HEPARIN-INDUCED THROMBOCYTOPENIA WITH THROMBOSIS - INCIDENCE, ANALYSIS OF RISK-FACTORS, AND CLINICAL OUTCOMES IN 108 CONSECUTIVE PATIENTS TREATED AT A SINGLE INSTITUTION

Heparin-induced thrombocytopenia with thrombosis (HITT) can lead to se rious morbidity and may be potentially fatal. We reviewed our experien ce with this entity over a 4-year period, to determine the following: 1) incidence and type of thrombosis in patients with heparin-induced t hrombocytopenia (HIT), 2) clinical consequences of thrombosis, i.e., a mputation, cerebrovascular accidents and death, 3) risk factors associ ated with development of thrombosis, and 4) impact of therapy on clini cal outcomes in patients with HITT. Between 1991-1994, 108 patients we re diagnosed to have HIT by heparin-induced platelet aggregation test. Thirty-two (29%) of these developed thrombotic complications, of whic h 20 were venous, 8 arterial, and 4 both. Five of the 32 died, 3 under went amputations, and 3 had cerebrovascular accidents. The patients wh o developed thrombotic complications, when compared to those with HIT alone, were older (68.7 +/- 11.5 vs. 63.3 +/- 16 years, P=.05), had mo re severe thrombocytopenia (platelet count 46,300 +/- 30,400/mm(3) vs. 62,500 +/- 34,400/mm(3), P=.02), and developed it earlier (6.0 +/- 2. 9 vs. 7.4 +/- 3.1 days, P=.03). Multivariate analysis showed that seve rity of thrombocytopenia and early fall in platelet count were indepen dent risk factors for development of thrombotic complications. We did not find an association between development of thrombosis and clinical events (myocardial infarction, cardiac procedures or surgery, noncard iac surgery, and sepsis) that occurred immediately prior to onset of t hrombocytopenia. Heparin was stopped in all 32 patients with HITT. Six received no additional therapy, and one received a single dose of asp irin. Three of these 7 died. The other 25 received anticoagulant or mu ltiagent therapy, with 2 deaths. The death rate was lower in those who were treated with anticoagulant or multiagent therapy (P=.05). We con clude that: 1) Thrombotic complications occur in about 29% of hospital ized patients who develop HIT. 2) Early, severe fall in platelet count in elderly patients receiving heparin appears to be associated with d evelopment of thrombotic complications. 3) Our data do not show an ass ociation between development of thrombotic complications and clinical events immediately preceding the diagnosis of HIT. 4) In addition to d iscontinuation of heparin, anticoagulant or thrombolytic therapy shoul d be considered in patients with HITT. (C) 1977 Wiley-Liss, Inc.