CLINICAL IMPORTANCE OF THROMBOCYTOPENIA OCCURRING IN THE HOSPITAL PHASE AFTER ADMINISTRATION OF THROMBOLYTIC THERAPY FOR ACUTE MYOCARDIAL-INFARCTION

Objectives. The purpose of this study was to examine the incidence and clinical implications of thrombocytopenia that occurs in hospital aft er administration of thrombolytic therapy for acute myocardial infarct ion. Background. The use of thrombolytic therapy in patients with acut e myocardial infarction has improved mortality rates, but hemorrhage r emains a major complication. Because thrombocytopenia may be associate d with hemorrhage after thrombolytic therapy, we examined the incidenc e and clinical implications of thrombocytopenia after administration o f thrombolytic therapy for acute myocardial infarction. Methods. The p atient population comprised 1,001 patients enrolled in Phases 2, 3 and 5 of the Thrombolysis and Angioplasty in Myocardial Infarction (TAMI) trial and the urokinase trial. Patients received recombinant tissue t ype plasminogen activator, urokinase or combination therapy in various dosing schemes. All patients received heparin, aspirin and a calcium channel blocking agent. Thrombocytopenia occurring anytime after throm bolytic therapy was defined as a nadir platelet count either <100,000/ mu l or <1/2 baseline. Blood loss was quantified by a bleeding index. Multiple logistic regression was used to evaluate the independent cont ribution of thrombocytopenia in a model predicting in-hospital mortali ty. Results. Thrombocytopenia occurred in 16.4% of patients, with no d ifference among the thrombolytic regimens. Patients with thrombocytope nia had a lower median acute ejection fraction and a higher likelihood of three vessel coronary artery disease than patients without thrombo cytopenia. Patients with thrombocytopenia had more hemorrhage, a highe r in hospital mortality rate and a more complicated hospital course th an patients without thrombocytopenia, even after consideration of othe r important variables, including age, acute ejection fraction, number of diseased vessels, bypass surgery and use of intraaortic balloon cou nterpulsation. Conclusions. Thrombocytopenia after thrombolytic therap y is a common event and is associated with excess hemorrhage and morta lity. Platelet counts should be monitored daily after administration o f thrombolytic therapy because the appearance of thrombocytopenia iden tifies a subset of patients at increased risk for hemorrhage and death .