IM1.19-20 | Infective Endocarditis in Heart Failure — Summary & Reflection

KEY TAKEAWAYS

Infective endocarditis is a life-threatening infection of the endocardial surface, most commonly the valves.

Clinical presentation:
- Acute IE (S. aureus, IVDU, healthcare-associated): fulminant, rapid valve destruction, sepsis, Janeway lesions (septic microemboli)
- Subacute IE (S. viridans, rheumatic valve disease): indolent fever, Osler's nodes (immune complex), Roth spots, clubbing
- New or changed cardiac murmur is the key auscultatory finding

Pathogenesis: Endothelial injury → NBTE → bacteraemia → bacterial adhesion → vegetation → valve destruction + embolism

Diagnosis — Modified Duke Criteria:
- Definite: 2 major OR 1 major + 3 minor OR 5 minor criteria
- Major criteria: (1) positive blood cultures (typical organisms, persistent bacteraemia), (2) echocardiographic evidence (vegetation, abscess, new regurgitation)
- Minor criteria: predisposing cardiac condition or IVDU, fever ≥38°C, vascular phenomena, immunological phenomena, non-major microbiological evidence

Blood cultures: ≥3 sets from separate peripheral sites, 10 mL each, before antibiotics; prolonged incubation for HACEK; never from central line

Echocardiography: TTE first; TOE mandatory for prosthetic valve IE, perivalvular complications, inadequate TTE

Antimicrobial therapy: 4–6 weeks of bactericidal antibiotics (penicillin/ceftriaxone for streptococcal; flucloxacillin for MSSA; vancomycin for MRSA; ampicillin ± gentamicin for enterococcal)

Surgical indications: Heart failure from valve regurgitation (most urgent), uncontrolled infection/abscess, vegetation >10 mm with embolic risk, prosthetic valve IE with complications

Complications: Stroke (15–20%), paravalvular abscess (new conduction defect on ECG = abscess until proven otherwise), septic pulmonary emboli (right-sided IE), glomerulonephritis, mycotic aneurysm

REFLECT

Infective endocarditis is a condition where clinical vigilance — specifically, the habit of listening for a new murmur in any patient with unexplained fever, and the reflex to draw blood cultures before starting antibiotics — saves lives. Reflect on the two contrasting presentations in this module: the IVDU with acute tricuspid IE (septic emboli to lungs, S. aureus, aggressive course) and the rheumatic patient with subacute mitral IE (Osler's nodes, weeks of fever, streptococcal, indolent). Both are infective endocarditis, but the tempo, organism, valve involved, embolic pattern, and treatment decisions are different in almost every dimension. When you encounter a febrile patient in your clinical years with an unexplained murmur and any of the peripheral stigmata described in this module, how will you rapidly frame the clinical question: is this acute or subacute? left-sided or right-sided? What three things will you do before anything else? Building that reflex now will make you a safer and more effective clinician.