Infective endocarditis

Pathophysiology & Etiology - Heart's Unwanted Guests

• Key Organisms & Associations:
  • Staphylococcus aureus: Most common cause overall. Affects normal valves; high virulence. Predominant in IV drug users (tricuspid valve).
  • Viridans streptococci: Subacute cases, often after dental procedures on previously damaged valves.
  • Staphylococcus epidermidis: Associated with prosthetic valves, especially within 1 year of surgery.
  • HACEK organisms: Slow-growing, gram-negative rods.

⭐ Streptococcus gallolyticus (formerly S. bovis) bacteremia warrants a colonoscopy to screen for underlying colorectal cancer.

Clinical Features - Signs From a Sick Heart

• New or Worsening Murmur: The most common finding (~85%), typically regurgitant.
• Heart Failure: Leading cause of death. Results from acute valvular destruction (esp. aortic/mitral regurgitation).
• Conduction Abnormalities: Perivalvular abscess (esp. aortic valve) can extend into the conduction system, causing a new AV block.

⭐ Development of a new atrioventricular (AV) block in a patient with endocarditis strongly suggests an aortic root abscess, a complication with high mortality.

Diagnosis - The Duke's Decree

Definitive diagnosis requires: 2 Major, 1 Major + 3 Minor, or 5 Minor criteria.

• Major Criteria

  • Blood Cultures: Persistently positive for typical IE organisms (S. aureus, Viridans strep, S. gallolyticus, HACEK).
  • Echocardiogram: Evidence of endocardial involvement (vegetation, abscess, new valvular regurgitation).

• Minor Criteria

  • Predisposition: High-risk cardiac condition or IV drug use.
  • Fever: >38°C (100.4°F).
  • Vascular Phenomena: Janeway lesions, arterial emboli, septic pulmonary infarcts.
  • Immunologic Phenomena: Osler's nodes, Roth spots, glomerulonephritis.
  • Microbiologic Evidence: Positive blood culture not meeting major criteria.

📌 Mnemonic (Clinical Signs): FROM JANE Fever, Roth spots, Osler's nodes, Murmur, Janeway lesions, Anemia, Nail-bed (splinter) hemorrhages, Emboli.

⭐ Culture-negative endocarditis is often caused by fastidious organisms (e.g., Coxiella burnetii, Bartonella spp., HACEK group) or prior antibiotic therapy.

Management & Prophylaxis - Drugs, Surgery, & Shields

• Initial Empiric Therapy: Vancomycin + Gentamicin (or Ceftriaxone).
• Definitive Therapy: Tailor to organism & sensitivities.
  • S. aureus (MSSA): Nafcillin/Oxacillin
  • S. aureus (MRSA): Vancomycin
  • Viridans Streptococci: Penicillin G or Ceftriaxone

• Surgery Indications: Uncontrolled infection, abscess, significant heart failure (CHF), recurrent septic emboli, large vegetations (>10 mm).

• Prophylaxis: Given for high-risk cardiac conditions undergoing high-risk procedures.

  • Regimen: Amoxicillin 2g PO 30-60 min before procedure.
  • PCN Allergy: Clindamycin, Azithromycin, or Cephalexin.

⭐ The most common indication for surgery in patients with infective endocarditis is congestive heart failure secondary to valvular regurgitation.

High‑Yield Points - ⚡ Biggest Takeaways

• A new-onset murmur is the most classic clinical sign of infective endocarditis.
• Staphylococcus aureus is the most common cause, especially in IV drug users affecting the tricuspid valve.
• Streptococcus viridans typically infects previously damaged valves, often following dental procedures.
• Diagnosis relies on the Duke criteria, combining blood cultures and echocardiography.
• Key peripheral stigmata include Janeway lesions (painless), Osler nodes (painful), and Roth spots.
• Culture-negative cases suggest HACEK organisms or Coxiella burnetii.