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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Endocarditis usually involves infection of the inner lining of the heart (endocardium) and/or heart valves (infective endocarditis). However, endocarditis also can occur without infection. This form is called noninfective endocarditis.

Noninfective endocarditis develops when fibrous blood clots without microorganisms (sterile vegetations) form on damaged heart valves. Damage may be due to a birth defect, rheumatic fever, or an autoimmune disorder (in which antibodies attack the heart valves). Rarely, damage results from insertion of a catheter into the heart. People most at risk include those with the following:

Noninfective endocarditis, like infective endocarditis, may cause heart valves to leak or not open normally. Arteries may become blocked if vegetations break loose (becoming emboli), travel through the bloodstream to other parts of the body, and lodge in an artery, blocking it. Sometimes blockage can have serious consequences. Blockage of an artery to the brain can cause a stroke, and blockage of an artery to the heart can cause a heart attack. Organs that are often affected include the lungs, kidneys, spleen, and brain. Emboli also often travel to the skin and back of the eye (retina).

Malfunction of the heart valves can cause heart failure. Symptoms of heart failure include cough, shortness of breath, and swelling of the legs.

Symptoms of noninfectious endocarditis occur when emboli form. The symptoms depend on what part of the body is affected.


  • Echocardiography

  • Blood cultures

Distinguishing between noninfective and infective endocarditis is difficult but important because treatment differs. Noninfective endocarditis may be diagnosed when echocardiography detects vegetations on the heart valves. Echocardiography cannot determine whether vegetations are infected. In order to detect whether microorganisms are present, blood cultures are done. If no bacteria or other microorganisms are detected by blood culture, it is more likely that the endocarditis is noninfectious. Blood tests for substances that may indicate the cause of noninfective endocarditis may be needed.


  • Treatment of underlying disease

  • Anticoagulants

Anticoagulants, such as warfarin and heparin, may be used to prevent clotting, but their benefits have not been confirmed. Any underlying disease that has contributed to the development of noninfective endocarditis should be treated.

Prognosis is generally poor, more because of the seriousness of the underlying disorder than because of the heart problem.

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