Objectives: The present trial investigated the efficacy and safety of dalteparin in the prevention of arterial thromboembolism after an acute anterior myocardial infarction (MI).
Background: Left ventricular (LV) thrombus formation is associated with increased risk of arterial embolism in patients with an acute MI. Thrombolytic and antiplatelet therapy do not prevent thrombus formation.
Methods: A total of 776 patients were enrolled in a multicenter, randomized, double-blind, placebo-controlled trial of subcutaneous dalteparin (150 IU/kg body weight every 12 h during the hospital period). Thrombolytic therapy and aspirin were administered in 91.5% and 97.6% of patients, respectively. The primary study end point was the composite of thrombus formation diagnosed by echocardiography and arterial embolism on day 9 +/- 2.
Results: Of 517 patients with echocardiographic recordings available for end point analysis, thrombus formation or embolism, or both, was found in 59 (21.9%) of 270 patients (59 with thrombus, none with embolism) in the placebo group and 35 (14.2%) of 247 patients (34 with thrombus, 1 with embolism) in the dalteparin group (p = 0.03). The risk reduction of thrombus formation associated with dalteparin treatment was 0.63 (95% confidence interval 0.43 to 0.92, p = 0.02). Analyses of all randomized patients (388 in each group) revealed no significant difference between the placebo and dalteparin groups with respect to arterial embolism (6 vs. 5 patients), reinfarction (8 vs. 6 patients) and mortality rates (23 vs. 23 patients, p = NS for all). Dalteparin was associated with an increased risk of hemorrhage: major in 11 dalteparin group patients (2.9%) verus 1 placebo group patient (0.3%, p = 0.006); minor in 52 dalteparin group patients (14.8%) versus 8 placebo group patients (1.8%, p < 0.001).
Conclusions: Dalteparin treatment significantly reduces LV thrombus formation in acute anterior MI but is associated with increased hemorrhagic risk.