Two-dimensional echocardiographic studies were prospectively performed in 93 patients with systemic lupus erythematosus (SLE) to discover the incidence and spectrum of cardiac abnormalities and to relate these findings to the presence of high levels of anticardiolipin antibodies. Assessment of the intracardiac anatomy was also performed in an additional 12 patients who had increased anticardiolipin antibody levels but did not have SLE. Fifty patients (54%) with SLE had cardiac abnormalities, and 43 patients (46%) had normal hearts. Three categories of cardiac abnormalities were identified--valvular lesions, ranging from vegetations to valvular thickening, were found in 28%, pericardial effusion or thickening was found in 20%, and regional or global left ventricular dysfunction was found in 5%. High levels of anticardiolipin antibodies were detected in 50 patients (54%) with SLE. Of those, only 11 (22%) had an entirely normal heart, whereas the remaining 39 (78%) had at least one cardiac abnormality (valvular lesions in 20, pericardial effusion in 15, and myocardial dysfunction in five patients). In patients with SLE, the presence of abnormal intracardiac anatomy was strongly associated with increased levels of anticardiolipin antibodies (p less than 0.0001). The overall sensitivity and specificity of high levels of anticardiolipin antibodies in the prediction of cardiac abnormalities was 78% and 74%, respectively, with a positive predictive accuracy of 78% and a negative predictive accuracy of 74%. Eight of the 12 patients (67%) who had increased anticardiolipin antibodies but whose disease did not fulfill the American Rheumatism Association classification criteria for SLE had cardiac abnormalities similar to those in patients with SLE compared with only four (33%) who had normal hearts (p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)