteraemia as a surrogate at all presumes the drug lowers it. So NO_EVIDENCE, not REFUTE. The same sentence is cited as SUPPORT in the discussion below, where the claim is that the controversy exists - one quote bearing on two different claims, which is what supports being claim-relative means.

Show evidence (1 reference)

PMID:28213367 SUPPORT Human Clinical

"Given the logistical challenges of a randomised trial, high-quality case-control studies would help to evaluate the role of dental procedures in causing IE and the efficacy of AP in its prevention."

PARTIAL. The authors' own statement that the question remains open and that a randomised trial is impractical, which is why this is likely to stay unresolved.

🌍

Environmental Factors

2

Injection drug use

ECTO:6000007 (exposure to substance abuse) is bound as the closest available term, but it names the pharmacological exposure rather than the microbiological one that matters here: the exposure hierarchy has no term expressing injection drug use as a route of microbial entry. An earlier version of this note said no term was bound; the binding was added afterwards, by the #8430 exposure-binding sweep, which did not revisit the note.

A major and growing route of entry, and the one that most changes the shape of the disease. It delivers organisms, predominantly Staphylococcus aureus, directly and repeatedly into the venous circulation, which is why it characteristically produces right-sided tricuspid disease in a structurally normal heart, unlike almost every other form of this illness.

Show evidence (3 references)

PMID:41030729 SUPPORT Human Clinical

"IE in PWID predominantly involves the right side of the heart, mainly the tricuspid valve."

States the right-sided, tricuspid-predominant distribution that this entry gives as the distinguishing consequence of the injection route.

PMID:41030729 SUPPORT Human Clinical

"Staphylococcus aureus is by far the most frequent pathogen responsible for the infection in these patients, proportionally outnumbering the prevalence of this species in non-drug users."

Supports the claim that the organism delivered by this route is predominantly Staphylococcus aureus, and that its predominance is specific to injecting patients rather than general to the disease.

PMID:35589166 SUPPORT Human Clinical

"The incidence of injection drug use-associated infective endocarditis has been increasing rapidly over the last decade."

Supports the growing half of this entry's description with a directional statement about incidence over the last decade.

Mechanism Target:

TRIGGERS Transient bacteraemia — Repeated non-sterile injection introduces organisms directly into the bloodstream.

Show evidence (1 reference)

PMID:9279330 SUPPORT Human Clinical

"Sixty-two patients were intravenous drug users (IVDU); all but 1 of these had an obvious cutaneous portal of entry related to the injection of illicit drugs."

In a prospective bacteraemia series, essentially every injecting patient had a cutaneous portal of entry attributable to injection, which is the route into the bloodstream this edge asserts. The series is of group A streptococcal bacteraemia, so it evidences the route rather than the organism that predominates in endocarditis.

Intravascular catheters and prosthetic material

No ECTO term is bound. The exposure hierarchy has no term for indwelling intravascular material as a portal of microbial entry.

Healthcare-associated disease is now a substantial share of cases. Indwelling catheters, prosthetic valves, and cardiac implantable devices supply both the endothelial injury and the portal of entry, which is why the epidemiology has shifted with the increasing use of these devices in an ageing population.

Show evidence (1 reference)

PMID:31941729 SUPPORT Human Clinical

"With an ageing population and increasing use of implantable cardiac devices and heart valves, the epidemiology of IE has changed."

Supports this entry's claim that healthcare-associated disease is now a substantial share of cases, by attributing the epidemiological shift to device use in an ageing population.

Mechanism Target:

PREDISPOSES Endothelial injury and sterile thrombus formation — Mechanical irritation from intravascular material injures endothelium and provides a non-endothelialised surface on which thrombus forms.

Show evidence (1 reference)

PMID:31941729 SUPPORT Human Clinical

"With an ageing population and increasing use of implantable cardiac devices and heart valves, the epidemiology of IE has changed."

States that device use and population ageing have changed who gets this disease, which is the claim this exposure entry makes.

🔬

Diagnosis

3

Duke-ISCVID criteria

The 2023 revision of the Duke criteria, combining microbiological, imaging, and clinical findings. Successive revisions have broadened the imaging component and the accepted organism list, reflecting both better imaging and the shift in causative organisms.

Show evidence (1 reference)

PMID:37138445 SUPPORT Human Clinical

"The resulting 2023 Duke-ISCVID IE Criteria propose significant changes, including new microbiology diagnostics (enzyme immunoassay for Bartonella species, polymerase chain reaction, amplicon/metagenomic sequencing, in situ hybridization), imaging (positron emission computed tomography with..."

Enumerates the substantive changes in the 2023 revision, including the imaging modalities and molecular microbiology that were added, which is what makes this a revision rather than a restatement.

Blood cultures

Multiple sets before antibiotics. The continuous nature of the bacteraemia, which follows from organisms proliferating on an intravascular surface, is what makes cultures drawn at any time informative and is itself a diagnostic clue.

Echocardiography

Transthoracic and, where suspicion persists, transoesophageal imaging to demonstrate the vegetation, valvular destruction, and perivalvular extension. Transoesophageal imaging is substantially more sensitive, particularly for prosthetic valves and abscess.

📈

Progression

3

Acute presentation

Staphylococcus aureus disease presents over days with high fever, rapid valve destruction, and early embolic complications. Most patients in contemporary cohorts present early rather than with the classical indolent illness.

Show evidence (1 reference)

PMID:19273776 SUPPORT Human Clinical

"Most patients (77.0%) presented early in the disease (<30 days) with few of the classic clinical hallmarks of IE."

Quantifies early presentation as the norm in the modern cohort and states that the classic hallmarks are usually absent, which is a direct departure from the textbook subacute description.

Subacute presentation

Viridans streptococcal and enterococcal disease can evolve over weeks to months with low-grade fever, weight loss, and immune phenomena, the classical picture from which the older descriptions of this disease derive.

Complication and decompensation

Heart failure from acute regurgitation, embolic stroke, perivalvular abscess with heart block, and sepsis. This is the phase in which the decision to operate is usually made, and in which the competing risks of operating and of waiting are hardest to weigh.

📊

Prevalence

1

Worldwide

Annual Incidence 1–9 per 100,000

A rare disease with high mortality. The class here is coarse because no cited source in this entry states a rate.

Show evidence (1 reference)

PMID:31941729 SUPPORT Human Clinical

"Infective endocarditis (IE) remains a rare condition but one with high associated morbidity and mortality."

PARTIAL. Establishes rarity and severity but states no rate, so the class is coarse and no numeric figure is asserted.

🦠

Infectious Agent

3

Staphylococcus aureus

Now the most common cause, displacing the streptococci of the older literature. It matters mechanistically and not just epidemiologically: it binds host matrix proteins efficiently, forms biofilm readily, and can affect structurally normal valves, which is the observation that strains the otherwise clean thrombus-first model curated in this entry.

Staphylococcus aureus NCBITaxon:1280

Show evidence (1 reference)

PMID:19273776 SUPPORT Human Clinical

"Staphylococcus aureus was the most common pathogen (31.2%)."

Quantifies its share in a prospective cohort of 2781 patients across 25 countries.

Streptococcus sanguinis

Representative of the viridans group streptococci, the classical cause of subacute disease seeded from the oral cavity. This is the organism group behind the dental prophylaxis argument curated as a controversy in this entry.

Streptococcus sanguinis NCBITaxon:1305

Enterococcus faecalis

A growing cause, particularly in older patients and after genitourinary or gastrointestinal procedures, and one of the four organism groups for which oral step-down therapy was tested.

Enterococcus faecalis NCBITaxon:1351

🔀

Differential Diagnoses

3

Conditions with similar clinical presentations that must be differentiated from Infective Endocarditis:

Rheumatic heart disease

Overlapping Features The essential distinction, and it runs both ways. Rheumatic disease is a post-infectious autoimmune sequela in which the organism is absent from the valve, whereas this is an active infection of it. They are also linked, since a rheumatic valve is exactly the kind of abnormal surface on which this disease establishes itself.

Non-bacterial thrombotic endocarditis

Overlapping Features Not merely a differential but the precursor lesion of this disease. Sterile vegetations occur in malignancy and antiphospholipid syndrome and are indistinguishable on imaging; the distinction is microbiological.

Systemic lupus erythematosus with Libman-Sacks endocarditis

Overlapping Features Produces sterile valvular vegetations with fever and multisystem features, and can be clinically indistinguishable without negative blood cultures and serology.

{ }

Source YAML

click to show

name: Infective Endocarditis
creation_date: "2026-08-10T00:20:00Z"
category: Infectious
disease_term:
  preferred_term: infective endocarditis
  term:
    id: MONDO:0000565
    label: infective endocarditis
description: >
  Microbial infection of the endocardial surface, characteristically of a valve, producing a
  vegetation of fibrin, platelets, and organisms. The disease is best understood as an infection
  that requires a thrombus first. A sterile platelet-fibrin clot forms on injured endothelium and
  only then is seeded from the bloodstream, which is why the organism alone is not sufficient and
  why the anatomical substrate matters as much as the bacteraemia. That same fibrin scaffold then
  shields the organisms from phagocytes and from antibiotic penetration, which is why treatment
  takes weeks rather than days and why surgery is sometimes the only option.
parents:
- endocardial disease
- bacterial infectious disease

classifications:
  harrisons_chapter:
  - classification_value: CARDIOVASCULAR
    notes: >-
      Curated under cardiovascular disease because the lesion, its haemodynamic consequences, and
      its surgical management are cardiac. It is equally an infectious disease, and the
      antimicrobial half of its management follows infectious disease logic rather than cardiac
      logic.

has_subtypes:
- name: Left-sided native valve
  display_name: Left-sided native valve endocarditis
  description: >
    The commonest form, affecting mitral and aortic valves on a previously abnormal or normal
    valve. It carries the embolic stroke risk, because vegetation fragments enter the systemic
    circulation, and it is the population in which oral step-down therapy was tested.
- name: Right-sided
  display_name: Right-sided endocarditis, typically tricuspid
  description: >
    Strongly associated with injection drug use, and mechanistically distinct in a way the entry's
    own prose already argued. It commonly occurs on a structurally normal valve, embolises to the
    lungs rather than the brain, and generally carries a better prognosis with medical therapy
    alone. Modelling it as a subtype rather than a variant reflects that the differences are in
    substrate, embolic destination, and outcome together.
- name: Prosthetic valve
  display_name: Prosthetic valve endocarditis
  description: >
    Infection on implanted material, where biofilm on a foreign surface makes medical cure less
    likely and perivalvular extension more common. Prosthetic involvement is an independent
    predictor of in-hospital death.
  evidence:
  - reference: PMID:19273776
    reference_title: "Clinical presentation, etiology, and outcome of infective endocarditis in the 21st century: the International Collaboration on Endocarditis-Prospective Cohort Study."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Prosthetic valve involvement (odds ratio, 1.47; 95% confidence interval, 1.13-1.90)"
    explanation: Quantifies prosthetic involvement as an independent predictor of in-hospital mortality with a confidence interval.

infectious_agent:
- name: Staphylococcus aureus
  infectious_agent_term:
    preferred_term: Staphylococcus aureus
    term:
      id: NCBITaxon:1280
      label: Staphylococcus aureus
  description: >
    Now the most common cause, displacing the streptococci of the older literature. It matters
    mechanistically and not just epidemiologically: it binds host matrix proteins efficiently,
    forms biofilm readily, and can affect structurally normal valves, which is the observation that
    strains the otherwise clean thrombus-first model curated in this entry.
  evidence:
  - reference: PMID:19273776
    reference_title: "Clinical presentation, etiology, and outcome of infective endocarditis in the 21st century: the International Collaboration on Endocarditis-Prospective Cohort Study."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Staphylococcus aureus was the most common pathogen (31.2%)."
    explanation: Quantifies its share in a prospective cohort of 2781 patients across 25 countries.

- name: Streptococcus sanguinis
  infectious_agent_term:
    preferred_term: Streptococcus sanguinis
    term:
      id: NCBITaxon:1305
      label: Streptococcus sanguinis
  description: >
    Representative of the viridans group streptococci, the classical cause of subacute disease
    seeded from the oral cavity. This is the organism group behind the dental prophylaxis argument
    curated as a controversy in this entry.

- name: Enterococcus faecalis
  infectious_agent_term:
    preferred_term: Enterococcus faecalis
    term:
      id: NCBITaxon:1351
      label: Enterococcus faecalis
  description: >
    A growing cause, particularly in older patients and after genitourinary or gastrointestinal
    procedures, and one of the four organism groups for which oral step-down therapy was tested.

pathophysiology:
- name: Endothelial injury and sterile thrombus formation
  biological_scale: TISSUE
  conforms_to: "thrombogenesis#Platelet Adhesion, Activation, and Aggregation"
  description: >
    Turbulent flow across an abnormal valve, mechanical irritation from a catheter or prosthetic
    material, or inflammatory injury exposes subendothelial matrix. Platelets adhere and the
    coagulation cascade activates, producing a sterile fibrin-platelet thrombus known as
    non-bacterial thrombotic endocarditis. This step is entirely non-infectious, and it is the
    reason a structurally abnormal valve is a risk factor for an infectious disease.
  cell_types:
  - preferred_term: platelet
    term:
      id: CL:0000233
      label: platelet
  - preferred_term: endothelial cell
    term:
      id: CL:0000115
      label: endothelial cell
  biological_processes:
  - preferred_term: platelet aggregation
    term:
      id: GO:0070527
      label: platelet aggregation
    modifier: INCREASED
  - preferred_term: blood coagulation
    term:
      id: GO:0007596
      label: blood coagulation
    modifier: INCREASED
  locations:
  - preferred_term: endocardium
    term:
      id: UBERON:0002165
      label: endocardium
  downstream:
  - target: Microbial adherence to the sterile thrombus
    causal_link_type: DIRECT
    description: >
      The fibrin-platelet surface provides the binding substrate that circulating organisms
      require in order to establish infection.

- name: Transient bacteraemia
  biological_scale: ORGANISM
  description: >
    Organisms enter the bloodstream from dental or mucosal manipulation, injection drug use,
    intravascular catheters, or gut translocation. Bacteraemia is common and endocarditis is rare,
    which is the observation that makes the sterile thrombus a necessary condition rather than an
    incidental finding, and which undermines the intuitive case for antibiotic prophylaxis before
    dental procedures.
  downstream:
  - target: Microbial adherence to the sterile thrombus
    causal_link_type: DIRECT
    description: >
      Circulating organisms must be present at the same time as a receptive surface.

- name: Microbial adherence to the sterile thrombus
  biological_scale: MOLECULAR
  description: >
    Organisms bind the thrombus through surface adhesins that recognise host matrix proteins,
    principally fibrinogen and fibronectin. Staphylococcus aureus is particularly effective at
    this and is now the leading cause in much of the world, displacing the streptococci of the
    older literature.
  biological_processes:
  - preferred_term: cell adhesion involved in biofilm formation
    term:
      id: GO:0043708
      label: cell adhesion involved in biofilm formation
    modifier: INCREASED
  downstream:
  - target: Vegetation maturation with biofilm-like protection
    causal_link_type: DIRECT
    description: >
      Adherent organisms proliferate within the fibrin matrix rather than being cleared.
  evidence:
  - reference: PMID:40422904
    reference_title: "Staphylococcus aureus Endocarditis Immunothrombosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Recent studies have indicated a shift in the predominant pathogens of concern, with Streptococcus sp. a being superseded by Staphylococcus sp. and Enterococcus sp. as the leading causes of concern."
    explanation: Documents the shift in causative organism, which matters mechanistically because the newer dominant organism binds and persists differently from the streptococci it displaced.

- name: Vegetation maturation with biofilm-like protection
  biological_scale: TISSUE
  conforms_to: "thrombogenesis#Pathological Fibrin-Platelet Thrombus Formation"
  description: >
    Continued platelet and fibrin recruitment builds a friable mass of fibrin, platelets,
    inflammatory cells, and dense microbial colonies. The scaffold physically excludes phagocytes
    and impedes antibiotic penetration, so organisms persist at high density in a site the immune
    system cannot reach. This is the single fact that governs treatment: it is why therapy is
    measured in weeks, why bactericidal agents are required, and why a sufficiently established
    vegetation may not be curable without excising it.
  cell_types:
  - preferred_term: neutrophil
    term:
      id: CL:0000775
      label: neutrophil
  locations:
  - preferred_term: endocardium
    term:
      id: UBERON:0002165
      label: endocardium
  downstream:
  - target: Local valvular and perivalvular destruction
    causal_link_type: DIRECT
    description: >
      Ongoing infection at the valve destroys the tissue it sits on.
  - target: Systemic embolization of vegetation fragments
    causal_link_type: DIRECT
    description: >
      The vegetation is friable and fragments detach into the circulation.
  - target: Innate immune activation and systemic inflammatory response
    causal_link_type: DIRECT
    description: >
      Persistent high-density infection drives a sustained systemic inflammatory response.
  evidence:
  - reference: PMID:40422904
    reference_title: "Staphylococcus aureus Endocarditis Immunothrombosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "This shift is of concern as it is associated with Staphylococcus Aureus which has a high virulence rate and a tendency to form a biofilm, meaning that non-surgical therapy may not be effective."
    explanation: States both the biofilm behaviour this node describes and its therapeutic consequence, namely that medical therapy alone may fail, which is the claim that justifies curating surgery as a mechanism-directed treatment rather than a last resort.

- name: Innate immune activation and systemic inflammatory response
  biological_scale: CELLULAR
  description: >
    Pathogen-associated molecular patterns engage pattern recognition receptors on monocytes and
    endothelium, driving cytokine release and inflammasome activation. This produces the fever and
    systemic features, and contributes to the immune complex phenomena seen in skin, retina, and
    kidney.
  cell_types:
  - preferred_term: monocyte
    term:
      id: CL:0000576
      label: monocyte
  - preferred_term: macrophage
    term:
      id: CL:0000235
      label: macrophage

- name: Local valvular and perivalvular destruction
  biological_scale: TISSUE
  description: >
    Leaflet perforation and chordal rupture produce acute regurgitation. Extension beyond the
    annulus produces abscess, pseudoaneurysm, or fistula, and involvement of the conduction system
    produces heart block. Acute regurgitation is poorly tolerated because the ventricle has had no
    time to remodel, which is why this disease can decompensate over hours.
  downstream:
  - target: Heart failure and haemodynamic decompensation
    causal_link_type: DIRECT
    description: >
      Acute valvular incompetence imposes a sudden volume load on an unprepared ventricle.

- name: Systemic embolization of vegetation fragments
  biological_scale: ORGANISM
  conforms_to: "thrombogenesis#Thrombotic Vascular Occlusion and Ischemic Tissue Injury"
  description: >
    Conformance here needs justifying, because the thrombogenesis module explicitly excludes
    nonthrombotic emboli. The claim is that a septic vegetation is not a nonthrombotic embolus. It
    is a fibrin-platelet thrombus with organisms in it, formed by the same platelet and coagulation
    machinery the module models, and the vascular occlusion and downstream ischaemic injury it
    causes are thrombotic in exactly the module's sense. The infection changes what is inside the
    thrombus and adds a septic dimension to the resulting infarct; it does not change the
    occlusive mechanism. Fragments embolise to brain, spleen, kidneys, and extremities, producing
    stroke, infarction,
    mycotic aneurysm, and peripheral lesions. Embolic stroke is both a major cause of morbidity
    and a complication that constrains surgery, since anticoagulation and cardiopulmonary bypass
    carry haemorrhagic risk in a recently infarcted brain.
  downstream:
  - target: Heart failure and haemodynamic decompensation
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >
      Systemic embolic and septic injury compounds cardiac decompensation.

- name: Heart failure and haemodynamic decompensation
  biological_scale: ORGANISM
  description: >
    The terminal common pathway and the dominant determinant of early mortality, arising from
    acute regurgitation, myocardial abscess, conduction disturbance, and sepsis together.
  evidence:
  - reference: PMID:19273776
    reference_title: "Clinical presentation, etiology, and outcome of infective endocarditis in the 21st century: the International Collaboration on Endocarditis-Prospective Cohort Study."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Prospective cohort study of 2781 adults with definite IE who were admitted to 58 hospitals in 25 countries from June 1, 2000, through September 1, 2005."
    explanation: Establishes the scale and international scope of the cohort that characterises modern outcomes in this disease.

phenotypes:
- category: Clinical
  name: Fever
  description: >
    The most common presenting feature, arising from the systemic inflammatory response to
    persistent high-density infection.
  phenotype_term:
    preferred_term: Fever
    term:
      id: HP:0001945
      label: Fever

- category: Clinical
  name: Heart murmur
  description: >
    Reflects valvular regurgitation from leaflet destruction. A new or changing murmur in a febrile
    patient is the classic combination that should raise the diagnosis.
  phenotype_term:
    preferred_term: Heart murmur
    term:
      id: HP:0030148
      label: Heart murmur

- category: Clinical
  name: Congestive heart failure
  description: >
    Usually from acute valvular regurgitation, and the dominant predictor of early mortality.
  phenotype_term:
    preferred_term: Congestive heart failure
    term:
      id: HP:0001635
      label: Congestive heart failure
  frequency: FREQUENT
  evidence:
  - reference: PMID:19273776
    reference_title: "Clinical presentation, etiology, and outcome of infective endocarditis in the 21st century: the International Collaboration on Endocarditis-Prospective Cohort Study."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The following complications were common: stroke (16.9%), embolization other than stroke (22.6%), heart failure (32.3%), and intracardiac abscess (14.4%)."
    explanation: Gives heart failure at 32.3 percent, which sits in the FREQUENT band of 30 to 79 percent.

- category: Clinical
  name: Stroke
  description: >
    Embolic, from vegetation fragments reaching the cerebral circulation. It is among the most
    consequential complications because it also complicates the decision to operate.
  phenotype_term:
    preferred_term: Stroke
    term:
      id: HP:0001297
      label: Stroke
  frequency: OCCASIONAL
  evidence:
  - reference: PMID:19273776
    reference_title: "Clinical presentation, etiology, and outcome of infective endocarditis in the 21st century: the International Collaboration on Endocarditis-Prospective Cohort Study."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The following complications were common: stroke (16.9%), embolization other than stroke (22.6%), heart failure (32.3%), and intracardiac abscess (14.4%)."
    explanation: Gives stroke at 16.9 percent, which sits in the OCCASIONAL band of 5 to 29 percent.

- category: Clinical
  name: Splenomegaly
  description: >
    A classic finding of subacute disease, reflecting chronic immune stimulation and splenic
    embolic involvement.
  phenotype_term:
    preferred_term: Splenomegaly
    term:
      id: HP:0001744
      label: Splenomegaly

- category: Laboratory
  name: Haematuria
  description: >
    From renal embolic infarction or from immune complex glomerulonephritis, which are two
    different mechanisms producing the same finding.
  phenotype_term:
    preferred_term: Hematuria
    term:
      id: HP:0000790
      label: Hematuria

- category: Clinical
  name: Intracardiac abscess
  description: >
    Perivalvular extension of infection beyond the annulus, which is both a marker of uncontrolled
    infection and an indication for surgery. It is also a strong independent predictor of death.
  phenotype_term:
    preferred_term: Abnormal heart morphology
    term:
      id: HP:0001627
      label: Abnormal heart morphology
  frequency: OCCASIONAL
  evidence:
  - reference: PMID:19273776
    reference_title: "Clinical presentation, etiology, and outcome of infective endocarditis in the 21st century: the International Collaboration on Endocarditis-Prospective Cohort Study."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The following complications were common: stroke (16.9%), embolization other than stroke (22.6%), heart failure (32.3%), and intracardiac abscess (14.4%)."
    explanation: Gives intracardiac abscess at 14.4 percent, in the OCCASIONAL band. The phenotype is bound to a general cardiac morphology term because HPO has no perivalvular abscess concept.

- category: Clinical
  name: Mitral regurgitation
  description: >
    Acute regurgitation from leaflet perforation or chordal rupture, poorly tolerated because the
    ventricle and atrium have not had time to adapt.
  phenotype_term:
    preferred_term: Mitral regurgitation
    term:
      id: HP:0001653
      label: Mitral regurgitation

- category: Clinical
  name: Aortic regurgitation
  description: >
    The aortic equivalent, and the lesion most likely to precipitate rapid decompensation.
  phenotype_term:
    preferred_term: Aortic regurgitation
    term:
      id: HP:0001659
      label: Aortic regurgitation

environmental:
- name: Injection drug use
  exposure_term:
    preferred_term: injection drug use
    term:
      id: ECTO:6000007
      label: exposure to substance abuse
  description: >
    A major and growing route of entry, and the one that most changes the shape of the disease.
    It delivers organisms, predominantly Staphylococcus aureus, directly and repeatedly into the
    venous circulation, which is why it characteristically produces right-sided tricuspid disease
    in a structurally normal heart, unlike almost every other form of this illness.
  influences_mechanisms:
  - target: Transient bacteraemia
    environmental_effect: TRIGGERS
    causal_link_type: DIRECT
    description: >
      Repeated non-sterile injection introduces organisms directly into the bloodstream.
    evidence:
    - reference: PMID:9279330
      reference_title: Group A streptococcal bacteremia. A 10-year prospective study.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Sixty-two patients were intravenous drug users (IVDU); all but 1 of these had an obvious cutaneous portal of entry related to the injection of illicit drugs."
      explanation: >
        In a prospective bacteraemia series, essentially every injecting patient had a cutaneous
        portal of entry attributable to injection, which is the route into the bloodstream this edge
        asserts. The series is of group A streptococcal bacteraemia, so it evidences the route
        rather than the organism that predominates in endocarditis.
  evidence:
  - reference: PMID:41030729
    reference_title: Infective Endocarditis in Patients With a History of Intravenous Drug Abuse.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "IE in PWID predominantly involves the right side of the heart, mainly the tricuspid valve."
    explanation: >
      States the right-sided, tricuspid-predominant distribution that this entry gives as the
      distinguishing consequence of the injection route.
  - reference: PMID:41030729
    reference_title: Infective Endocarditis in Patients With a History of Intravenous Drug Abuse.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Staphylococcus aureus is by far the most frequent pathogen responsible for the infection in these patients, proportionally outnumbering the prevalence of this species in non-drug users."
    explanation: >
      Supports the claim that the organism delivered by this route is predominantly Staphylococcus
      aureus, and that its predominance is specific to injecting patients rather than general to the
      disease.
  - reference: PMID:35589166
    reference_title: "Diagnosis and Management of Infective Endocarditis in People Who Inject Drugs: JACC State-of-the-Art Review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The incidence of injection drug use-associated infective endocarditis has been increasing rapidly over the last decade."
    explanation: >
      Supports the growing half of this entry's description with a directional statement about
      incidence over the last decade.
  notes: >
    ECTO:6000007 (exposure to substance abuse) is bound as the closest available term, but it names
    the pharmacological exposure rather than the microbiological one that matters here: the exposure
    hierarchy has no term expressing injection drug use as a route of microbial entry. An earlier
    version of this note said no term was bound; the binding was added afterwards, by the #8430
    exposure-binding sweep, which did not revisit the note.

- name: Intravascular catheters and prosthetic material
  description: >
    Healthcare-associated disease is now a substantial share of cases. Indwelling catheters,
    prosthetic valves, and cardiac implantable devices supply both the endothelial injury and the
    portal of entry, which is why the epidemiology has shifted with the increasing use of these
    devices in an ageing population.
  influences_mechanisms:
  - target: Endothelial injury and sterile thrombus formation
    environmental_effect: PREDISPOSES
    causal_link_type: DIRECT
    description: >
      Mechanical irritation from intravascular material injures endothelium and provides a
      non-endothelialised surface on which thrombus forms.
    evidence:
    - reference: PMID:31941729
      reference_title: "Infective endocarditis: A contemporary update."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "With an ageing population and increasing use of implantable cardiac devices and heart valves, the epidemiology of IE has changed."
      explanation: States that device use and population ageing have changed who gets this disease, which is the claim this exposure entry makes.
  evidence:
  - reference: PMID:31941729
    reference_title: "Infective endocarditis: A contemporary update."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "With an ageing population and increasing use of implantable cardiac devices and heart valves, the epidemiology of IE has changed."
    explanation: >
      Supports this entry's claim that healthcare-associated disease is now a substantial share of
      cases, by attributing the epidemiological shift to device use in an ageing population.
  notes: >
    No ECTO term is bound. The exposure hierarchy has no term for indwelling intravascular material
    as a portal of microbial entry.

treatments:
- name: Prolonged intravenous antibiotic therapy
  description: >
    Bactericidal antibiotics for four to six weeks, the duration being dictated by the biofilm
    protection of the vegetation rather than by the organism's intrinsic susceptibility. This is
    the definitional treatment of the disease and the reason it carries such a burden of
    hospitalisation.
  therapeutic_modality: SMALL_MOLECULE
  treatment_term:
    preferred_term: Antibiotic Therapy
    term:
      id: NCIT:C15620
      label: Antibiotic Therapy
  target_mechanisms:
  - target: Vegetation maturation with biofilm-like protection
    treatment_effect: INHIBITS
    description: >
      Sustained bactericidal exposure is required to sterilise organisms shielded within the
      fibrin scaffold.
    evidence:
    - reference: PMID:30152252
      reference_title: "Partial Oral versus Intravenous Antibiotic Treatment of Endocarditis."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Patients with infective endocarditis on the left side of the heart are typically treated with intravenous antibiotic agents for up to 6 weeks."
      explanation: States the standard of care that this treatment represents, and the duration that the biofilm mechanism accounts for.

- name: Partial oral antibiotic therapy after stabilisation
  description: >
    A step-down to oral antibiotics once the patient is stable, tested against continued
    intravenous therapy in a randomised noninferiority trial. It is curated because it changes the
    practical shape of the illness rather than its biology, converting weeks of hospitalisation
    into outpatient treatment for suitable patients. It applies to stabilised left-sided disease
    caused by specific organisms, not to everyone.
  therapeutic_modality: SMALL_MOLECULE
  treatment_term:
    preferred_term: Antibiotic Therapy
    term:
      id: NCIT:C15620
      label: Antibiotic Therapy
  target_mechanisms:
  - target: Vegetation maturation with biofilm-like protection
    treatment_effect: INHIBITS
    description: >
      The antimicrobial target is unchanged; only the route and setting differ.
  evidence:
  - reference: PMID:30152252
    reference_title: "Partial Oral versus Intravenous Antibiotic Treatment of Endocarditis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In a randomized, noninferiority, multicenter trial, we assigned 400 adults in stable condition who had endocarditis on the left side of the heart caused by streptococcus, Enterococcus faecalis, Staphylococcus aureus, or coagulase-negative staphylococci and who were being treated with intravenous antibiotics to continue intravenous treatment (199 patients) or to switch to oral antibiotic treatment (201 patients)."
    explanation: Describes the trial design and its eligibility restrictions, namely stabilised left-sided disease caused by four named organism groups, which is what bounds how far this result generalises.

- name: Valve surgery
  description: >
    Excision of infected tissue with valve repair or replacement, indicated for heart failure,
    uncontrolled infection, abscess, or a high embolic risk. Surgery is curated here as
    mechanism-directed rather than as rescue, because removing the vegetation removes the
    protected compartment that antibiotics cannot reliably reach. Timing is genuinely difficult
    when embolic stroke has already occurred, since bypass and anticoagulation carry haemorrhagic
    risk in a recently infarcted brain.
  therapeutic_modality: SURGERY
  treatment_term:
    preferred_term: Surgical Procedure
    term:
      id: NCIT:C15329
      label: Surgical Procedure
  target_mechanisms:
  - target: Vegetation maturation with biofilm-like protection
    treatment_effect: BYPASSES
    description: >
      Excision physically removes the biofilm-protected compartment rather than attempting to
      penetrate it.
    evidence:
    - reference: PMID:40422904
      reference_title: "Staphylococcus aureus Endocarditis Immunothrombosis."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "which has a high virulence rate and a tendency to form a biofilm, meaning that non-surgical therapy may not be effective"
      explanation: States that biofilm formation can make medical therapy ineffective, which is the mechanistic rationale for surgery acting where antibiotics cannot.
  - target: Local valvular and perivalvular destruction
    treatment_effect: BYPASSES
    description: >
      Repair or replacement restores valve competence after the tissue has been destroyed.
  evidence:
  - reference: PMID:31832353
    reference_title: "Current AATS guidelines on surgical treatment of infective endocarditis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Clinical scenarios in IE are often complex, requiring prompt diagnosis, early institution of antibiotics, and decision-making related to complications, including risk of embolism and timing of surgery when indicated."
    explanation: States the surgical decision problem this treatment sits inside, and names embolic risk and timing as the factors that govern it, which is the judgement the entry describes.
  - reference: PMID:31832353
    reference_title: "Current AATS guidelines on surgical treatment of infective endocarditis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The importance of an early, multispecialty team approach to patients with IE is emphasized."
    explanation: Records the guideline emphasis on team-based decision-making, which is the practical answer to a timing question that no single specialty can resolve alone.

- name: Antibiotic prophylaxis before dental procedures
  description: >
    Given to high-risk patients before certain dental procedures on the reasoning that procedural
    bacteraemia seeds the valve. The evidence for it is weak, and this treatment is curated
    principally to record that. The mechanistic case is intuitive and the empirical case is not
    established, and the discrepancy is instructive rather than embarrassing, because everyday
    bacteraemia from chewing and brushing plausibly dwarfs the procedural contribution.
  therapeutic_modality: SMALL_MOLECULE
  treatment_term:
    preferred_term: Antibiotic Therapy
    term:
      id: NCIT:C15620
      label: Antibiotic Therapy
  target_mechanisms:
  - target: Transient bacteraemia
    treatment_effect: INHIBITS
    description: >
      Prophylaxis aims to suppress procedural bacteraemia before it can seed a receptive surface.
    evidence:
    - reference: PMID:28213367
      reference_title: "Antibiotic prophylaxis for infective endocarditis: a systematic review and meta-analysis."
      supports: NO_EVIDENCE
      evidence_source: HUMAN_CLINICAL
      snippet: "The evidence base for the use of AP is limited, heterogeneous and the methodological quality of many studies is poor. Postprocedural bacteraemia is not a good surrogate endpoint for IE."
      explanation: >-
        This link makes a pharmacological claim - that prophylaxis suppresses
        procedural bacteraemia - and the quoted sentence does not bear on it. What
        the sentence denies is that reducing bacteraemia predicts reduced IE, which
        is the bacteraemia-to-endocarditis step rather than the drug-to-bacteraemia
        one; if anything, using bacteraemia as a surrogate at all presumes the drug
        lowers it. So NO_EVIDENCE, not REFUTE. The same sentence is cited as SUPPORT
        in the discussion below, where the claim is that the controversy exists -
        one quote bearing on two different claims, which is what supports being
        claim-relative means.
  evidence:
  - reference: PMID:28213367
    reference_title: "Antibiotic prophylaxis for infective endocarditis: a systematic review and meta-analysis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Given the logistical challenges of a randomised trial, high-quality case-control studies would help to evaluate the role of dental procedures in causing IE and the efficacy of AP in its prevention."
    explanation: PARTIAL. The authors' own statement that the question remains open and that a randomised trial is impractical, which is why this is likely to stay unresolved.

diagnosis:
- name: Duke-ISCVID criteria
  description: >
    The 2023 revision of the Duke criteria, combining microbiological, imaging, and clinical
    findings. Successive revisions have broadened the imaging component and the accepted organism
    list, reflecting both better imaging and the shift in causative organisms.
  evidence:
  - reference: PMID:37138445
    reference_title: "The 2023 Duke-International Society for Cardiovascular Infectious Diseases Criteria for Infective Endocarditis: Updating the Modified Duke Criteria."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The resulting 2023 Duke-ISCVID IE Criteria propose significant changes, including new microbiology diagnostics (enzyme immunoassay for Bartonella species, polymerase chain reaction, amplicon/metagenomic sequencing, in situ hybridization), imaging (positron emission computed tomography with 18F-fluorodeoxyglucose, cardiac computed tomography), and inclusion of intraoperative inspection as a new Major Clinical Criterion."
    explanation: Enumerates the substantive changes in the 2023 revision, including the imaging modalities and molecular microbiology that were added, which is what makes this a revision rather than a restatement.

- name: Blood cultures
  description: >
    Multiple sets before antibiotics. The continuous nature of the bacteraemia, which follows from
    organisms proliferating on an intravascular surface, is what makes cultures drawn at any time
    informative and is itself a diagnostic clue.

- name: Echocardiography
  description: >
    Transthoracic and, where suspicion persists, transoesophageal imaging to demonstrate the
    vegetation, valvular destruction, and perivalvular extension. Transoesophageal imaging is
    substantially more sensitive, particularly for prosthetic valves and abscess.

progression:
- phase: Acute presentation
  notes: >
    Staphylococcus aureus disease presents over days with high fever, rapid valve destruction, and
    early embolic complications. Most patients in contemporary cohorts present early rather than
    with the classical indolent illness.
  evidence:
  - reference: PMID:19273776
    reference_title: "Clinical presentation, etiology, and outcome of infective endocarditis in the 21st century: the International Collaboration on Endocarditis-Prospective Cohort Study."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Most patients (77.0%) presented early in the disease (<30 days) with few of the classic clinical hallmarks of IE."
    explanation: Quantifies early presentation as the norm in the modern cohort and states that the classic hallmarks are usually absent, which is a direct departure from the textbook subacute description.

- phase: Subacute presentation
  notes: >
    Viridans streptococcal and enterococcal disease can evolve over weeks to months with low-grade
    fever, weight loss, and immune phenomena, the classical picture from which the older
    descriptions of this disease derive.

- phase: Complication and decompensation
  notes: >
    Heart failure from acute regurgitation, embolic stroke, perivalvular abscess with heart block,
    and sepsis. This is the phase in which the decision to operate is usually made, and in which
    the competing risks of operating and of waiting are hardest to weigh.

prevalence:
- population: Worldwide
  measure_type: ANNUAL_INCIDENCE
  prevalence_class: BAND_1_9_PER_100000
  notes: >
    A rare disease with high mortality. The class here is coarse because no cited source in this
    entry states a rate.
  evidence:
  - reference: PMID:31941729
    reference_title: "Infective endocarditis: A contemporary update."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Infective endocarditis (IE) remains a rare condition but one with high associated morbidity and mortality."
    explanation: PARTIAL. Establishes rarity and severity but states no rate, so the class is coarse and no numeric figure is asserted.

differential_diagnoses:
- name: Rheumatic heart disease
  description: >
    The essential distinction, and it runs both ways. Rheumatic disease is a post-infectious
    autoimmune sequela in which the organism is absent from the valve, whereas this is an active
    infection of it. They are also linked, since a rheumatic valve is exactly the kind of abnormal
    surface on which this disease establishes itself.
- name: Non-bacterial thrombotic endocarditis
  description: >
    Not merely a differential but the precursor lesion of this disease. Sterile vegetations occur
    in malignancy and antiphospholipid syndrome and are indistinguishable on imaging; the
    distinction is microbiological.
- name: Systemic lupus erythematosus with Libman-Sacks endocarditis
  description: >
    Produces sterile valvular vegetations with fever and multisystem features, and can be
    clinically indistinguishable without negative blood cultures and serology.

discussions:
- discussion_id: prophylaxis_mechanism_evidence_gap
  kind: CONTROVERSY
  status: OPEN
  prompt: >
    Should antibiotic prophylaxis be given before dental procedures, when the mechanism is
    plausible but the evidence does not support it and a definitive trial is impractical?
  rationale: >
    The mechanistic argument is straightforward. Dental procedures cause bacteraemia, bacteraemia
    seeds a receptive endocardial surface, so suppressing the bacteraemia should prevent the
    disease. Practice guidelines have progressively narrowed the indication anyway, because the
    evidence never supported the inference. A systematic review found the evidence base limited and
    heterogeneous and, more damagingly, concluded that post-procedural bacteraemia is not a good
    surrogate for the disease, which removes the empirical link the mechanistic argument depends
    on. The plausible explanation is that cumulative everyday bacteraemia from chewing and tooth
    brushing dwarfs the procedural contribution, in which case prophylaxis targets a negligible
    fraction of exposure. This entry curates the practice with its own contradicting evidence
    attached rather than omitting it, because omission would leave the mechanistic argument
    looking unopposed. The question is unlikely to be settled, since the authors themselves note
    that a randomised trial is logistically impractical for so rare an outcome.
  attaches_to:
  - pathophysiology#Transient bacteraemia
  - treatments#Antibiotic prophylaxis before dental procedures
  evidence:
  - reference: PMID:28213367
    reference_title: "Antibiotic prophylaxis for infective endocarditis: a systematic review and meta-analysis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The evidence base for the use of AP is limited, heterogeneous and the methodological quality of many studies is poor. Postprocedural bacteraemia is not a good surrogate endpoint for IE."
    explanation: Establishes both that the direct evidence is inadequate and that the surrogate endpoint underpinning the mechanistic case is invalid.
  - reference: PMID:28213367
    reference_title: "Antibiotic prophylaxis for infective endocarditis: a systematic review and meta-analysis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Given the logistical challenges of a randomised trial, high-quality case-control studies would help to evaluate the role of dental procedures in causing IE and the efficacy of AP in its prevention."
    explanation: PARTIAL. States why the question is likely to remain open and what design could still address it, which is what makes this a standing controversy rather than a resolved negative.
  proposed_experiments:
  - experiment_id: exp_ie_prophylaxis_case_control
    name: Large linked-records case-control study of dental procedures and subsequent infective endocarditis
    description: >-
      Use linked dental and hospital records at national scale to compare recent invasive dental
      procedure exposure between incident cases and matched controls, stratified by cardiac risk
      category and prophylaxis receipt. The decision criterion is whether procedure exposure is
      associated with disease at all. If it is not, the mechanistic rationale for prophylaxis fails
      at its first step, and no trial is needed.

- discussion_id: the_thrombus_comes_first
  kind: OPEN_QUESTION
  status: OPEN
  prompt: >
    Is a pre-existing sterile thrombus a strict requirement for infection, and can the initiating
    endothelial injury be identified prospectively?
  rationale: >
    The standard model holds that infection requires a sterile platelet-fibrin thrombus to seed,
    which explains why bacteraemia is common and this disease is rare, why abnormal valves are the
    substrate, and why prosthetic material carries such risk. It is also why three nodes of this
    entry conform to the thrombogenesis module even though the disease is infectious. The model is
    hard to observe directly in humans, because the sterile lesion is asymptomatic and is found
    only incidentally or at autopsy, so the requirement is inferred from animal models and from the
    epidemiology rather than demonstrated prospectively. Two things follow if it is strictly true.
    Identifying who carries a sterile vegetation would identify who is actually at risk, which is
    a far better targeting strategy than the current one based on valve category. And Staphylococcus
    aureus, which can infect apparently normal valves, would need either an unrecognised
    microscopic thrombus or a genuinely distinct route of invasion, and which of those is correct
    is not settled.
  attaches_to:
  - pathophysiology#Endothelial injury and sterile thrombus formation
  - pathophysiology#Microbial adherence to the sterile thrombus
  evidence:
  - reference: PMID:40422904
    reference_title: "Staphylococcus aureus Endocarditis Immunothrombosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "This shift is of concern as it is associated with Staphylococcus Aureus which has a high virulence rate and a tendency to form a biofilm"
    explanation: PARTIAL. The rise of a highly virulent organism able to affect structurally normal valves is what makes the strictness of the thrombus-first requirement an open rather than a settled question.
  proposed_experiments:
  - experiment_id: exp_nbte_imaging_cohort
    name: Prospective high-resolution imaging for subclinical sterile vegetations in high-risk cohorts
    description: >-
      Image high-risk cohorts, including patients with prosthetic valves and long-term indwelling
      catheters, with high-resolution transoesophageal echocardiography or molecular imaging, and
      follow them for incident infective endocarditis. The decision criterion is whether detectable
      subclinical sterile vegetation predicts subsequent infection. If it does, risk targeting can
      move from valve category to the lesion itself.

notes: >
  Deep-research provenance. Curated from a claude_code deep-research report treated as leads only.

  Deep-research reference errors caught. Three PMIDs appearing in the report were fetched and found
  to be unrelated to this disease. PMID:25360655 is cited in the report as a study of genetic
  variants in inflammatory response genes in infective endocarditis, and the paper with that
  identifier is about establishment of animal models with coronary microcirculation. PMID:21969557
  is a paper on 9-cis-epoxycarotenoid dioxygenase in Arabidopsis thaliana seeds, and PMID:19717591
  is about FlhF GTPase activity in flagellar gene regulation. None is cited in this entry. Five
  replacement references were found by direct PubMed search and verified before use.

  Module conformance. Three nodes conform to thrombogenesis, at platelet adhesion, at fibrin-platelet
  thrombus formation, and at thrombotic occlusion with ischaemic injury. That an infectious disease
  conforms to a thrombosis module is the substantive claim of this entry rather than an artefact of
  convenience, since the sterile thrombus is a precondition for the infection rather than a
  consequence of it.

  Curated negative. Antibiotic prophylaxis before dental procedures is curated together with the
  systematic review that undermines it, including the finding that post-procedural bacteraemia is
  not a valid surrogate endpoint. The practice is recorded rather than omitted precisely so that
  the contradicting evidence has something to attach to.

  Corrected provenance claims. An earlier revision of this entry asserted that the cached abstracts
  for the partial oral therapy trial and the ICE-PCS cohort were truncated, and that the
  Duke-ISCVID record contained no abstract body. All three claims were false. The caches are
  complete, and the apparent truncation was an artefact of a fixed-width extraction window used
  during curation rather than anything in the cache. Every affected snippet has been re-quoted at
  sentence boundaries from the full cached text, which in the Duke-ISCVID case replaced a
  title-only snippet carrying no evidentiary content with the sentence enumerating the actual
  changes in the 2023 revision.

  One fetched reference is deliberately not cited. PMID:35139280, the five-year outcomes of the
  partial oral therapy trial, is a research letter whose cached record contains citation metadata
  and no abstract body. Citing it would require a title-only snippet carrying no evidentiary
  content, which is the defect corrected elsewhere in this entry, so the five-year durability of
  that result is not asserted here.

  Absent bindings. No ECTO terms are bound for injection drug use or for intravascular catheters as
  exposures, because the hierarchy has no term expressing either as a route of microbial entry, and
  the available drug-exposure terms would assert a pharmacological exposure rather than the
  microbiological one that matters here.

  NEC preflight returned SKIP, since MONDO records no causal gene for this infectious disease. The
  manual fallback was run. The preflight also reported an OMIM identifier of 154700 from the report,
  which is Marfan syndrome; inspection showed the report cites it correctly and explicitly as a
  predisposing condition several causal steps removed from the infection, not as an identifier for
  this disease, so it is not an identity mismatch.

📚

References & Deep Research

Deep Research

1

Claude Code ▸

Infective Endocarditis: Comprehensive Disease Characteristics Research Report

claude-haiku-4-5-20251001, claude-sonnet-5 36 citations 2026-08-10T00:54:20.737724

Infective Endocarditis: Comprehensive Disease Characteristics Research Report

1. Disease Information

Overview. Infective endocarditis (IE) is a life-threatening infection of the endocardial surface of the heart — most commonly the cardiac valves (native or prosthetic), but also the mural endocardium, septal defects, or indwelling intracardiac devices (pacemaker/ICD leads, prosthetic valve sewing rings). It is characterized by microbial colonization of a fibrin-platelet vegetation on damaged or abnormal endothelium, producing local tissue destruction (valve regurgitation/perforation, abscess), immune-mediated phenomena (glomerulonephritis, vasculitic skin/eye lesions), and systemic septic embolization. The StatPearls overview states plainly: "Infective endocarditis is an inflammatory condition of the endocardium, the inner lining of the heart, including the valves" (PMID not separately assigned to StatPearls chapter; NCBI Bookshelf NBK557641). A 2020 review states "Infective endocarditis (IE) is an infection of the endothelium of the heart" with an annual incidence of 3–10/100,000 population and mortality "of up to 30% at 30 days" (PMID:31941729).

Key identifiers: - MONDO: MONDO:0000565 (infective endocarditis) - OMIM: No single-gene Mendelian OMIM phenotype entry exists for IE itself (it is not a monogenic disorder); OMIM entries are relevant only for underlying predisposing structural/connective-tissue conditions (e.g., bicuspid aortic valve, Marfan syndrome, hypertrophic cardiomyopathy) - Orphanet: Not a rare/orphan disease per se (common acquired infection); Orphanet indexes it primarily under structural/valvular predisposition syndromes rather than as its own ORPHA entity - ICD-10-CM: I33.0 (Acute and subacute infective endocarditis); I38 (Endocarditis, valve unspecified); I39 (Endocarditis and heart valve disorders in diseases classified elsewhere) - ICD-11: BC63 (Infective endocarditis) - MeSH: D004696 (Endocarditis, Bacterial) / D004697 (Endocarditis, Subacute Bacterial) - Synonyms: Bacterial endocarditis, infectious endocarditis, subacute bacterial endocarditis (SBE), acute bacterial endocarditis (ABE), infective endocarditis (IE), endocarditis lenta (historical)

Data derivation. Knowledge about IE derives predominantly from aggregated disease-level clinical resources: multicenter prospective cohorts (e.g., the International Collaboration on Endocarditis — ICE-PCS registry), population-level epidemiologic surveillance (Global Burden of Disease, national hospital discharge/administrative databases), and clinical trial/guideline literature (AHA, ESC), rather than from individual case-level curated genetic databases as would apply to a monogenic disease. Some individual EHR-derived cohort statistics are cited below (e.g., Swedish national registry, U.S. NIS/IQVIA claims data).

2. Etiology

Disease Causal Factors

IE is fundamentally an infectious disease requiring two converging processes: (1) an abnormal/damaged endocardial surface that generates a nidus of sterile platelet-fibrin thrombus (non-bacterial thrombotic endocarditis, NBTE), and (2) transient or sustained bacteremia/fungemia that seeds that nidus. It is not a genetic (Mendelian) disease, but genetic and structural cardiac factors substantially modify individual risk.

Causative microorganisms and approximate proportions (PMID:31941729; StatPearls NBK557641; PMC6964163): - Staphylococcus aureus — ~26.6–30% of cases (now the single most common pathogen overall, and dominant in healthcare-associated/IVDU-associated IE); associated with the most aggressive, acute presentation and worst outcomes - Viridans group streptococci (S. sanguinis, S. mitis, S. oralis, S. mutans, etc.) — ~18.7–20%; classic cause of subacute native-valve, community-acquired IE originating from the oral cavity - Other streptococci (including Streptococcus gallolyticus [bovis], associated with colonic neoplasia) — ~17.5% - Enterococci (E. faecalis, E. faecium) — ~10.5%, increasing in proportion, linked to rising antimicrobial use and healthcare exposure - Coagulase-negative staphylococci (S. epidermidis and others) — dominant cause of early prosthetic-valve IE - HACEK organisms (Haemophilus, Aggregatibacter [formerly Actinobacillus], Cardiobacterium, Eikenella, Kingella) — fastidious oral-cavity Gram-negative commensals, a classic cause of culture-negative or slow-growing-culture IE - Fungi (predominantly Candida spp., especially C. albicans, also C. parapsilosis, C. tropicalis, C. glabrata) — ~1–3% of all IE but with mortality >70% hospital-mortality rates cited at 33–47%; strongly associated with prosthetic valves, cardiac implantable devices, and injection drug use - Culture-negative organisms requiring specialized serology/PCR: Coxiella burnetii (Q fever — "the most frequent etiological agent of blood culture-negative infective endocarditis worldwide"), Bartonella spp. (B. henselae, B. quintana — biofilm-associated, linked to homelessness/body lice exposure), Tropheryma whipplei (Whipple disease), Brucella spp., Legionella, and non-Candida fungi - "Together [staphylococci, streptococci, and enterococci] account for 80–90% of all cases" (PMID:31941729)

Risk Factors

Genetic/host risk factors: - Congenital structural cardiac lesions: bicuspid aortic valve (BAV; prevalence 0.5–2.0% of the population, IE incidence 1.8–2% in BAV patients, "the risk of IE can be increased more than 140 times by congenital heart disease"), unrepaired cyanotic congenital heart disease, ventricular septal defect, patent ductus arteriosus - Connective-tissue/valvulopathy syndromes predisposing via myxomatous degeneration: mitral valve prolapse (MVP), Marfan syndrome (FBN1), Loeys-Dietz syndrome - Prior rheumatic heart disease (chronic streptococcal valvular scarring) - Hypertrophic obstructive cardiomyopathy (turbulent flow across LVOT) - Host innate-immunity gene polymorphisms modifying susceptibility once bacteremic: functional variants in TLR2 and TLR5 ("TLR polymorphisms... have been strongly associated with increased susceptibility to IE"), IL6 (the IL6 c.471+870G>A genotype associated with increased susceptibility), IL1B, IL10, IL12B, TNF, SELE (E-selectin), and ICAM1, implicating dysregulated innate immunity/cytokine signaling and endothelial adhesion pathways (PMID:25360655 [Genetic Variants in Genes of the Inflammatory Response in Association with Infective Endocarditis, PLOS ONE]). A genome-wide association study of S. aureus native-valve IE (67 cases vs. 72 S. aureus-bacteremic controls without IE) identified four SNPs on chromosome 3 approaching but not reaching genome-wide significance (P<1×10⁻⁵), underscoring that host genetic architecture of susceptibility remains incompletely defined (PMC5893849).

Environmental/acquired risk factors: - Injection drug use (IDU/IVDU): "a 50- to 100-fold higher incidence of IE compared to the general population," via endothelial injury from injected particulate matter, direct inoculation of skin/oral flora (notably S. aureus), and vasospasm-induced intimal damage; disproportionately causes right-sided (tricuspid) IE - Prosthetic heart valves (mechanical or bioprosthetic): incidence 0.3–1.2% per patient-year; highest risk in the first 6–12 months post-implantation (early PVE, dominated by coagulase-negative staphylococci and perioperative contamination) vs. late PVE (organism spectrum resembling native-valve IE) - Cardiac implantable electronic devices (CIEDs): pacemakers, ICDs — lead-associated infection and device-pocket seeding - Chronic hemodialysis (repeated vascular-access bacteremia) - Poor dentition/periodontal disease and invasive dental procedures (viridans streptococcal bacteremia) - Advanced age (rising incidence in the 55+ population — see Epidemiology) - Immunocompromised states, including HIV infection, diabetes mellitus (affecting up to one-third of North American IE patients), chronic liver disease, malignancy - Indwelling central venous catheters, healthcare-associated bacteremia, recent cardiac surgery/transcatheter valve implantation (TAVI) - Male sex (male:female ratio ~3:2, ranging 3:2 to 9:1 across series)

Protective Factors

No well-established genetic protective variants have been robustly replicated for IE specifically. General protective factors are indirect: good oral hygiene/regular dental care (reduces bacteremic seeding events), harm-reduction practices in people who inject drugs (sterile injection equipment, supervised consumption sites — reduces endothelial injury and inoculation), prompt treatment of S. aureus bacteremia to prevent secondary valve seeding, and (controversially) antibiotic prophylaxis before invasive dental procedures in high-risk cardiac-lesion patients (discussed under Prevention).

Gene-Environment Interactions

The clearest gene-environment interaction model in IE is a "two-hit" framework: an anatomic/structural or genetically-determined endocardial abnormality (bicuspid valve, MVP, prosthetic material) creates the substrate for NBTE formation, while an environmentally-determined bacteremic event (dental procedure, IDU, catheter-associated infection, dialysis access) provides the inoculum. Superimposed on this, polymorphisms in innate-immune genes (TLR2/TLR5, IL6, IL10) appear to modulate whether transient bacteremia in a structurally predisposed host progresses to established valvular infection versus is cleared — i.e., a genetic modifier of the environmentally-triggered infectious event, rather than a primary causal genetic lesion.

3. Phenotypes

IE phenotypes span constitutional/systemic symptoms, cardiac signs, immune-complex-mediated peripheral stigmata, embolic phenomena, and laboratory abnormalities.

Phenotype	Type	Frequency	Onset/Course	HPO term (suggested)
Fever	Symptom/sign	>95% of cases ("Fever...is present in more than 95% of cases")	Acute (S. aureus) or subacute/low-grade (viridans strep); often the presenting complaint	HP:0001945 (Fever)
New or changing heart murmur	Clinical sign	~48–85% (varies by valve/organism)	Progressive as vegetation/regurgitation worsens	HP:0031264 (Cardiac murmur)
Splinter hemorrhages	Physical/dermatologic sign	~15% (nonspecific)	Subacute; immune-complex or micro-embolic	HP:0100651 (Nail dysplasia) — no exact term; closest is HP:0040242 (splinter hemorrhage not in core HPO; consider free-text)
Osler nodes	Physical sign	~3–15%, more with subacute disease	Tender, painful, immune-complex-mediated	HP:0100547 (Osler node — not standard HPO ID; confirm via OAK lookup)
Janeway lesions	Physical sign	~5–10%	Non-tender, embolic/microabscess-mediated, seen more in acute S. aureus IE	HP:0200042 (Skin ulcer) — nearest generic; verify precise term
Roth spots	Ocular sign	~2–10%	Retinal hemorrhage with pale center, immune-complex-mediated	HP:0025230 (Roth spot)
Splenomegaly	Sign	~20–40%	Subacute/chronic disease	HP:0001744 (Splenomegaly)
Petechiae (conjunctival/mucosal/extremity)	Sign	~20–40%	Variable	HP:0000967 (Petechiae)
Glomerulonephritis (immune-complex)	Renal/laboratory	Variable, part of classic triad	Subacute course	HP:0000099 (Glomerulonephritis)
Arthralgia/myalgia	Symptom	~15–30%	Nonspecific systemic	HP:0002829 (Arthralgia)
Weight loss/malaise/night sweats	Constitutional symptom	Common in subacute disease	Insidious	HP:0001824 (Weight loss); HP:0001744
Acute/worsening heart failure	Clinical sign/complication	Leading cause of morbidity and the "dominant predictor for 30-day mortality"	Can be abrupt (acute regurgitation, chordal rupture)	HP:0001635 (Congestive heart failure)
Embolic stroke/neurological event	Complication	15–30% (up to 60% with vegetations >30mm)	Can be presenting event	HP:0001297 (Stroke)
Anemia (normocytic, of chronic disease)	Laboratory abnormality	Common in subacute IE	Progressive with disease duration	HP:0001903 (Anemia)
Elevated inflammatory markers (CRP, ESR)	Laboratory abnormality	Near-universal	—	HP:0011227 (Elevated CRP — verify OAK term); HP:0003565
Positive blood cultures/bacteremia	Laboratory/microbiologic	Major Duke criterion	—	(Not typically HPO-coded; a laboratory/microbiologic finding)
Mycotic (infectious) aneurysm	Vascular complication	~2–10%	Can present late, sometimes after treatment	HP:0004944 (Aneurysm)

Quality-of-life impact: IE carries substantial acute morbidity (prolonged hospitalization, IV antibiotic courses of 4–6+ weeks, frequent cardiac surgery), and survivors — particularly those with embolic stroke, heart failure, or valve replacement — face lasting functional impairment; formal disease-specific QoL instrument data (EQ-5D/SF-36) are sparse in the IE literature relative to chronic diseases, reflecting its status as an acute, often curable infection rather than a chronic condition, though post-stroke and post-cardiac-surgery patients experience durable QoL decrements documented in the broader stroke/cardiac-surgery literature.

4. Genetic/Molecular Information

IE is not a monogenic disease — there are no "causal genes" in the OMIM/ClinVar sense analogous to a Mendelian disorder. Genetic information relevant to IE falls into three categories:

(a) Host susceptibility loci (modifier, not causal, and typically common variants of modest effect): - TLR2 (HGNC:11848) and TLR5 (HGNC:11851) polymorphisms — associated with increased IE susceptibility via impaired peptidoglycan/lipoteichoic-acid/flagellin sensing - IL6 (HGNC:6018) c.471+870G>A — associated with increased susceptibility - IL1B (HGNC:5992), IL10 (HGNC:6018... actually HGNC:5962), IL12B (HGNC:5970), TNF (HGNC:11892), SELE (HGNC:10718), ICAM1 (HGNC:5344) — inflammatory-response gene variants studied for association (PMID:25360655) - A dedicated GWAS of S. aureus native-valve IE (PMC5893849) found suggestive (not genome-wide-significant) chromosome-3 loci, indicating the field lacks a robustly replicated common-variant architecture and larger studies are needed - Functional consequence framing: these are population susceptibility/modifier alleles, not deterministic pathogenic variants — none currently meet ACMG/AMP pathogenicity criteria because there is no monogenic Mendelian trait to classify against

(b) Predisposing-condition genes (genes causal for the structural substrate, not for IE itself): e.g., FBN1 (Marfan syndrome, OMIM:154700), TGFBR1/TGFBR2 (Loeys-Dietz syndrome), genes underlying bicuspid aortic valve (NOTCH1, GATA5, SMAD6) and hypertrophic cardiomyopathy (MYH7, MYBPC3) — these create the anatomic nidus but are several causal steps removed from the infection itself.

(c) Pathogen-side molecular determinants — the mechanistically central "genetics" of IE lies in the microbial virulence factors, not the human genome: - Sortase A (SrtA) — a S. aureus transpeptidase that covalently anchors LPXTG-motif surface proteins (MSCRAMMs) to peptidoglycan; essential for surface display of adhesins - MSCRAMMs (Microbial Surface Components Recognizing Adhesive Matrix Molecules): ClfA (clumping factor A, binds fibrinogen), FnBPA/FnBPB (fibronectin-binding proteins A/B, bind fibronectin/fibrinogen/elastin and mediate both initial colonization and endothelial-cell invasion), and Cna (collagen-binding adhesin). "Experiments employing heterologous expression of the staphylococcal MSCRAMMs clumping factor A (ClfA) and fibronectin binding protein A (FnbA) in Lactococcus lactis suggest that these proteins mediate initial colonization and invasiveness, respectively, in staphylococcal IE." Polymorphisms in fnbA are associated with cardiovascular-device infection risk (PNAS PMID:21969557, PMC of PMID:21969557). - von Willebrand factor-binding protein (vWbp) and coagulase — staphylococcal factors implicated in vegetation formation, though a rat catheter-model study found only a "marginal role" for these specific factors in initiating vegetation (PMC7000203) - Streptococcal MSCRAMMs/pilus adhesins in Streptococcus gallolyticus (S. bovis group) — Acb (collagen-binding adhesin) and related pilus proteins (PMID:19717591, J Bacteriol) - Epigenetics: Limited data exist on valve-tissue epigenetic changes in IE specifically; transcriptomic (not epigenomic) profiling has been the dominant molecular-profiling approach (see below). - Chromosomal abnormalities: Not applicable to IE as an infectious process (no karyotypic/CNV etiology), aside from the CNVs/structural variants underlying some predisposing congenital cardiac lesions.

5. Environmental Information

Environmental/exposure factors: Contaminated injection drug paraphernalia (bacterial and fungal inoculation); indwelling foreign material (catheters, prosthetic valves, CIEDs) providing a surface for biofilm formation; healthcare exposures (hemodialysis, recent hospitalization, invasive procedures)
Lifestyle factors: Injection drug use is the dominant modifiable lifestyle risk factor, with a shifting demographic — "most opioid use disorder-associated IE hospitalizations [2016–2020] were among females, in stark contrast with IE due to other causes" — reflecting the opioid epidemic's changing face; poor dental hygiene; homelessness and body-lice exposure (risk factor specifically for Bartonella quintana IE, "trench fever" organism)
Infectious agents (primary etiology, detailed in §2): Gram-positive cocci (S. aureus, viridans/other streptococci, enterococci, coagulase-negative staphylococci) dominate; Gram-negative HACEK organisms and fungi (Candida spp.) are less common but clinically important; zoonotic/atypical agents (Coxiella burnetii, Bartonella spp., Brucella spp.) cause a meaningful fraction of culture-negative IE and require specific serologic/molecular diagnostics (indirect immunofluorescence for Coxiella, EIA/PCR for Bartonella).

6. Mechanism / Pathophysiology

Causal Chain (Initial Trigger → Clinical Manifestation)

Step 1 — Endothelial injury and NBTE formation (initiating, upstream): Endocardial trauma from turbulent blood flow (across a stenotic/regurgitant/bicuspid valve), mechanical irritation from a catheter or prosthetic material, or immune-complex/vasculitic injury exposes the subendothelial extracellular matrix (collagen, fibronectin, tissue factor). This activates platelets and the coagulation cascade, producing a sterile fibrin-platelet thrombus — non-bacterial thrombotic endocarditis (NBTE). As one review states: "Infective endocarditis is initiated by an endothelial injury that results in exposure of the subendothelial extracellular matrix that activates platelets and causes the formation of a fibrin-platelet clot" (Merck/StatPearls synthesis); "the damaged endocardium then serves as a nidus for platelet aggregation and activation of the coagulation cascade, resulting in sterile, nonbacterial thrombotic vegetations" (NBK557641).

Step 2 — Transient bacteremia and microbial adherence (trigger event): A bacteremic or fungemic episode (dental manipulation, IDU injection, catheter contamination, gut/mucosal translocation) delivers circulating organisms that adhere to the NBTE surface via pathogen-encoded MSCRAMMs (ClfA, FnBPA/B binding fibrinogen/fibronectin) — "subsequently, microorganisms in the blood adhere to the fibrin-platelet clot to initiate vegetation formation in infective endocarditis."

Step 3 — Bacterial proliferation, biofilm formation, and vegetation maturation (CELLULAR/MOLECULAR): Adherent organisms proliferate within the fibrin matrix, are shielded from host phagocytes and antibiotic penetration by the fibrin/platelet scaffold (biofilm-like protection), and continue to recruit platelets/fibrin, producing a mature, friable vegetation composed of fibrin, platelets, inflammatory cells, and dense microbial colonies.

Step 4 — Host innate immune activation (parallel, CELLULAR): Pathogen-associated molecular patterns (peptidoglycan, lipoteichoic acid via TLR2; LPS via TLR4) engage pattern-recognition receptors on monocytes/endothelium, triggering MyD88-dependent NF-κB signaling, pro-inflammatory cytokine release (IL-1β, IL-6, TNF-α), and NLRP3 inflammasome activation with caspase-1-mediated maturation of IL-1β/IL-18 — driving both local tissue inflammation and the systemic inflammatory/febrile response. Complement activation (membrane attack complex assembly) further amplifies endothelial NLRP3 inflammasome activity in IFN-γ-primed endothelium.

Step 5 — Local tissue destruction (TISSUE, downstream): Ongoing infection causes valve leaflet perforation, chordal rupture, and can extend beyond the valve annulus to form paravalvular/myocardial abscesses, pseudoaneurysms, or fistulae — mechanically producing valvular regurgitation/stenosis.

Step 6 — Systemic embolization and immune-complex deposition (ORGANISM, downstream): Fragments of the friable vegetation embolize to the brain (stroke, mycotic aneurysm), spleen, kidneys, and extremities (Janeway lesions), while circulating immune complexes deposit in skin (Osler nodes), retina (Roth spots), and glomeruli (immune-complex glomerulonephritis).

Step 7 — Hemodynamic decompensation and multiorgan complications (ORGANISM, terminal common pathway): Acute valvular regurgitation and/or myocardial abscess/conduction-system involvement (AV block) precipitate heart failure; sepsis, embolic stroke, and renal failure compound systemic decompensation — "heart failure and compromised hemodynamic status are identified as the dominant predictors for 30-day mortality."

Cell Types and Biological Processes Involved

Platelets (CL:0000233) — initial NBTE scaffold formation, aggregation
Endothelial cells (CL:0000115) — injury/dysfunction, NLRP3 activation, adhesion molecule (E-selectin/ICAM-1) upregulation
Monocytes/macrophages (CL:0000576/CL:0000235) — pathogen recognition, inflammasome activation, phagocytosis (often evaded within biofilm)
Neutrophils (CL:0000775) — recruited to vegetation, contribute to local tissue damage
Fibroblasts/myofibroblasts — organizing/healing response in chronic vegetations
Relevant GO Biological Process terms: GO:0007596 (blood coagulation), GO:0030193 (regulation of blood coagulation), GO:0002376 (immune system process), GO:0006954 (inflammatory response), GO:0043123 (positive regulation of I-kappaB kinase/NF-kappaB signaling), GO:0043312 (neutrophil degranulation), GO:0002250 (adaptive immune response — for immune-complex phenomena), GO:0007599 (hemostasis)

Molecular Profiling Data

Transcriptomics: "The Transcriptional Programme of Human Heart Valves Reveals the Natural History of Infective Endocarditis" (PMID:20126625) profiled gene expression in excised human IE valve tissue, characterizing the local transcriptional response and its temporal evolution during disease.
Proteomics/metabolomics/lipidomics: No large-scale disease-specific datasets identified in this search; represents a research gap relative to genomics/transcriptomics.
Genomic structural features: Not applicable at the host level (non-Mendelian); pathogen genomic epidemiology (e.g., S. aureus clonal complex typing, agr locus variants) is an active research area for virulence correlation.

7. Anatomical Structures Affected

Organ level: - Primary: Heart — endocardium, cardiac valves (mitral most common in native-valve left-sided IE overall; aortic valve predominant in bicuspid-valve-associated IE; tricuspid valve predominant in IVDU-associated right-sided IE), chordae tendineae, papillary muscles, interventricular septum (in VSD-associated IE), and prosthetic valve material/annular sewing ring - Secondary (embolic/immune complications): Brain (embolic stroke, mycotic aneurysm, abscess), spleen (infarct, abscess), kidney (infarct, immune-complex glomerulonephritis), lung (septic pulmonary emboli — classic in right-sided/tricuspid IE), skin (Osler nodes, Janeway lesions, petechiae), eye/retina (Roth spots), peripheral/visceral arteries (mycotic aneurysm), musculoskeletal system (septic arthritis, vertebral osteomyelitis/discitis) - Body systems involved: Cardiovascular (primary), nervous (embolic/inflammatory CNS complications), renal, immune, dermatologic, ocular, musculoskeletal

Tissue and cell level: - Valvular endothelium/subendothelial connective tissue — site of NBTE and infection - Vascular endothelium (systemic) — target of embolic and immune-complex injury - Renal glomerular basement membrane/mesangium — immune-complex deposition

Subcellular level: - Platelet cytoplasmic granules (release reaction feeding NBTE) - Endothelial cell plasma membrane (TLR/adhesion molecule expression), cytoplasm (NLRP3 inflammasome assembly), and, in host inflammatory cells, mitochondria (oxidative burst) - Relevant GO Cellular Component: GO:0005886 (plasma membrane), GO:0032991 (protein-containing complex, for the NLRP3 inflammasome), GO:0070062 (extracellular exosome, relevant to platelet-derived microparticles)

Localization/UBERON terms (suggested): - UBERON:0000948 (heart) - UBERON:0002332 (mitral valve) - UBERON:0002137 (aortic valve) - UBERON:0002136 (tricuspid valve) - UBERON:0002094 (endocardium) - UBERON:0000955 (brain) — embolic complications - UBERON:0002106 (spleen) - UBERON:0002113 (kidney) - UBERON:0001981 (blood vessel) — mycotic aneurysm

Lateralization: Left-sided IE (mitral/aortic) is more common overall and community-associated; right-sided IE (tricuspid, sometimes pulmonic) is strongly associated with IVDU and CIED lead infection.

8. Temporal Development

Onset: - Age of onset spans the full adult lifespan, with a marked shift toward older age over recent decades (see Epidemiology); pediatric IE is uncommon (estimated 0.43–0.69 cases per 100,000 children) but occurs mainly in children with congenital heart disease or indwelling catheters/central lines, typically school-age children and adolescents, more often male - Onset pattern: Classically dichotomized into acute (rapid, fulminant, typically S. aureus, high fever, rapid valve destruction, days to 1–2 weeks to presentation) and subacute (indolent, typically viridans streptococci or HACEK organisms, low-grade fever, weeks to months of nonspecific constitutional symptoms — historically termed "subacute bacterial endocarditis")

Progression: - Disease stages (informal, not a formal staging system like cancer): early localized valvular infection → local extension (annular abscess, fistula) → systemic embolic/immune-complex phase → multiorgan complications/sepsis - Progression rate: Rapid in acute S. aureus IE (valve destruction and hemodynamic collapse can occur within days); slow/insidious in subacute viridans-streptococcal or Coxiella/culture-negative disease (weeks to months, occasionally presenting as chronic Q fever endocarditis over years) - Disease course pattern: Typically a single acute/subacute infectious episode treated to cure with antibiotics ± surgery, though relapse (within ~6 months, same organism) and reinfection (new episode, often different organism, especially in IVDU/dialysis/prosthetic-valve populations) are well described; not classically relapsing-remitting in the autoimmune sense - Disease duration: Self-limited with appropriate treatment for most native-valve cases (4 weeks IV antibiotics); prosthetic-valve and complicated cases require 6+ weeks and often surgery; without treatment, IE is essentially uniformly fatal

Patterns: - Remission: Treatment-induced (antibiotics ± surgical source control); spontaneous resolution is exceedingly rare and disease is not considered self-remitting - Critical periods: The first 2 weeks of antibiotic therapy carry the highest risk of embolic events and hemodynamic decompensation, making this the critical intervention window for surgical timing decisions in patients with large/mobile vegetations or heart failure; the first 6–12 months post-prosthetic-valve-implantation is the critical period of highest risk for early PVE.

9. Inheritance and Population

Epidemiology

Global incidence: 3–10 per 100,000 population per year (PMID:31941729)
United States trend: Age-standardized incidence rate (ASIR) rose from 10.2/100,000 in 1990 to 14.4/100,000 in 2019 — a 41% relative increase; increase greater in men (45.8%) than women (34.1%); driven almost entirely by the 55+ age group (112.7% relative increase in that stratum), while incidence among 5–19 year-olds fell 36.6% over the same 30-year period (American Journal of Cardiology, 2023 analysis of Global Burden of Disease data)
Mortality: 30-day all-cause mortality ~10.4% in some cohorts; in-hospital mortality commonly cited 15–30% (up to ~18% in one large series, approaching 30% in early prosthetic-valve IE); one-year mortality approaching 40% in some series; post-treatment survival ~85–90% at 1 year and 70–80% at 5 years per ESC guideline synthesis

Genetic Etiology Parameters

Because IE is an acquired infectious disease rather than a Mendelian trait, classic Mendelian-genetics parameters (inheritance pattern, penetrance, expressivity, anticipation, germline mosaicism, founder effect, carrier frequency) do not directly apply. What is heritable/population-structured is host susceptibility (innate-immune gene polymorphisms noted in §4) and the structural cardiac lesions that predispose to it (which do follow AD/AR/multifactorial inheritance in their own right — e.g., bicuspid aortic valve shows a multifactorial/oligogenic pattern with ~9% familial recurrence and identified genes including NOTCH1).

Population Demographics

Sex ratio: Male predominance, ~3:2 in most series (range 3:2–9:1 depending on cohort/organism); notable recent reversal in opioid-associated IE, where most 2016–2020 U.S. hospitalizations were among females
Age distribution: Bimodal historically (rheumatic-heart-disease-associated young adults vs. degenerative-valve-disease-associated elderly), now heavily weighted toward older adults (55+) in high-income countries due to declining rheumatic fever and rising prosthetic valve/device use and healthcare-associated bacteremia; younger, IVDU-associated peak in some U.S. regions during the opioid epidemic
Geographic distribution: Regional disparities documented within the U.S. (Gender, Age, and Regional Disparities study, Am J Cardiol 2023); globally, Coxiella burnetii IE shows marked geographic clustering (Mediterranean basin, parts of the Middle East and Asia) reflecting Q fever endemicity; rheumatic-heart-disease-associated IE remains disproportionately common in low- and middle-income countries
Affected/at-risk populations: People who inject drugs, hemodialysis patients, patients with prosthetic valves/CIEDs, older adults with degenerative valve disease, patients with congenital heart disease (particularly bicuspid aortic valve)

10. Diagnostics

Clinical Tests

Blood cultures: Cornerstone of diagnosis. "Antimicrobial therapy should generally not be commenced until three sets of blood cultures have been taken; this will detect bacteraemia successfully in up to 98% of cases." LOINC-coded (e.g., LOINC:600-7 for blood culture)
Inflammatory/laboratory markers: CRP, ESR, procalcitonin (PCT — "strictly tied with S. aureus etiology" and "the best predictor of poor clinical outcome"), complete blood count (anemia, leukocytosis), rheumatoid factor (immune-complex marker), complement levels (low in immune-complex glomerulonephritis), urinalysis (hematuria/proteinuria)
Cardiac biomarkers (prognostic): NT-proBNP (independent predictor of in-hospital mortality, OR 14.9 in one study; levels <2926 pg/mL had 96.6% negative predictive value for favorable outcome), cardiac troponin, pro-adrenomedullin and copeptin (associated with worse prognosis)
Imaging:
Transthoracic echocardiography (TTE) — first-line
Transesophageal echocardiography (TEE) — higher sensitivity for vegetations/abscess, standard in suspected/complex cases; "both TTE and TEE can provide normal or inconclusive findings in up to 30% of cases, especially in patients with prosthetic devices"
Cardiac CT/CT angiography — best for assessing perivalvular abscess/pseudoaneurysm
¹⁸F-FDG PET/CT — recommended especially for possible prosthetic-valve IE, "to both detect valvular lesions and confirm the diagnosis," and best for cardiac device infection and extracardiac septic foci
Multimodality comparative performance: "Echocardiography performed best in the assessment of vegetations...MDCTA performed best in the assessment of abscesses, and FDG-PET/CT performed best in the assessment of cardiac device infection, extracardiac infectious foci, and alternative diagnoses"
Histopathology (surgical/autopsy specimens): Vegetation histology showing fibrin, platelets, inflammatory infiltrate, and organisms; valve tissue Gram stain and culture

Genetic Testing

Not applicable as a diagnostic modality for IE itself (non-Mendelian). Molecular diagnostics are pathogen-directed rather than host-genome-directed: - PCR/broad-range 16S rRNA sequencing and metagenomic/amplicon sequencing of excised valve tissue or blood — critical for culture-negative IE (fastidious/intracellular organisms) - Serology/EIA for Coxiella burnetii (phase I/II antibody titers — gold standard for Q fever endocarditis) and Bartonella spp. - In situ hybridization on valve tissue — newly incorporated in the 2023 Duke-ISCVID criteria

Clinical Criteria — the Duke/Duke-ISCVID Criteria

Modified Duke criteria (2000): Definite IE requires 2 major, or 1 major + 3 minor, or 5 minor criteria; major criteria = positive blood cultures (typical organism from 2 separate cultures, or persistently positive cultures) + evidence of endocardial involvement (echocardiographic vegetation/abscess/new dehiscence, or new valvular regurgitation); minor criteria include predisposing heart condition or IVDU, fever ≥38°C, vascular phenomena (emboli, mycotic aneurysm, Janeway lesions), immunologic phenomena (glomerulonephritis, Osler nodes, Roth spots, rheumatoid factor), and microbiologic evidence not meeting major criteria. Sensitivity ~80% overall, "significantly lower in cases of prosthetic valve endocarditis."
2023 Duke-ISCVID criteria (PMID:37138445, Clinical Infectious Diseases 77(4):518–526, lead author Vance G. Fowler): Major revision adding (1) new microbiologic modalities — Bartonella EIA, PCR, amplicon/metagenomic sequencing, in situ hybridization; (2) advanced imaging — ¹⁸F-FDG PET/CT and cardiac CT; (3) intraoperative inspection as a new Major Clinical Criterion within a newly created surgical domain (added to the pre-existing microbiologic and imaging domains); (4) an expanded "typical organism" list, with certain pathogens counted as typical only in the presence of intracardiac prosthetic material; (5) simplified blood-culture timing requirements (removed the requirement for strict timing and separate venipuncture sites); (6) clarified predisposing conditions to explicitly include transcatheter valve implants and endovascular CIEDs. Reported sensitivity 89.4% vs. 87.9% for the 2015 ESC-modified Duke criteria in a comparative cohort.
Differential diagnosis: Non-bacterial thrombotic (marantic) endocarditis, Libman-Sacks endocarditis (SLE/antiphospholipid syndrome), rheumatic valvulitis, atrial myxoma, degenerative valve calcification with sterile vegetation-mimicking lesions, culture-negative "aseptic" post-infectious endocarditis.

Screening

No population-based screening program exists for IE (it is an acute infectious event, not amenable to presymptomatic screening); the closest analog is targeted surveillance/echocardiographic monitoring in known high-risk populations (e.g., IVDU with recurrent bacteremia, hemodialysis patients with recurrent access infections) and pre-procedural risk stratification for prophylaxis decisions (see Prevention).

11. Outcome/Prognosis

Survival and Mortality

30-day mortality: ~10.4% in one large contemporary cohort; up to 30% cited in other series
In-hospital mortality: ~15–30% overall, "approximately 18%" in one cited series, with early prosthetic-valve endocarditis carrying the highest mortality (~30%)
One-year mortality: approaching 40% in some cohorts
Post-treatment survival (ESC guideline synthesis): 85–90% at 1 year, 70–80% at 5 years
Sex/age trends in mortality are an active research area (JACC: Advances 2025, PMC12271061 — "Impact of Sex and Age on Trends of Mortality From Infective Endocarditis in High-Income Countries")

Morbidity and Function

"Up to 50% of patients will require surgery" during the index hospitalization
Neurologic complications occur in 15–30% of cases, "up to 60% of patients experience neurological complications" when vegetations exceed 30mm
Acute valvular incompetence develops in approximately one-third of cases; intracardiac abscesses in ~14%; AV block in ~8%
Survivors of embolic stroke or requiring valve replacement face durable functional impairment (documented in general stroke/cardiac-surgery QoL literature; IE-specific disease-specific QoL instrument data are limited)

Disease Course / Complications

Cardiac: Acute heart failure/cardiogenic shock (leading mortality predictor), paravalvular abscess, fistula, conduction abnormalities/heart block, pericarditis
Neurologic: Ischemic embolic stroke, intracranial hemorrhage (including from mycotic aneurysm rupture), brain abscess, meningitis
Renal: Immune-complex glomerulonephritis, embolic renal infarction, acute kidney injury (from sepsis, nephrotoxic antibiotics, or hemodynamic compromise)
Vascular: Septic/mycotic aneurysms (any arterial bed), splenic infarct/abscess, septic pulmonary emboli (right-sided IE)
Musculoskeletal: Septic arthritis, vertebral osteomyelitis/discitis

Prognostic Factors and Biomarkers

Dominant predictors of mortality: heart failure/hemodynamic compromise, septic shock, uncontrolled local infection/periannular complications, S. aureus etiology, negative blood cultures, and failure to undergo indicated surgery
Prognostic biomarkers: NT-proBNP (OR 14.9 for in-hospital mortality), procalcitonin, CRP (specifically associated with embolic risk), cardiac troponin (s-cTnI showed highest single-marker accuracy for mortality prediction in one multimarker study), IL-6, TNF-α, pro-adrenomedullin, copeptin

12. Treatment

Pharmacotherapy

Antibiotic selection is organism- and susceptibility-directed, with prolonged parenteral courses (NCIT:C15986 Pharmacotherapy): - Streptococcal native-valve IE (penicillin-susceptible): Ceftriaxone 2g IV daily × 4 weeks, or ceftriaxone + gentamicin (synergy regimen) × 2 weeks - MSSA native-valve IE: Nafcillin/oxacillin or cefazolin × 6 weeks - MRSA native-valve IE: Vancomycin or daptomycin × 6 weeks - Enterococcal IE: Combination therapy — ampicillin (or penicillin G) plus an aminoglycoside (gentamicin) × 4–6 weeks (increasingly, ampicillin plus ceftriaxone dual beta-lactam regimens to reduce aminoglycoside nephrotoxicity) - Prosthetic-valve IE: Minimum 6 weeks, combination therapy typically including rifampin plus gentamicin (staphylococcal PVE) to address biofilm-associated organisms - Fungal (Candida) IE: Echinocandins (e.g., caspofungin, micafungin) or liposomal amphotericin B ± flucytosine as first-line, with fluconazole step-down; "no difference in either 42-day or 1-year mortality between those receiving an amphotericin B-based regimen vs those receiving an echinocandin-based regimen," and echinocandins are increasingly favored for their renal safety profile - Culture-negative/atypical organisms: Doxycycline ± hydroxychloroquine for chronic Coxiella burnetii (Q fever) endocarditis (often prolonged, sometimes lifelong, therapy); doxycycline-based regimens for Bartonella

Pharmacogenomics: Not a major axis of IE-specific precision therapy at present (unlike oncology); relevant PGx considerations are largely generic antibiotic-safety pharmacogenomics (e.g., vancomycin nephrotoxicity monitoring, aminoglycoside ototoxicity risk) rather than IE-specific gene-drug pairs in CPIC/PharmGKB.

Surgical and Interventional

Standard surgical indications (NCIT:C15329 Surgical Procedure / NCIT:C16186 Orthopedic-analog cardiac procedure term / more precisely valve-specific procedure terms): severe heart failure from valve dysfunction, uncontrolled infection (periannular abscess, persistent bacteremia despite appropriate antibiotics, fungal/highly resistant organisms), prosthetic-valve infection, invasion beyond the leaflets (abscess/fistula/pseudoaneurysm), recurrent systemic embolization despite antibiotics, and large mobile vegetations (classically >10mm with embolic events)
Emergency surgery (<24 hours) for cardiogenic shock; urgent surgery (within days) for progressive heart failure or uncontrolled infection
Valve repair preferred over replacement when feasible, especially mitral/tricuspid; allograft favored for aortic valve in the setting of annular abscess; choice between mechanical and bioprosthetic valve follows standard non-IE-specific criteria (PMID:31832353, AATS 2016 consensus guidelines)

Supportive and Rehabilitative Care

Hemodynamic support and management of septic shock/heart failure during acute treatment; anticoagulation management is individualized (embolic risk vs. hemorrhagic transformation risk, particularly in mechanical-valve patients with concurrent stroke)
Post-surgical cardiac rehabilitation and, where indicated, post-stroke rehabilitation (physical/occupational/speech therapy)

Experimental / Investigational

Bacteriophage therapy for refractory/multidrug-resistant staphylococcal or Gram-negative IE (case-report-level evidence, active investigational area)
Novel anti-biofilm and anti-adhesin (anti-MSCRAMM) therapeutic strategies targeting FnBPA/ClfA remain preclinical
Search of ClinicalTrials.gov identified ongoing interventional and observational trials (e.g., NCT06403839, evaluating preoperative dental screening to reduce IE risk in surgical valve-replacement patients)

Treatment Strategy

Treatment algorithms follow society guidelines (AHA/ACC and, more comprehensively and recently, ESC 2023): empiric broad-spectrum therapy pending cultures → organism-directed narrow-spectrum regimen once identified → reassessment for surgical indications throughout the antibiotic course, ideally via a multidisciplinary "Endocarditis Team" (cardiology, cardiac surgery, infectious disease, microbiology, sometimes neurology) — an ESC-endorsed structural recommendation
Two-phase inpatient/outpatient model: "the first phase of antibiotic treatment consists of 2 weeks of in-hospital parenteral treatment," during which surgery (if indicated) is performed, followed by completion of therapy (sometimes via outpatient parenteral antibiotic therapy, OPAT, for stable patients)

For each treatment class, suggested NCIT terms: NCIT:C15986 (Pharmacotherapy), NCIT:C15632 (Chemotherapy — n/a here), NCIT:C15329 (Surgical Procedure), NCIT:C15289 (Organ/valve replacement — Organ Transplantation is the closest existing generic NCIT class for valve replacement framing), NCIT:C15747 (Supportive Care), NCIT:C15315 (Rehabilitation).

13. Prevention

Prevention Levels

Primary prevention: Antibiotic prophylaxis before invasive dental procedures in defined high-risk patients (see below); good oral hygiene and routine dental care for all patients with predisposing cardiac lesions; harm-reduction interventions for people who inject drugs (sterile equipment, treatment for substance use disorder) to reduce inoculation events; prompt, adequate treatment of S. aureus bacteremia from any source to prevent secondary valve seeding; meticulous aseptic technique for prosthetic valve/CIED implantation and catheter care
Secondary prevention: Early recognition and treatment of bacteremia in high-risk patients; surveillance echocardiography in patients with recurrent bacteremia or known device infection risk
Tertiary prevention: Prompt surgical intervention when indicated to prevent progression to heart failure/embolic catastrophe; long-term follow-up echocardiography after treated IE to detect relapse or valve dysfunction

Prophylaxis — High-Risk Cardiac Conditions

Per AHA (2007 guideline, reaffirmed with no substantive changes by a 2021 AHA scientific statement) and the more recently strengthened 2023 ESC guidance (elevating dental antibiotic prophylaxis in high-risk patients to a Class I recommendation): prophylaxis is recommended only for patients with the highest-risk underlying cardiac conditions: - Prosthetic cardiac valve or prosthetic material used for valve repair - Previous history of infective endocarditis - Unrepaired cyanotic congenital heart disease, or repaired congenital heart disease with residual defects at or adjacent to a prosthetic patch/device, or during the first 6 months after complete repair with prosthetic material - Cardiac transplant recipients who develop valvulopathy - (Notably, common lesions such as isolated mitral valve prolapse or bicuspid aortic valve without other high-risk features are not indications for prophylaxis under current AHA guidance, though some literature notes ongoing debate about extending coverage to BAV/MVP patients)

Regimen: Prophylaxis is reasonable for dental procedures involving manipulation of gingival tissue, the periapical region of teeth, or perforation of the oral mucosa; amoxicillin is first-line (single oral dose ~30–60 minutes before the procedure), with clindamycin, azithromycin, or cephalosporins as penicillin-allergic alternatives.

Screening/Genetic Counseling

Not applicable in the Mendelian sense; the closest analog is structural-cardiac-lesion screening (echocardiographic identification of bicuspid aortic valve, MVP) which informs prophylaxis eligibility and long-term surveillance rather than reproductive genetic counseling.

Public Health / Immunization

No licensed vaccine exists against the principal IE pathogens (S. aureus vaccine candidates have repeatedly failed in clinical trials); broader public-health measures include rheumatic-fever prevention programs (penicillin prophylaxis for rheumatic heart disease, reducing a major historical predisposing lesion in low/middle-income countries), harm-reduction services for injection drug use, and infection-control programs targeting healthcare-associated bacteremia (central-line-associated bloodstream infection [CLABSI] prevention bundles, dialysis-access care protocols).

14. Other Species / Natural Disease

Taxonomy of affected species: Domestic dogs (Canis lupus familiaris, NCBITaxon:9615) and cats (Felis catus, NCBITaxon:9685) both develop naturally occurring infective endocarditis, though it is uncommon; also described in horses and other domestic/companion animals.
Natural disease in companion animals: In dogs, "endocarditis infrequently occurs in small animals and is most often caused by bacterial infections," predominantly affecting the aortic and mitral valves. A UK retrospective series of 77 canine cases (2009–2019, PMC10099803/PMC10099803, J Small Anim Pract) and a separate 71-patient retrospective cohort documented a canine mortality rate of ~56%, with only about half of affected dogs surviving beyond two weeks. Common canine pathogens include Staphylococcus spp. (~27.5%, the most common isolate in one series), Streptococcus spp., Escherichia coli, and Bartonella spp. Complications mirror the human disease: left-sided congestive heart failure, arrhythmias, thromboembolic disease, immune-complex glomerulonephritis, and polyarthritis. Case reports also document unusual canine pathogens including Erysipelothrix rhusiopathiae and Bacillus amyloliquefaciens.
Veterinary relevance: IE is recognized as an important, high-mortality cardiac disease in veterinary internal medicine, generally underdiagnosed antemortem due to nonspecific presentation (fever, lethargy, lameness from immune-complex arthritis) preceding overt cardiac signs.
Comparative pathology: The fundamental NBTE-then-bacterial-seeding pathogenic sequence appears conserved across mammals, supporting the validity of large-animal (rabbit) and rodent (rat) models for translational study (see §15).
Zoonotic potential: Indirect — Bartonella henselae (cat-scratch disease agent) can cause IE in humans following exposure to cats, and Coxiella burnetii (Q fever), whose reservoir is livestock (sheep, goats, cattle) and their birth products, is a major zoonotic cause of human culture-negative IE; there is no evidence of direct dog-to-human or human-to-animal IE transmission — the shared risk is a common bacterial reservoir/exposure route rather than cross-species transmission of the disease itself.

15. Model Organisms

Model Types and Systems

The dominant experimental models of IE are surgically induced, catheter-based vegetation models in mammals, not spontaneous genetic models, because IE is fundamentally an infectious rather than a genetic disease:

Rabbit model: The classical and most widely used large-animal model. A polyethylene catheter is introduced (via carotid artery, into the left ventricle across the aortic valve for left-sided disease, or via jugular vein for right-sided disease) to mechanically damage the valve and induce sterile fibrin-platelet vegetations (mimicking NBTE), after which the animal is challenged intravenously with the test organism (classically S. aureus, viridans streptococci, or enterococci) to establish infective vegetations. A refined echocardiography-guided technique for creating right-sided S. aureus IE in rabbits without open surgery has been described (PMC3598207), improving reproducibility and reducing procedural morbidity. "The models described herein closely reproduced the pathogenesis and pathophysiology of right heart catheter-induced endocarditis in humans."
Rat model: Damage to the aortic valve and sterile vegetation formation is accomplished by insertion of a polyethylene catheter through the carotid artery into the left ventricle; "the rat model of endocarditis is a well-established experimental protocol which closely approximates human native-valve endocarditis," and has been used to dissect specific virulence-factor contributions (e.g., the marginal role of von Willebrand factor-binding protein and coagulase in vegetation initiation, PMC7000203).
Mouse model: A more recently developed induced S. aureus IE model exists, enabling use of the extensive mouse genetic/immunologic toolkit; MRI has been used to visualize S. aureus-induced vegetations non-invasively in mice (PMC4167704), and a dedicated induced-mouse-IE model paper describes its development and characterization (PMID referenced via ResearchGate summary of "Development of a mouse model of induced Staphylococcus aureus infective endocarditis").
In vitro/ex vivo systems: Heterologous expression systems (e.g., Lactococcus lactis expressing individual staphylococcal MSCRAMMs such as ClfA or FnbA) are used to isolate the contribution of single adhesins to colonization/invasiveness without the confounding of the full S. aureus virulence repertoire — an important reductionist in vitro/cellular model complementing the whole-animal catheter models.

Genetic Models

Because IE pathogenesis depends jointly on host vascular anatomy/hemodynamics and pathogen virulence factors, genetic manipulation is applied predominantly to the pathogen side (isogenic S. aureus mutants lacking specific MSCRAMMs — ClfA, FnBPA/B, sortase A — to test necessity/sufficiency for vegetation colonization) rather than to host germline engineering; host-side genetic models (e.g., TLR2-knockout mice) have been used in related cardiovascular-infection/sepsis contexts and are a logical extension for testing the innate-immune susceptibility genes identified in human association studies (§4), though a comprehensive host-genetic (knockout/transgenic) IE model survey was not surfaced in this search and represents a plausible research gap or an area needing more targeted follow-up querying of MGI/IMPC resources.

Model Characteristics

Phenotype recapitulation: Catheter-induced rabbit and rat models faithfully reproduce the two-step NBTE-then-bacterial-seeding pathogenesis, valve destruction, and (in some variants) systemic embolic phenomena seen in human disease, making them the field standard for testing novel antimicrobials, anti-adhesin therapeutics, and vaccine candidates.
Model limitations: These models require mechanical/surgical induction of the initiating endothelial injury rather than arising from spontaneous structural valve disease (e.g., naturally aging bicuspid valve degeneration), so they may not fully capture the chronic, degenerative-valve-driven pathogenesis increasingly dominant in elderly human IE; they also typically model a single high-inoculum bacteremic challenge rather than the repeated, lower-grade bacteremic exposures (e.g., from dental brushing) thought to seed some human cases.

Applications

These models are used to: (1) define the molecular determinants of bacterial adherence and vegetation colonization (MSCRAMM/sortase A studies); (2) evaluate novel and combination antimicrobial regimens for efficacy in sterilizing vegetations (a setting where poor antibiotic penetration into biofilm-protected vegetations is a central pharmacologic challenge); (3) test candidate anti-virulence or vaccine strategies; and (4) develop and validate non-invasive imaging approaches (e.g., MRI vegetation visualization) for translational diagnostic research.

Resources

Model-organism databases relevant to follow-up investigation: MGI (Mouse Genome Informatics) for any TLR2/TLR5/IL6 knockout strains relevant to host-susceptibility follow-up studies; standard rabbit/rat experimental-endocarditis protocols are documented in specialized infectious-disease methods literature (e.g., the Infection and Immunity/Antimicrobial Agents and Chemotherapy experimental-endocarditis model literature) rather than a centralized model-organism repository, reflecting the surgically-induced (not strain-distributed) nature of these models.

Summary of Suggested Ontology Term Bindings for Curation

Category	Term
Disease	MONDO:0000565 (infective endocarditis)
Causal organism example	NCBITaxon:1280 (Staphylococcus aureus); NCBITaxon:1301 (Streptococcus sanguinis, representative viridans strep); NCBITaxon:1351 (Enterococcus faecalis); NCBITaxon:777 (Coxiella burnetii); NCBITaxon:773 (Bartonella henselae)
Gene (host susceptibility)	hgnc:11848 (TLR2); hgnc:11851 (TLR5); hgnc:6018 (IL6)
Gene (predisposing structural)	hgnc:3603 (FBN1)
Cell types	CL:0000233 (platelet); CL:0000115 (endothelial cell); CL:0000235 (macrophage); CL:0000775 (neutrophil)
Biological processes	GO:0007596 (blood coagulation); GO:0006954 (inflammatory response); GO:0002250 (adaptive immune response)
Anatomical sites	UBERON:0002332 (mitral valve); UBERON:0002137 (aortic valve); UBERON:0002094 (endocardium)
Key phenotypes	HP:0001945 (fever); HP:0031264 (cardiac murmur); HP:0025230 (Roth spot); HP:0001744 (splenomegaly); HP:0000099 (glomerulonephritis); HP:0001635 (congestive heart failure); HP:0001297 (stroke)
Treatment	NCIT:C15986 (Pharmacotherapy); NCIT:C15329 (Surgical Procedure)

Note on evidence gaps: Genome-wide host-susceptibility data remain underpowered (largest reported GWAS: 67 cases/72 controls, no genome-wide-significant hits); IE-specific proteomic/metabolomic/lipidomic datasets and host-genetic (knockout) animal models were not identified in this search and should be treated as unconfirmed/absent rather than assumed present.

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Infectious Agent

Differential Diagnoses

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References & Deep Research

Deep Research

Infective Endocarditis: Comprehensive Disease Characteristics Research Report

1. Disease Information

2. Etiology

Disease Causal Factors

Risk Factors

Protective Factors

Gene-Environment Interactions

3. Phenotypes

4. Genetic/Molecular Information

5. Environmental Information

6. Mechanism / Pathophysiology

Causal Chain (Initial Trigger → Clinical Manifestation)

Cell Types and Biological Processes Involved

Molecular Profiling Data

7. Anatomical Structures Affected

8. Temporal Development

9. Inheritance and Population

Epidemiology

Genetic Etiology Parameters

Population Demographics

10. Diagnostics

Clinical Tests

Genetic Testing

Clinical Criteria — the Duke/Duke-ISCVID Criteria

Screening

11. Outcome/Prognosis

Survival and Mortality

Morbidity and Function

Disease Course / Complications

Prognostic Factors and Biomarkers

12. Treatment

Pharmacotherapy

Surgical and Interventional

Supportive and Rehabilitative Care

Experimental / Investigational

Treatment Strategy

13. Prevention

Prevention Levels

Prophylaxis — High-Risk Cardiac Conditions

Screening/Genetic Counseling

Public Health / Immunization

14. Other Species / Natural Disease

15. Model Organisms

Model Types and Systems

Genetic Models

Model Characteristics

Applications

Resources

Summary of Suggested Ontology Term Bindings for Curation

Sources