Endocarditis

Definition/diagnostic criteria Infective endocarditis (IE) is an infection of the endocardial surface of the heart, typically affecting the heart valves. The modified Duke criteria are widely accepted for diagnosis, combining clinical, microbiological and echocardiographic findings. Definite IE is diagnosed based on either two major criteria, one major and three minor criteria, or five minor criteria. Major criteria include positive blood cultures for typical organisms and evidence of endocardial involvement, while minor criteria encompass predisposing heart conditions, fever, vascular and immunologic phenomena, and microbiological evidence not meeting major criteria.

Epidemiology Endocarditis remains a relatively rare but serious condition. The incidence in the UK is estimated at around 6-10 cases per 100,000 person-years. The condition is more prevalent in males and the elderly, and risk factors include intravenous drug use, pre-existing heart conditions, prosthetic valves, and recent dental or surgical procedures.

Diagnosis
Clinical features: Symptoms are often non-specific, including fever, malaise and anorexia. More specific signs such as new or changed heart murmurs, petechiae, Osler’s nodes, Janeway lesions, and Roth’s spots may be present. However, their absence does not rule out the disease.

Investigations: These would be performed in secondary care after referral on the basis of clinical suspicion. Blood cultures are essential and should be taken before antibiotics are administered. Transthoracic echocardiography (TTE) is the initial imaging modality, but transoesophageal echocardiography (TEE) may be needed for better visualisation. Typical abnormalities include vegetations on valve leaflets, abscess formation,or new dehiscence of a prosthetic valve.

Treatment Treatment involves prolonged courses of intravenous antibiotics. The choice of antibiotics depends on the causative organism, which is typically streptococci, staphylococci or enterococci. The British National Formulary (BNF) recommends empirical therapy with amoxicillin and gentamicin for native valve endocarditis, and vancomycin, rifampicin and gentamicin for prosthetic valve endocarditis, before culture results are available.

Surgical intervention may be necessary in cases of heart failure, uncontrolled infection or for prevention of embolic events.

Prognosis The prognosis of endocarditis depends on several factors including the causative organism, the presence of complications and the patient’s overall health. Mortality rates can be high, particularly in cases of prosthetic valve endocarditis or when caused by Staphylococcus aureus. Early diagnosis and appropriate treatment are crucial for improving outcomes.