Prevalences widely differ between studies reporting on aspirin resistance .
BACKGROUND The absolute risk of recurrences among patients using aspirin for prevention of cardiovascular events remains high .
Persistent platelet reactivity despite aspirin therapy might explain this in part .
Reported prevalences of this so-called aspirin resistance vary widely , between 0 % and 57 % .
OBJECTIVES The aim of the study was to systematic ally review all available evidence on prevalence of aspirin resistance and to study determinants of reported prevalence .
Relation of aspirin resistance to coronary flow reserve in patients undergoing elective percutaneous coronary intervention.
Previous studies have shown that more complete platelet inhibition improves the coronary flow reserve ( CFR ) , a measure of microvascular integrity , in patients undergoing percutaneous coronary intervention ( PCI ) . We hypothesized that patients with aspirin resistance would have impaired CFR after elective PCI . We used VerifyNow Aspirin to determine the response to aspirin in 117 consecutive patients who underwent elective single-lesion PCI . The assay results are expressed quantitatively in Aspirin Reaction Units based on the degree of platelet aggregation . All patients received a 300-mg loading dose of clopidogrel > 12 hours before and a 75-mg maintenance dose the morning of PCI . CFR was estimated using the Thrombolysis In Myocardial Infa rct ion frame count method . Of the 117 patients , 22 ( 18.8 % ) were aspirin resistant . The clinical , angiographic , and procedural characteristics of the aspirin-sensitive and -resistant patients were balanced . All patients underwent successful PCI with < 50 % residual diameter stenosis and Thrombolysis In Myocardial Infa rct ion grade 3 flow after PCI . Aspirin-resistant patients had a lower CFR than the aspirin-sensitive patients ( 1.42 + /- 0.35 vs 1.80 + /- 0.64 , p = 0.018 ) . Univariate correlates of CFR included the Aspirin Reaction Unit ( r = -0.227 , p = 0.014 ) and post-PCI creatine kinase-MB elevation ( p = 0.048 ) . Multivariate linear regression analysis revealed the Aspirin Reaction Unit to be the only independent determinant of CFR after PCI ( r2 = 0.051 , p = 0.014 ) . Thus , aspirin resistance was associated with impaired CFR in patients who underwent elective PCI , implicating insufficient aspirin-induced platelet inhibition as a cause of microvascular dysfunction by distal atherothrombotic embolization and /or spasm
Prevalences widely differ between studies reporting on aspirin resistance .
BACKGROUND The absolute risk of recurrences among patients using aspirin for prevention of cardiovascular events remains high .
Persistent platelet reactivity despite aspirin therapy might explain this in part .
Reported prevalences of this so-called aspirin resistance vary widely , between 0 % and 57 % .
OBJECTIVES The aim of the study was to systematic ally review all available evidence on prevalence of aspirin resistance and to study determinants of reported prevalence .