HEPARIN-INDUCED THROMBOCYTOPENIA AND THROMBOSIS - A PROSPECTIVE ANALYSIS OF THE INCIDENCE IN PATIENTS WITH HEART AND CEREBROVASCULAR DISEASES

Heparin-induced thrombocytopenia and/or thrombosis (HITT) are serious complications of heparin treatment. The incidence, as previously repor ted, varies widely and, in consequence, is not precisely known. Moreov er, most reports only concern clinically defined heparin-induced throm bocytopenia. Therefore we carried out a prospective study of the incid ence of serologically confirmed HITT. All patients admitted to the Dep artments of Cardiology and Neurology of our institution with an indica tion for treatment with therapeutic-dose intravenous unfractionated he parin were enrolled in the study. The patients were examined daily for the occurrence of thromboembolic complications. Regular platelet coun ts and tests for the presence of heparin-dependent antibodies were car ried out using two different tests: a quantitative platelet factor 4/c ount from normal values of > 120 x 10(9)/l to < 60 x 10(9)/l or to < 1 00 x 10(9)/l if there was a rapid fall of >50% of starting value or >3 0% with concomitant acute thrombosis. The observed incidence of HITT w as 1/358 patients (0.3%, 95% confidence limits 0.01-1.5%). However, El isa PF4/hep specific IgG antibodies were demonstrated in nine (2.5%) a nd IgM antibodies in seven (2.0%) of 358 patients. 30/358 patients (8. 4%) had platelet activating antibodies in the HIPAA. We conclude that the incidence of serologically confirmed HITT in this study is very lo w (0.3%) in patients with cardiac and neurologic diseases treated with intravenous unfractionated heparin. The frequency of heparin-dependen t antibodies without concomitant occurrence of thrombocytopenia is muc h higher.