Endocarditis

Endocarditis is an infection of the endocardium, the inner lining of the heart, including the heart valves. It most commonly occurs when bacteria (or, less commonly, fungi) enter the bloodstream and colonise the endocardial surface, particularly where there is existing structural abnormality such as a damaged or prosthetic heart valve. The resulting infected deposits (vegetations) can damage valve leaflets, obstruct blood flow, and release emboli that travel to the brain, kidneys, and other organs.

Infective endocarditis (IE) may be acute (caused by aggressive organisms such as Staphylococcus aureus) or subacute (caused by less virulent organisms such as Streptococcus viridans). Risk factors include structural heart disease, prosthetic valves, previous endocarditis, intravenous drug use, and poor dental hygiene. Bacteria enter the bloodstream during dental procedures, skin procedures, or through invasive medical devices.

Diagnosis requires blood cultures (to identify the causative organism), echocardiography (to visualise vegetations and assess valve damage), and clinical assessment using the Duke criteria. Treatment involves prolonged intravenous antibiotics, typically 4 to 6 weeks. Surgery (valve repair or replacement) is required when there is severe valve destruction, refractory infection, large vegetations at high embolic risk, or heart failure caused by valvular dysfunction.

In the context of cardiac arrest, endocarditis can cause sudden cardiac collapse through several mechanisms: direct extension of infection to the conduction system, catastrophic valve destruction, or emboli blocking the coronary arteries. Survivors of cardiac arrest with valve abnormalities identified on investigation should have endocarditis excluded as a cause.