Effect of early anticoagulation on the frequency of left ventricular thrombi after anterior wall acute myocardial infarction.

To determine the effect of early anticoagulation on the incidence of left ventricular thrombi complicating anterior acute myocardial infarction (AMI), 82 consecutive patients admitted within 12 hours of symptom onset and with electrocardiographic changes consistent with anterior AMI were randomly assigned to 1 of 2 treatment groups. Group 1 patients received high-dose intravenous heparin to maintain the whole blood clotting time between 15 and 20 minutes, and commenced warfarin therapy within 48 hours. Group 2 patients received low-dose subcutaneous heparin and warfarin therapy if the peak creatine kinase level was more than 1,000 U/liter. Eighteen group 2 patients received warfarin, but none had a therapeutic prothrombin ratio within 5 days. The presence and morphologic characteristics of thrombus were assessed by serial 2-dimensional echocardiography. Thirty patients were excluded because AMI was not confirmed or because of technically unsatisfactory echocardiograms, death, surgery or, in group 1 patients, inadequate anticoagulation. Thrombi were identified in 29 of 52 patients (56%): in 14 of 25 group 1 patients (56%) and 15 of 27 group 2 patients (56%). Twenty-three thrombi formed within 3 days. Thrombi were protruding rather than mural only in 3 group 2 patients. The groups did not differ in baseline characteristics or in incidence, time of appearance or morphologic characteristics of thrombus (p greater than 0.05, beta for more than 25% reduction in incidence with group 1 treatment less than 0.10). Systemic embolism occurred only in 1 group 2 patient with mural thrombus.(ABSTRACT TRUNCATED AT 250 WORDS)