Prevention of left ventricular mural thrombus.

Acute myocardial infarction is associated with a high incidence of left ventricular mural thrombosis, which causes most of the systemic emboli. A double-blind trial was undertaken in patients with anterior transmural myocardial infarction to evaluate the ability of a high-dose heparin regimen to prevent left ventricular mural thrombosis. The high dose consisted of 12,500 U of calcium heparin subcutaneously every 12 hours for 10 days, which was compared with a low dose consisting of 5,000 U every 12 hours. The formation of left ventricular mural thrombosis was assessed by means of 2-dimensional echocardiography on day 10 after infarction. The high-dose group had a significantly lower incidence of left ventricular mural thrombosis than did the low-dose group. This was achieved without increasing the incidence of bleeding. The benefits of high-dose heparin were associated with maintaining plasma heparin concentrations at 0.2 U/ml and activated partial thromboplastin time between 50 and 60 seconds.