Cardiac involvement in the antiphospholipid syndrome.

Antiphospholipid syndrome (APS) is a systemic autoimmune disease, associated with a hypercoagulable state and fetal loss and with other clinical manifestations including cardiac involvement. Cardiac manifestations of APS are valve abnormalities (valve thickening and vegetations), occlusive arterial disease (atherosclerosis and myocardial infarction), intracardiac emboli, ventricular dysfunction, and pulmonary hypertension. Antiphospholipid antibodies (aPLs) may have a role in the accelerated atherosclerotic arterial disease observed in APS, related to their ability to induce endothelial activation. aPLs have been incriminated in the pathogenesis of heart valve lesions in APS patients. Markers of endothelial cell activation are up-regulated with prominent deposition of aPL in heart valves, suggesting aPL deposition initiates an inflammatory process that recruits complement leading to the valve lesion. Autoantibody-mediated endothelial cell activation probably plays a role in sustaining a proadhesive, proinflammatory, and procoagulant phenotype. The heterogeneity of APS clinical manifestations is likely linked to the varied effects that aPL can induce on endothelial cells and to the different functions that endothelial cells display depending on the anatomic localization.