Detection of aspirin resistance by PFA-100: prevalence and aspirin compliance in patients with chronic stable angina.

Most acute coronary syndromes result from a platelet-rich occlusion of the coronary arteries. Antiplatelet drugs are of proven efficacy in preventing myocardial infarction, unstable angina, and stroke. However, not all patients on aspirin (ASA) benefit. We studied the phenomenon of aspirin resistance with a simple and reliable platelet function analyzer--the PFA-100. Studying 31 patients with unstable angina and 105 controls, we found aspirin resistance in 42% of patients, most of whom were shown to be compliant utilizing concomitant salicylate levels.