Infective Endocarditis Overview

Study Notes

Defined as a microbial infection affecting native heart valves or prosthetic valves, or the endothelial lining of cardiac chambers or blood vessels.
Pathophysiology: Caused by bacteremia and endothelial injury, often secondary to high-velocity jets on predisposed endocardial linings (e.g., mitral regurgitation, aortic regurgitation, ventricular septal defect).
Causative organisms are typically bacteria, but may also include rickettsia, chlamydia, or fungi.
Disease presentations can be acute, subacute, or chronic.

High-grade persistent fever (greater than 5 days) not responsive to usual antibiotics, without an apparent cause.
Prominent or changing heart murmurs.
Acute heart failure.
Acute embolic events (e.g., cerebrovascular accident, acute limb ischemia).
Renal failure as a potential complication.

Major criteria: Positive blood cultures with specific organisms from two separate cultures taken 12 hours apart, or three or more positive cultures taken over 1 hour; Endocardial involvement evidenced by positive echocardiographic findings of vegetation or new valvular regurgitation.
Minor criteria: Predisposing cardiac condition or intravenous drug use; Fever (temperature ≥38°C); Embolic event; Vasculitis; Positive blood culture growth that doesn't fulfil major criteria.
Definite IE: Two major criteria, or one major criterion plus three minor criteria, or five minor criteria.
Possible IE: One major criterion and one minor criterion, or three minor criteria.
Rejected IE: Firm alternate diagnosis or resolution of IE manifestations with 4 days or less of antimicrobial therapy.

Medical Treatment: Initial empirical antibiotic therapy (e.g., penicillin + gentamicin) followed by culture-specific antibiotics. Treatment duration is 4-6 weeks, though cases like Q fever or brucellosis may last for months, requiring careful monitoring of antibiotic side effects.
Surgical Treatment: Cardiac valve replacement (e.g., mitral or aortic valve replacement) for affected valves, or surgical procedures for complications like aortic root abscess or peripheral embolectomy.