Infective Endocarditis

Infective endocarditis (IE) is an infection of the endocardial surface of the heart, usually involving the heart valves, caused by bacteria or fungi, leading to formation of vegetations, valve destruction, and systemic embolization.

Definition

Epidemiology

Incidence: 3–10 cases per 100,000 person-years in developed countries; higher in patients with prosthetic valves or structural heart disease
More common in males and older adults
Risk factors: pre-existing valvular disease, prosthetic heart valves, intravenous drug use, indwelling catheters, prior endocarditis
Causative organisms vary by region and patient population
High morbidity and mortality if diagnosis and treatment are delayed

Etiology

Bacterial causes: Staphylococcus aureus (most common), Streptococcus viridans, Enterococcus species
Fungal causes: Candida spp., Aspergillus spp. (less common, usually in immunocompromised patients)
Pathogens gain access to bloodstream via dental procedures, intravenous drug use, indwelling catheters, or surgery
Biofilm formation on valves and prosthetic material protects organisms from host immunity and antibiotics
Risk factors: poor dental hygiene, recent invasive procedures, immunosuppression, congenital or rheumatic heart disease

Pathophysiology

Endothelial injury promotes platelet and fibrin deposition, forming a nidus for microbial adherence
Microorganisms adhere to the damaged endocardium and form vegetations
Vegetations can destroy valve tissue and cause regurgitation
Fragments of vegetations can embolize to systemic circulation, causing infarcts or infection in other organs
Immune complex deposition may lead to renal and vascular complications
Persistent bacteremia triggers systemic inflammatory response and sepsis in severe cases