019 Aspirin Non Compliance is the Major cause of “Aspirin Resistance” in Patients undergoing Coronary Stenting

Abstract

Premature discontinuation of antiplatelet therapy has been identified as a major risk factor for stent thrombosis and prior aspirin withdrawal has been associated with poor prognosis after acute coronary syndrome. We investigated the hypothesis that biological aspirin “resistance” may often be related to non compliance in patients undergoing coronary stenting. We prospectively investigated the occurrence of aspirin non compliance in 136 consecutive patients undergoing coronary stenting receiving aspirin 75 mg daily. We analyzed post-treatment maximal intensity of arachidonic acid-induced platelet aggregation (AA-Ag) during hospitalization after controlled intake of aspirin and one month after hospital discharge. After one month, all non responders received controlled aspirin 75 mg and assessment of response was repeated. Aspirin non response was defined by AA-Ag>30%. During in-hospital period, the range of AA-Ag varied from 0 to 34% with a mean value of 7.5±10% and 4 patients (3%) were classified as non responders. One month after discharge, AA-Ag of the population was significantly higher than during the hospital phase (15.3±23 vs 7.5±10%, p=0.0004) and 19 patients (14%) were identified as non responders. After controlled administration of aspirin, all but one of these “non responders” became responders and were identified as patients with non compliance rather than biological resistance. Aspirin resistance is rare in compliant patients using methods that directly indicate the degree of platelet cyclooxygenase inhibition. More than 10% of patients receiving aspirin for coronary stenting are non compliant for aspirin therapy during the first month after stenting. These results suggest a need for improved education of these patients.