Prevalence of aspirin resistance in patients with an evolving acute myocardial infarction

Abstract

Objective To study the prevalence and importance of aspirin resistance in patients with an evolving acute myocardial infarction (AMI) by use of the Platelet Function Analyzer-100. Introduction Previous studies have demonstrated the existence of aspirin resistance, but the clinical relevance of the phenomenon remains to be clarified. If aspirin resistant patients comprise a high-risk subgroup, it might be expected that the prevalence of aspirin resistance in patients with AMI would be higher than in patients without AMI. We hypothesized that the prevalence of aspirin resistance in patients with AMI was twice the prevalence in patients without AMI. Methods We included 298 consecutive patients with known cardiovascular disease who were admitted to hospital with symptoms suggestive of an AMI. All had been taking aspirin 150 mg/day for at least 7 days prior to hospital admission. Platelet function was measured immediately at admission, and aspirin resistance was defined as a collagen/epinephrine Closure Time (CT CEPI) < 165 s. Results We found that 70 (23.5%) patients were aspirin resistant, and 70 (23.5%) patients ended up with the diagnosis of an AMI. The prevalence of aspirin resistance was significantly higher in patients with AMI as compared to patients without (36% versus 20%, OR 2.26, CI 95% 1.19–4.22, p = 0.0058). The CT CEPI measured at admission was an independent factor associated with an AMI. Conclusions Aspirin resistance is present in almost one fourth of patients admitted to hospital with symptoms suggestive of an AMI, and aspirin resistance is significantly associated with the diagnosis of a definite AMI.