Infective endocarditis

Infective endocarditis (IE) is microbial infection of the endocardial surface of the heart, typically involving native or prosthetic valves or intracardiac devices, with vegetation as the characteristic lesion.

Nearly 50% of all cases now occur in older adults. In people over 65 the incidence is around four times that of the general population, and mortality is roughly twice that of younger patients.

Reasons for the rise: a high prevalence of undiagnosed degenerative valve disease, increasing use of invasive procedures, and increasing implantation of prosthetic valves and cardiac devices.

Sex distribution: there is a male predilection overall, but the proportion of women affected rises progressively with age.

Underlying cardiac lesions in the elderly are usually degenerative — calcific aortic stenosis, mitral annular calcification, mucoid mitral valve degeneration — plus prosthetic valves and cardiac implantable electronic devices. In India and other developing countries, rheumatic valvular disease with viridans streptococci remains a major pattern.

Non-cardiac risk factors: diabetes mellitus, and gastrointestinal and genitourinary tract cancers, which predispose to bacteraemia; also haemodialysis, intravascular catheters and poor dentition.

Staphylococcus aureus is the leading pathogen overall, although its relative share decreases with age.

Enterococci and Streptococcus bovis (now S. gallolyticus) are emerging as major pathogens in the elderly, reflecting genitourinary and gastrointestinal portals of entry. Isolation of S. bovis mandates colonoscopy to look for colonic neoplasia.

Coagulase-negative staphylococci dominate prosthetic valve and device infection; culture-negative endocarditis (5–7%) is usually due to prior antibiotics or fastidious organisms (HACEK, Coxiella, Bartonella, Brucella).

Classic: fever with a new or changing regurgitant murmur, splinter haemorrhages, Osler nodes, Janeway lesions, Roth spots, splenomegaly, clubbing, microscopic haematuria.

Atypical presentation in the elderly (high-yield): fever is frequently absent or blunted; presentation may be confusion or delirium, malaise, anorexia and weight loss, falls, functional decline, unexplained anaemia, back pain from spondylodiscitis, stroke, or a heart failure exacerbation. Peripheral stigmata are less often present.

Complications: heart failure from valve destruction (the commonest indication for surgery), conduction disturbance from perivalvular abscess (a listed cause of bradycardia in Pathy's), systemic embolism including stroke and mycotic aneurysm, splenic and renal infarction, glomerulonephritis, and metastatic abscess.

Blood cultures are the cornerstone: at least three sets from separate venepuncture sites before antibiotics, with adequate volume. Serology/PCR for fastidious organisms if cultures are negative.

Echocardiography: transthoracic first, but transoesophageal echocardiography is required when TTE is negative and suspicion persists, and in all prosthetic valve and device infections. Findings: vegetation, abscess, new prosthetic dehiscence, new regurgitation.

Modified Duke criteria — definite IE = 2 major, or 1 major + 3 minor, or 5 minor. Major: typical organism in two separate blood cultures, or evidence of endocardial involvement. Minor: predisposing condition, fever ≥38 °C, vascular phenomena, immunological phenomena, and microbiological evidence not meeting a major criterion.

Supporting tests: full blood count (normocytic anaemia, leucocytosis), ESR and CRP, urinalysis, renal function, ECG (new conduction delay suggests abscess), chest radiograph, and imaging of embolic sites.

Antibiotics: prolonged, high-dose, bactericidal, intravenous therapy for 4–6 weeks, guided by culture and sensitivity, delivered with an infectious diseases and cardiology "endocarditis team". In older patients, aminoglycoside use requires renal function and drug-level monitoring, and doses of all agents must be adjusted for reduced creatinine clearance. Empirical regimens must cover staphylococci, streptococci and enterococci. Surgery is indicated for heart failure from valve dysfunction, uncontrolled infection or abscess, prosthetic valve endocarditis, and recurrent embolism with a large mobile vegetation — age alone is not a contraindication, but frailty and comorbidity strongly affect operative risk.

Prophylaxis: the AHA (Wilson 2007) withdrew routine subacute bacterial endocarditis prophylaxis for most lesions, restricting it to the highest-risk cardiac conditions undergoing specified dental procedures. Pathy's argues that because gastrointestinal and genitourinary procedures are an important source of enterococcal and S. bovis bacteraemia in the elderly, patient age should be factored into global risk assessment when deciding antibiotic prophylaxis. Good oral and dental hygiene remains the most effective preventive measure.