Endocarditis

Endocarditis is an inflammation of the inner layer of the heart, the endocardium, typically involving the heart valves. Other structures that may be involved include the interventricular septum, the chordae tendineae, the mural endocardium, or the surfaces of intracardiac devices.

Endocarditis is characterised by lesions known as vegetations, which are composed of masses of platelets, fibrin, microcolonies of microorganisms, and scant inflammatory cells. In subacute cases, these vegetations may also include granulomatous tissue, which can fibrose or calcify.

Classification

Endocarditis can be classified as either infective or non-infective, depending on whether a microorganism is the source of the inflammation.

Signs and Symptoms

Common signs and symptoms of endocarditis include fever, chills, sweating, malaise, weakness, anorexia, weight loss, splenomegaly, a flu-like feeling, cardiac murmur, heart failure, petechia (red spots on the skin), Osler's nodes (subcutaneous nodules on hands and feet), Janeway lesions (nodular lesions on palms and soles), and Roth's spots (retinal haemorrhages).

Infective Endocarditis

Infective endocarditis is an infection of the inner surface of the heart, usually the valves. Symptoms may include fever, small areas of bleeding into the skin, heart murmur, feeling tired, and low red blood cells. Complications may include valvular insufficiency, heart failure, stroke, and kidney failure.

Causes and Risk Factors

The cause is typically a bacterial infection and less commonly a fungal infection. Risk factors include valvular heart disease (including rheumatic disease), congenital heart disease, artificial valves, hemodialysis, intravenous drug use, and electronic pacemakers. The bacteria most commonly involved are streptococci or staphylococci.

Diagnosis

The diagnosis relies on the Duke criteria, initially described in 1994 and modified in 2000. Clinical features and microbiological examinations are the first steps to diagnose infective endocarditis. Imaging is also very important, with echocardiography being the cornerstone.

Alternative imaging modalities like computer tomography, magnetic resonance imaging, and positron emission tomography/computer tomography (PET/CT) with 2-[18F]fluorodeoxyglucose (FDG) play an increasing role in the diagnosis and management.

Treatment

Treatment generally involves intravenous antibiotics, with the choice based on blood cultures. Occasionally, heart surgery is required. Prevention is recommended in high-risk patients, such as those with previous infective endocarditis, surgical or transcatheter prosthetic valves, or untreated congenital heart disease.

The number of people affected is about 5 per 100,000 per year, with males being more affected than females. The risk of death among those infected is about 25%, but without treatment, it is almost universally fatal.

Non-infective Endocarditis

Nonbacterial thrombotic endocarditis (NBTE) is most commonly found on previously undamaged valves. Unlike infective endocarditis, the vegetations in NBTE are small, sterile, and tend to aggregate along the edges of the valve or the cusps. NBTE usually occurs during a hypercoagulable state such as system-wide bacterial infection or pregnancy.

It may also occur in patients with cancer, particularly mucinous adenocarcinoma. Typically, NBTE does not cause many problems on its own, but parts of the vegetations may break off and embolize to the heart or brain, or they may serve as a focus where bacteria can lodge, thus causing infective endocarditis.

Another form of sterile endocarditis is Libman–Sacks endocarditis, which occurs more often in patients with lupus erythematosus and is thought to be due to the deposition of immune complexes. Libman-Sacks endocarditis involves small vegetations and does not have a preferred location of deposition, potentially forming on the undersurfaces of the valves or even on the endocardium.

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Self-assessment MCQs (single best answer)

What is the primary structure affected by endocarditis?

What are the vegetations in endocarditis composed of?

Which of the following is NOT a common sign or symptom of endocarditis?

Which bacteria are most commonly involved in infective endocarditis?

What is the primary diagnostic tool for infective endocarditis?

Which of the following is NOT a risk factor for infective endocarditis?

What is the prevalence of endocarditis?

What is the main treatment for infective endocarditis?

Which form of endocarditis is more likely to occur in patients with lupus erythematosus?

In nonbacterial thrombotic endocarditis (NBTE), what is the nature of the vegetations?