Infective Endocarditis
A serious bacterial infection of the heart valves that can destroy the valve and spread infected clots throughout the body.
Emergency Management: Acute cardiogenic shock from acute severe aortic/mitral regurgitation. Requires emergent cardiac surgery.
Infective Endocarditis (IE) is a life-threatening infection of the endocardial surface of the heart, most commonly affecting the cardiac valves, characterized by the formation of infected vegetations composed of platelets, fibrin, microorganisms, and inflammatory cells.
Detailed Overview
IE requires a confluence of endothelial damage (which forms a sterile platelet-fibrin thrombus) and transient bacteremia (which seeds the thrombus). Left-sided valves (mitral and aortic) are most commonly affected, except in IV drug users where the tricuspid valve is highly involved. The disease presents systemically with fever and bacteremia, and locally with valve destruction, heart failure, and embolic phenomena. Prompt diagnosis via blood cultures and echocardiography, followed by prolonged bactericidal IV antibiotics, is critical.
Epidemiology & Demographics
Incidence of 3-10 per 100,000. Male to female ratio is 2:1. Increasing incidence in healthcare-associated cases and IV drug users.
Etiological Mechanism
Primarily bacterial. Staphylococcus aureus is the most common overall (30-40%), followed by Viridans group streptococci, Enterococci, and the HACEK group.
Primary Causes
Bacterial seeding of damaged endocardium
Endothelial injury (from turbulent blood flow, catheters, or electrodes) exposes subendothelial collagen, causing deposition of a sterile platelet-fibrin thrombus (Non-Bacterial Thrombotic Endocarditis). Transient bacteremia (from dental procedures, IV drug use, or GI/GU mucosal trauma) allows bacteria to adhere to this thrombus. The bacteria proliferate inside the vegetation, protected from host immune cells. The infection destroys the valve leaflet leading to acute regurgitation and heart failure. Fragments of the vegetation can embolize systemically to the brain, spleen, kidneys, or lungs (if right-sided).
Diagnostic Criteria & Guidelines
Modified Duke Criteria. Requires 2 Major OR 1 Major + 3 Minor OR 5 Minor criteria. Major: 2 positive blood cultures with typical organisms, evidence of endocardial involvement on Echo (vegetation, abscess, new regurgitation).
Empiric IV antibiotics covering MRSA, Streptococci, and Enterococci: Vancomycin 15-20 mg/kg IV q8-12h PLUS Ceftriaxone 2g IV daily. Tailor to culture results. Treat for 4-6 weeks.
Second-Line & Adjunctive Therapy
Targeted therapy: For MSSA, Nafcillin 2g IV q4h for 6 weeks. For Viridans Strep, Penicillin G 12-18 million units/day IV for 4 weeks.
Surgical & Procedural Management
Early valve replacement surgery indicated for: Heart failure, left-sided S. aureus, paravalvular abscess, fungal IE, or large vegetations (>10mm) with prior embolization.
Patient Counseling & Advice
Explain the need for prolonged IV antibiotics, often via a PICC line at home. Emphasize importance of declaring their history of IE to all future dentists/doctors for prophylaxis.
Follow-Up & Monitoring Schedule
Repeat blood cultures every 48-72h until negative. Weekly inflammatory markers and renal function while on antibiotics. Repeat Echo before discharge to establish a new baseline.
Preventive Strategies
Antibiotic prophylaxis (Amoxicillin 2g PO 1 hour before procedure) for dental procedures ONLY in high-risk patients (prosthetic valves, prior IE, unrepaired cyanotic congenital heart disease).
In-hospital mortality is 15-20%. S. aureus and prosthetic valve endocarditis have the highest mortality rates.