High prevalence of antiphospholipid antibodies in patients taking procainamide

To determine whether antiphospholipid antibodies (aPL) are more prevalent in cardiac patients taking procainamide than in a control population of similar elderly cardiac patients and to determine whether these antibodies react in an ELISA in which the primary antigen is beta 2-glycoprotein I (beta 2-GPI).aPL and antibodies to beta 2-GPI were measured in 66 patients taking procainamide from a Veterans Administration Medical Center population and a control group of 30 similar cardiac patients not taking procainamide.21% of the patients taking procainamide and no control patients were found to have moderate to high aPL. There were similar results in an assay that measured anti-beta 2-GPI in the absence of exogenous phospholipids. aPL were associated with antinuclear antibodies and antihistone antibodies but not with diabetes or clinical manifestations of drug related lupus. There was no increase in cholesterol or past thrombotic history associated with aPL, but there was a frequent history of noncardiac thrombosis in patients taking procainamide (25.7%).The predictive significance of procainamide induced aPL remains unknown but beta 2-GPI dependent aPL may be of some concern in this elderly population already at high risk for thrombosis.