A randomized comparison of intravenous heparin with oral aspirin and dipyridamole 24 hours after recombinant tissue-type plasminogen activator for acute myocardial infarction. National Heart Foundation of Australia Coronary Thrombolysis Group.

Abstract

This study addressed the need for heparin administration to be continued for more than 24 hours after coronary thrombolysis with recombinant tissue-type plasminogen activator (rt-PA). A total of 241 patients with acute myocardial infarction were treated with 100 mg rt-PA and a bolus of 5,000 units i.v. heparin followed by 1,000 units/hr i.v. heparin for 24 hours. At 24 hours, 202 patients were randomized to continue intravenous heparin therapy (n = 99) in full dosage or to discontinue heparin therapy and begin an oral antiplatelet regimen of aspirin (300 mg/day) and dipyridamole (300 mg/day) (n = 103). On prospective recording, there were no differences in the pattern of chest pain, reinfarction, or bleeding complications. Coronary angiography on cardiac catheterization at 7-10 days showed no differences in patency of the infarct-related artery. The proportion of patients with total occlusion (TIMI grade 0-1) of the infarct-related artery was 18.9% in the heparin group and 19.8% in the aspirin and dipyridamole group. In the patients with an incompletely occluded infarct-related artery, the lumen was reduced by 69 +/- 2% of normal in the heparin group and 67 +/- 2% in the aspirin and dipyridamole group. Left ventricular function assessed on cardiac catheterization and radionuclide study at day 2 and at 1 month showed no differences between the two groups. Left ventricular ejection fraction on radionuclide ventriculography at 1 month was 52.4 +/- 1.2% in the heparin group and 51.9 +/- 1.2% in the aspirin and dipyridamole group. We conclude that heparin therapy can be discontinued 24 hours after rt-PA therapy and replaced with an oral antiplatelet regimen without any adverse effects on chest pain, reinfarction, coronary patency, or left ventricular function.