Infective Endocarditis
System: Cardiovascular Infections · Parent MOC: MOC - Diseases by System
One-Sentence Definition
Infection of the endocardial surface (usually valves), diagnosed by microbiology + echocardiography (modified Duke criteria), with high risk of emboli and heart failure.
Clinical Presentation
- Fever, new/changing murmur, anemia of chronic disease
- Embolic phenomena: stroke, splenic/renal infarcts, Janeway, Osler, splinter hemorrhages
- Acute (destructive, S. aureus) vs subacute (viridans strep)
Pathogens
| Context | Organism | Notes |
|---|---|---|
| Acute, virulent | Staphylococcus aureus | Native or prosthetic; IVDU → right-sided |
| Subacute | Viridans streptococci (TBD) | Dental / oral source |
| GI/GU association | Enterococcus (TBD) | Older men, manipulation |
| Prosthetic / culture-negative | CoNS, HACEK, Coxiella, Bartonella (TBD) | Special tests |
Pathogenesis
- Endothelial injury → platelet-fibrin → microbial adherence → vegetation (Biofilm-like)
- Continuous bacteremia → always think IE in S. aureus bacteremia
Diagnosis
| Step | Test | Note |
|---|---|---|
| Micro | ≥3 blood culture sets before abx | Continuous bacteremia pattern |
| Imaging | TTE then TEE if indicated | Vegetations, regurgitation, abscess |
| Criteria | Modified Duke | Pathologic / clinical definite-possible |
| Extras | ECG (PR prolongation → abscess), dental eval |
Treatment Principles
- Prolonged IV (or selected oral step-down) bactericidal therapy guided by organism/AST
- Early surgical consult: HF, uncontrolled infection, prevention of embolism per indications
- Source: remove infected lines; dental as needed
Prevention
- Antibiotic prophylaxis only for selected high-risk cardiac conditions + specific procedures (guideline-limited)
- IVDU harm reduction; line care
Differential / Pitfalls
- Nonbacterial thrombotic endocarditis, myxoma, culture-negative IE (prior abx, fastidious organisms)
- Single positive CoNS = contaminant until proven otherwise
Learning Aids
Clinical Example
Example
Case: Fever + S. aureus in 3/3 blood cultures; new murmur.
Question: Must-not-miss workup?
Answer: Treat as Infective Endocarditis until excluded — echo (TEE if needed), metastatic focus search, source control, ID/AST-guided long therapy. See Staphylococcus aureus · Bloodstream and Sepsis.
Related
- Cardiovascular Infections · Bloodstream and Sepsis · Device-Associated Infections
- Staphylococcus aureus · MOC - Antimicrobials
Active Recall
- Why obtain multiple blood cultures before antibiotics?
- Acute vs subacute classic organisms?
- Name two surgical indications in IE.