Infective endocarditis (IE) is infection of the endocardial surface of the heart, typically heart valves but also chordae tendineae, mural endocardium, septal defects, or intracardiac devices. Pathogenesis requires endothelial injury or abnormal flow, transient bacteremia, and microbial adherence forming a vegetation composed of fibrin, platelets, and microorganisms. Native valve IE is most often caused by Staphylococcus aureus, viridans group streptococci, enterococci, and HACEK organisms; prosthetic valve IE adds coagulase-negative staphylococci early after surgery. Right-sided IE predominantly affects intravenous drug users with tricuspid valve involvement by S. aureus.
Clinical presentation ranges from indolent illness with fever, weight loss, and fatigue to acute toxic sepsis with rapid hemodynamic deterioration. Examination findings include new or changing murmur, splinter hemorrhages, Osler nodes, Janeway lesions, Roth spots, splenomegaly, and stigmata of embolic events such as stroke, peripheral embolism, or septic pulmonary emboli. Diagnosis follows the modified Duke criteria combining major (positive blood cultures with typical organisms, echocardiographic evidence of vegetation, abscess, or new valve regurgitation) and minor criteria. Three sets of blood cultures from different sites over an hour are essential before antibiotic therapy. Transthoracic echocardiography is the initial imaging, with transesophageal echocardiography (sensitivity 90%) used for prosthetic valves, abscess, or non-diagnostic TTE. Cardiac CT and 18F-FDG PET/CT increasingly guide diagnosis in difficult cases, particularly prosthetic and device-related infections.
Treatment requires prolonged intravenous antibiotics for 4-6 weeks, tailored to organism and susceptibility: penicillin or ceftriaxone for streptococci, vancomycin or daptomycin for methicillin-resistant staphylococci, ampicillin plus gentamicin or ceftriaxone for enterococci, and combination therapy with rifampin for prosthetic valve staphylococcal infection. Cardiac surgery is indicated for heart failure due to valve dysfunction, uncontrolled infection (persistent bacteremia, abscess, large vegetation greater than 10 mm), recurrent emboli, and prosthetic valve dehiscence. Early surgery within the first week may reduce embolic events in selected patients. Multidisciplinary endocarditis teams composed of cardiology, cardiac surgery, infectious disease, microbiology, and imaging specialists improve outcomes. Mortality remains 15-30%, higher with prosthetic valves, S. aureus, and surgical complications. Antibiotic prophylaxis is reserved for high-risk patients undergoing dental procedures.