Surgical pathology of nonbacterial thrombotic endocarditis in 30 patients, 1985-2000

To describe the causes, complications, and histological appearance of nonbacterial thrombotic endocarditis (NBTE) in a surgical population compared with those in previously reported autopsy series.

Cases were identified by reviewing the surgical pathology reports for all cardiac valvular specimens removed at Mayo Clinic, Rochester, Minn., between 1985 and 2000. Archived microscopic slides and medical records were reviewed for each study patient.

The study group consisted of 30 patients (20 female and 10 male), with a mean age of 49 years (range, 15-89 years). Of these 30 patients, 28 had single valve involvement (19 mitral, 8 aortic, and 1 tricuspid), and 2 had involvement of both their mitral and aortic valves. An underlying immune-mediated disorder was identified in 18 patients (60%), including primary antiphospholipid syndrome (in 8), rheumatic heart disease (in 6), systemic lupus erythematosus (in 2), and rheumatoid arthritis (in 2), 15 (83%) of whom were women. Of the remaining 12 patients with no autoimmune disease, only 5 (42%) were women. No patient had metastatic malignant disease or disseminated intravascular coagulopathy. Systemic embolization was documented in 10 patients (33%), 8 of whom had cerebral involvement. Valvular vegetations were visualized by echocardiography before surgery in 8 patients and were suspected but not confirmed preoperatively in 1 patient. All vegetations consisted primarily of platelets and fibrin. The site and appearance of vegetations did not vary with the underlying disease state.

In contrast to previously reported autopsy series, NBTE in a surgical population was more commonly associated with autoimmune disorders than malignancy or disseminated intravascular coagulopathy. Women were affected twice as often as men. Systemic embolization, particularly to the brain, was prominent in both surgical and autopsy series. Vegetations had a similar appearance regardless of the specific underlying disease. An antemortem diagnosis of NBTE in a patient with no known risk factors should prompt a search not only for occult malignancy, as suggested by autopsy studies, but also for autoimmune or rheumatic diseases, particularly the antiphospholipid syndrome.