Merck Manual

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Noninfective Endocarditis


Guy P. Armstrong

, MD, North Shore Hospital, Auckland

Last full review/revision Jul 2019| Content last modified Jul 2019
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Noninfective endocarditis (nonbacterial thrombotic endocarditis) refers to formation of sterile platelet and fibrin thrombi on cardiac valves and adjacent endocardium in response to trauma, circulating immune complexes, vasculitis, or a hypercoagulable state. Symptoms are those of systemic arterial embolism. Diagnosis is by echocardiography and negative blood cultures. Treatment consists of anticoagulants.

Endocarditis usually refers to infection of the endocardium (ie, infective endocarditis). The term can also include noninfective endocarditis, in which sterile platelet and fibrin thrombi form on cardiac valves and adjacent endocardium. Noninfective endocarditis sometimes leads to infective endocarditis. Both can result in embolization and impaired cardiac function.

The diagnosis of noninfective endocarditis is usually based on a constellation of clinical findings rather than a single definitive test result.


Vegetations are not caused by infection. They may be clinically undetectable or become a nidus for infection (leading to infective endocarditis), produce emboli, or cause valvular dysfunction.

Catheters passed through the right side of the heart may injure the tricuspid and pulmonic valves, resulting in platelet and fibrin attachment at the site of injury. In disorders such as systemic lupus erythematosus (SLE), circulating immune complexes may result in friable platelet and fibrin vegetations along a valve leaflet closure (Libman-Sacks lesions). These lesions do not usually cause significant valvular obstruction or regurgitation. Antiphospholipid antibody syndrome (lupus anticoagulants, recurrent venous thrombosis, stroke, spontaneous abortions, livedo reticularis) also can lead to sterile endocardial vegetations and systemic emboli. Rarely, granulomatosis with polyangiitis leads to noninfective endocarditis.

Marantic endocarditis

In patients with chronic wasting diseases, disseminated intravascular coagulation, mucin-producing metastatic carcinomas (eg, of lung, stomach, or pancreas), or chronic infections (eg, tuberculosis, pneumonia, osteomyelitis), large thrombotic vegetations may form on valves and produce significant emboli to the brain, kidneys, spleen, mesentery, extremities, and coronary arteries. These vegetations tend to form on congenitally abnormal cardiac valves or those damaged by rheumatic fever.

Symptoms and Signs

Vegetations themselves rarely cause symptoms unless their size and location cause valvular dysfunction, sometimes causing dyspnea and/or palpitations. Symptoms result from embolization and depend on the organ affected (eg, brain, kidneys, spleen). Fever and a heart murmur are sometimes present.


  • Blood cultures

  • Echocardiography

Noninfective endocarditis should be suspected when chronically ill patients develop symptoms suggesting arterial embolism. Serial blood cultures and echocardiography should be done. Negative blood cultures and the presence of valvular vegetations (but not atrial myxoma) suggest the diagnosis. Examination of embolic fragments after embolectomy can help make the diagnosis.

Differentiation from culture-negative infective endocarditis may be difficult but is important. An anticoagulant is often needed in noninfective endocarditis but is contraindicated in infective endocarditis. Assays for antinuclear antibodies and antiphospholipid syndrome should be done.


Prognosis is generally poor, more because of the seriousness of predisposing disorders than the cardiac lesion.


  • Anticoagulation

Treatment consists of anticoagulation with heparin (either intravenous unfractionated or subcutaneous low molecular weight). New oral anticoagulants (NOACs) and warfarin are not regarded as effective, although no comparative trials have been undertake in this rare condition.. Predisposing disorders should be treated whenever possible.

Key Points

  • Noninfective endocarditis is much less common than infective endocarditis.

  • Sterile vegetations form on heart valves in response to factors such as trauma, circulating immune complexes, vasculitis, or a hypercoagulable state.

  • The sterile vegetations can embolize or become infected but rarely impair valvular or cardiac function.

  • Evaluation is with echocardiography and exclusion of infective endocarditis using blood cultures.

  • Prognosis depends mainly on the underlying cause, which is often a serious illness.

  • Treatment is usually with anticoagulation.

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