OBJECTIVES: We investigated the hypothesis that biological aspirin "resistance" may often be related to noncompliance in patients undergoing coronary stenting. BACKGROUND: 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. METHODS: We prospectively investigated the occurrence of aspirin noncompliance in 136 consecutive patients undergoing coronary stenting receiving aspirin 75 mg daily. We analyzed posttreatment maximal intensity of arachidonic acid-induced platelet aggregation (AA-Ag) during hospitalization after controlled intake of aspirin and 1 month after hospital discharge. After 1 month, all "nonresponders" received controlled aspirin 75 mg and assessment of response was repeated. Aspirin nonresponse was defined by AA-Ag >30%. RESULTS: During inhospital 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 nonresponders. 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 = .0004), and 19 patients (14%) were identified as nonresponders. After controlled administration of aspirin, all but one of these nonresponders became responders and were identified as patients with noncompliance rather than biological resistance. CONCLUSION: 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 noncompliant for aspirin therapy during the first month after stenting. These results suggest a need for improved education of these patients.
OBJECTIVES: We investigated the hypothesis that biological aspirin "resistance" may often be related to noncompliance in patients undergoing coronary stenting. BACKGROUND: 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. METHODS: We prospectively investigated the occurrence of aspirin noncompliance in 136 consecutive patients undergoing coronary stenting receiving aspirin 75 mg daily. We analyzed posttreatment maximal intensity of arachidonic acid-induced platelet aggregation (AA-Ag) during hospitalization after controlled intake of aspirin and 1 month after hospital discharge. After 1 month, all "nonresponders" received controlled aspirin 75 mg and assessment of response was repeated. Aspirin nonresponse was defined by AA-Ag >30%. RESULTS: During inhospital 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 nonresponders. 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 = .0004), and 19 patients (14%) were identified as nonresponders. After controlled administration of aspirin, all but one of these nonresponders became responders and were identified as patients with noncompliance rather than biological resistance. CONCLUSION: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 noncompliant for aspirin therapy during the first month after stenting. These results suggest a need for improved education of these patients.