ANTIBODIES TO PROTHROMBIN IMPLY A RISK OF MYOCARDIAL-INFARCTION IN MIDDLE-AGED MEN

Antiphospholipid antibodies in patients with ''antiphospholipid syndro me'' may be directed at least in part against plasma phospholipid-bind ing proteins, such as beta 2-glycoprotein I or prothrombin, which are involved in the control of thrombosis and haemostasis. IgG-class antib odies against prothrombin and beta 2-glycoprotein I were measured by e nzyme-linked immunoassay in initially healthy middle-aged dyslipidaemi c men (non-high-density lipoprotein >5.2 mml/l). Serum samples had bee n drawn at entry to a 5-year coronary primary-prevention trial with ge mfibrozil from 106 subjects who experienced either a non-fatal myocard ial infarction or cardiac death during the follow-up and from 106 subj ects without coronary episodes, matched for treatment group (gemfibroz il/placebo) and geographical area. The antiprothrombin antibody level, as expressed in optical density units, was significantly higher in pa tients than in controls (0.26 +/- 0.17 versus 0.22 +/- 0.09; p<0.02). A high level of antiprothrombin antibodies (highest tertile of distrib ution) predicted a 2.5-fold increase in the risk (95% confidence inter val 1.2-5.3) of myocardial infarction or cardiac death. The distributi on of IgG-class antibodies against beta 2-glycoprotein I did not diffe r significantly between cases and controls. The joint effect of antipr othrombin antibodies and other factors associated with hypercoagulativ e state: triglyceride level, lipoprotein(a) and smoking, was multiplic ative for the risk. Antiprothrombin antibodies are a new immunological predictor of myocardial infarction and the effect of these antibodies may be mediated by hypercoagulative mechanisms.