Systemic Thrombin Generation and Activity Resistant to Low Molecular Weight Heparin Administered Prior to Streptokinase in Patients with Acute Myocardial Infarction

SummaryOne hundred patients were included in a randomized open trial to assess the systemic factor Xa (FXa) and thrombin inhibitory effect as well as the safety profile of low molecular weight heparin (LMWH) given subcutaneously in conjunction with streptokinase (SK) in patients with acute myocardial infarction (MI). The treatment was initiated prior to SK, followed by repeated injections every 12 h for 7 days, using a dose of 150 anti-Xa units per kg body weight. The control group received unfractionated heparin (UFH) 12,500 IU subcutaneously every 12 h for 7 days, initiated 4 h after start of SK infusion. All patients received acetylsalicylic acid (ASA) initiated prior to SK.Serial blood samples were collected prior to and during the first 24 h after initiation of SK infusion for determination of prothrombin fragment 1+2 (Fl+2), thrombin-antithrombin III (TAT) complexes, fibrinopeptide A (FPA) and cardiac enzymes. Bleeding complications and adverse events were carefully accounted for.Infarct characteristics, as judged by creatine kinase MB isoenzyme (CK-MB) and cardiac troponin T (cTnT), were similar in both groups of patients.A comparable transient increase in Fl+2, TAT and FPA was noted irrespective of heparin regimen. Increased anti-Xa activity in patients given LMWH prior to thrombolytic treatment had no impact on indices of systemic thrombin activation.The incidence of major bleedings was significantly higher in patients receiving LMWH as compared to patients receiving UFH. However, the occurrence of bleedings was modified after reduction of the initial LMWH dose to 100 anti-Xa units per kg body weight.In conclusion, systemic FXa- and thrombin activity following SK-infusion in patients with acute MI was uninfluenced by conjunctive LMWH treatment.