Impact of aspirin according to type of stable coronary artery disease: Insights from a large international cohort

BACKGROUND: Aspirin is recommended in stable coronary artery disease based on myocardial infarction and stroke studies. However, benefit among stable coronary artery disease patients who have not suffered an acute ischemic event is uncertain. The objective of this study was to evaluate the impact of aspirin in stable coronary artery disease. We hypothesized that aspirin's benefit would be attenuated among individuals with stable coronary artery disease but no prior ischemic event. METHODS: An observational study was conducted from the INternational VErapamil-SR/Trandolapril STudy cohort. Ambulatory patients ≥50 years of age with clinically stable coronary artery disease requiring antihypertensive drug therapy (n = 22,576) were classified "ischemic" if they had a history of unstable angina, myocardial infarction, transient ischemic attack, or stroke at the baseline visit. All others were classified "non-ischemic." Aspirin use was updated at each clinic visit and considered as a time-varying covariate in a Cox regression model. The primary outcome was first occurrence of all-cause mortality, myocardial infarction, or stroke. RESULTS: At baseline, 56.7% of all participants used aspirin, which increased to 69.3% at study close out. Among the "non-ischemic" group (n = 13,091), aspirin was not associated with a reduction in risk (hazard ratio [HR] 1.11; 95% confidence interval [CI], 0.97-1.28; P =.13); however, among the "ischemic" group (n = 9485), aspirin was associated with a reduction in risk (HR 0.87; 95% CI, 0.77-0.99; P =.033). CONCLUSIONS: In patients with stable coronary artery disease and hypertension, aspirin use was associated with reduced risk for adverse cardiovascular outcomes among those with prior ischemic events. Among patients with no prior ischemic events, aspirin use was not associated with a reduction in risk.