Endocarditis usually refers to infection of the endocardium (ie, infective endocarditis Infective Endocarditis Infective endocarditis is infection of the endocardium, usually with bacteria (commonly, streptococci or staphylococci) or fungi. It may cause fever, heart murmurs, petechiae, anemia, embolic... read more 
). 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.
Noninfective endocarditis is rare and the diagnosis usually made at autopsy (1 General reference Noninfective endocarditis refers to formation of sterile platelet and fibrin thrombi on cardiac valves and adjacent endocardium in response to trauma, circulating immune complexes, vasculitis... read more ). Clinical diagnosis is based on a constellation of clinical findings rather than a single definitive test result.
General reference
1. Hurrell H, Roberts-Thomson R, Prendergast BD: Non-infective endocarditis. Heart 106(13):1023–1029, 2020. doi: 10.1136/heartjnl-2019-315204
Etiology of Noninfective Endocarditis
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. Valve destruction is uncommon.
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) Systemic Lupus Erythematosus (SLE) Systemic lupus erythematosus is a chronic, multisystem, inflammatory disorder of autoimmune etiology, occurring predominantly in young women. Common manifestations may include arthralgias and... read more 
, 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 Antiphospholipid Syndrome (APS) Antiphospholipid syndrome is an autoimmune disorder characterized by venous and arterial thrombosis or pregnancy complications (eg, recurrent miscarriage) and persistent autoantibodies to phospholipid-bound... read more (lupus anticoagulants, recurrent venous thrombosis, stroke, spontaneous abortions, livedo reticularis) also can lead to sterile endocardial vegetations and systemic emboli. Rarely, granulomatosis with polyangiitis Granulomatosis with Polyangiitis (GPA) Granulomatosis with polyangiitis is characterized by necrotizing granulomatous inflammation, small- and medium-sized vessel vasculitis, and focal necrotizing glomerulonephritis, often with crescent... read more 
, HIV infection Human Immunodeficiency Virus (HIV) Infection Human immunodeficiency virus (HIV) infection results from 1 of 2 similar retroviruses (HIV-1 and HIV-2) that destroy CD4+ lymphocytes and impair cell-mediated immunity, increasing risk of certain... read more 
, or COVID-19 COVID-19 COVID-19 is a respiratory illness caused by the novel coronavirus SARS-CoV-2. Infection may be asymptomatic or have symptoms ranging from mild upper respiratory symptoms to acute respiratory... read more leads to noninfective endocarditis.
Marantic endocarditis
In patients with chronic wasting diseases, disseminated intravascular coagulation Disseminated Intravascular Coagulation (DIC) Disseminated intravascular coagulation (DIC) involves abnormal, excessive generation of thrombin and fibrin in the circulating blood. During the process, increased platelet aggregation and coagulation... read more , mucin-producing metastatic carcinomas (eg, of lung, stomach, or pancreas), or chronic infections (eg, tuberculosis Tuberculosis (TB) Tuberculosis is a chronic, progressive mycobacterial infection, often with an asymptomatic latent period following initial infection. Tuberculosis most commonly affects the lungs. Symptoms include... read more 
, pneumonia Overview of Pneumonia Pneumonia is acute inflammation of the lungs caused by infection. Initial diagnosis is usually based on chest x-ray and clinical findings. Causes, symptoms, treatment, preventive measures, and... read more , osteomyelitis Osteomyelitis Osteomyelitis is inflammation and destruction of bone caused by bacteria, mycobacteria, or fungi. Common symptoms are localized bone pain and tenderness with constitutional symptoms (in acute... read more 
), 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. Half of patients with disseminated intravascular coagulation have noninfective endocarditis, suggesting a relationship between the two conditions.
Symptoms and Signs of Noninfective Endocarditis
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, digits). Fever and a heart murmur are sometimes present.
Diagnosis of Noninfective Endocarditis
Blood cultures
Echocardiography
Noninfective endocarditis should be suspected when chronically ill patients develop symptoms suggesting arterial embolism. Serial blood cultures Culture Culture is microbial growth on or in a nutritional solid or liquid medium; increased numbers of organisms simplify identification. Culture also facilitates testing of antimicrobial susceptibility... read more and echocardiography Echocardiography This photo shows a patient having echocardiography. This image shows all 4 cardiac chambers and the tricuspid and mitral valves. Echocardiography uses ultrasound waves to produce an image of... read more 
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. Anticoagulation is often needed in noninfective endocarditis but is avoided in infective endocarditis unless there is a pre-existing requirement such as a mechanical valve. Assays for hypercoagulability, antinuclear antibodies, and antiphospholipid syndrome should be done. Brain imaging is done to help guide treatment.
Prognosis for Noninfective Endocarditis
Prognosis is generally poor, more because of the seriousness of predisposing disorders than the cardiac lesion.
Treatment of Noninfective Endocarditis
Anticoagulation
Management of the underlying condition
Unless brain imaging finds a lesion prone to hemorrhagic transformation, treatment consists of indefinite anticoagulation Anticoagulants Deep venous thrombosis (DVT) is clotting of blood in a deep vein of an extremity (usually calf or thigh) or the pelvis. DVT is the primary cause of pulmonary embolism. DVT results from conditions... read more 
with heparin (either intravenous unfractionated or subcutaneous low molecular weight). Direct oral anticoagulants (DOACs) and warfarin are not regarded as effective, although no comparative trials have been undertaken 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.
