• Cardiology Clinical Trials
• Hypertensive Disease

Results from the Aspirin for Asymptomatic Atherosclerosis (AAA) study, presented by Professor Gerry Fowkes, MD, University of Edinburgh, Edinburgh, Scotland, showed no support for the routine use of aspirin for the primary prevention of vascular events in people with asymptomatic atherosclerosis.

The objective of the AAA study was to evaluate whether the routine use of low-dose (100 mg) aspirin was as effective as primary prevention of vascular events in individuals at high risk of a future event, as determined by ankle brachial index (ABI) score. The primary endpoint was a composite of initial fatal or nonfatal coronary event or stroke or revascularization. Secondary endpoints were all initial vascular events (defined as a composite of a primary endpoint event or angina, intermittent claudication, or transient ischemic attack) and all-cause mortality.

The study population consisted of 3350 men and women who were recruited from general practice registers in Scotland who had a low (≤0.95) ABI score, were free of cardiovascular disease, and were not already taking routine aspirin or warfarin. Subjects were randomly assigned to receive 100 mg enteric-coated aspirin (n=1675) or matching placebo (n=1675) and were followed for a mean of 8.2 years. The mean ABI at study entry was 0.86; mean age was 62 years, and 29% was male.

There was no difference between treatment groups for either the primary or secondary endpoints (Table 1). There was, however, an increase in major hemorrhages that required hospitalization in the aspirin group (2% of subjects in the aspirin group vs 1.2% of subjects in the placebo group; HR, 1.71; 95% CI, 0.99 to 2.97). Gastrointestinal ulcers were also more frequent in subjects who were taking aspirin (0.8% of subjects in the aspirin group vs 0.5% of subjects in the placebo group).

Commenting on the use of ABI as a screening method, Prof. Fowkes said, “Although the AAA trial was not to test screening, the results would suggest that using the ABI as a tool to screen individuals free of cardiovascular disease in the community is unlikely to be beneficial if aspirin is the intervention to be used in those found to be at higher risk. Other more potent antiplatelets might be considered, but only if increased effectiveness in avoiding ischemic events is not matched by increased bleeding.”

In his discussion of the AAA study, Professor Carlo Patrono, MD, University of Rome, Rome, Italy, compared the results with those of the Antithrombotic Trialists' collaborative meta-analysis of aspirin trials [ATT Collaboration. Lancet 2009], in which treatment with aspirin resulted in a 12% proportional reduction in serious vascular events in individuals at low to moderate risk. Prof. Patrono suggested lack of statistical power, perhaps amplified by poor compliance, as the primary cause of the null response of the AAA trial.

• © 2009 MD Conference Express