HEPARIN-INDUCED THROMBOCYTOPENIA: ASSOCIATION OF THROMBOTIC COMPLICATIONS WITH HEPARIN-DEPENDENT IgG ANTIBODY THAT INDUCES THROMBOXANE SYNTHESIS AND PLATELET AGGREGATION

Abstract

Eleven patients in whom thrombocytopenia developed during heparin therapy were studied. Six patients (group 1) had severe thrombocytopenia with delayed onset and five of these patients had thromboembolic complications. A serum factor which induced heparin-dependent thromboxane B 2 synthesis, 14C-serotonin release, and platelet aggregation was found in all patients in group 1. The serum factor was shown to be IgG. These findings suggest that the mechanism of the severe thrombocytopenia secondary to heparin therapy is immunological and the associated thromboembolic complications may be attributed to in-vivo activation of the platelet prostaglandin pathway and platelet aggregation induced by the heparin-dependent antibody. The five patients in group 2 had mild symptomless thrombocytopenia with early onset. In this group, the heparin-dependent antibody was not found and the mechanism of the thrombocytopenia is probably a direct action of heparin on platelets.