Objectives

The Aspirin Myocardial Infarction Study (AMIS) was a National Heart, Lung and Blood Institute-sponsored, multicenter, randomized, double-blind, and placebo-controlled trial designed to test whether the regular administration of aspirin to men and women who had experienced at least one documented myocardial infarction (MI) would result in a significant reduction in total mortality over a three-year period. Cause-specific mortality, nonfatal events, and side effects were also evaluated.

Background

There was preliminary evidence that regular administration of aspirin may be of benefit to patients with known coronary heart disease. In addition, there was considerable evidence that platelet aggregation and platelet-induced thrombosis may play a role in several clinical events associated with coronary heart disease. Aspirin can inhibit the formation of prostaglandin endoperoxides and thromboxane A, which aggregate platelets and induce vasospasm, but the clinical pharmacology of the drug is further complicated by recent findings that it also blocks the synthesis of prostacyclin, an inhibitor of platelet aggregation and a vasodilator that is produced in blood vessles. Based on the encouraging but inconclusive clinical findings and the anti-platelet properties of aspirin, the AMIS Study was initiated in 1975.

Participants

Over a 13-month period, 4,524 persons between the ages of 30 and 69 years were randomized to either 1 g of aspirin per day (2,267 persons) or placebo (2,257 persons). High levels of patient compliance to study protocol were indicated by various measures.

Conclusions

Based on AMIS results, aspirin is not recommended for routine use in patients who have survived an MI. Total mortality during the entire follow-up period was 10.8% in the aspirin group and 9.7% in the placebo group. Three-year total mortality was 9.6% in the aspirin group and 8.8% in the placebo group. The percentage of definite nonfatal MI was 8.1% in the placebo group and 6.3% in the aspirin group. Coronary incidence (coronary heart disease mortality or definite nonfatal MI) was 14.1% in the aspirin group and 14.8% in the placebo group. (JAMA 1980; 243:661-669.)

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