Coexisting Polymorphisms of P2Y12 and CYP2C19 Genes as a Risk Factor for Persistent Platelet Activation With Clopidogrel

BACKGROUND: Coexisting polymorphisms of the genes affecting clopiogrel resistance may influence platelet activation. METHODS AND RESULTS: In 105 patients with acute coronary syndrome (ACS) treated with percutaneous coronary intervention, platelet function was measured and registered as closure time in the test with collagen and adenosine diphosphate (CADP-CT). Patients were followed for 12 months for death or recurrent myocardial infarction (MI). Genotyping revealed 7 carriers of both the C allele of P2Y12 and A allele of CYP2C19 (group 1), 14 carriers of the T allele of P2Y12 and A allele of CYP2C19 (group 2), 17 carriers of the C allele of P2Y12 and G allele of CYP2C19 (group 3) and 67 carriers of the T allele of P2Y12 and G allele of CYP2C19 (controls). The median CADP-CT value was significantly lower in group 1 than in group 2 or 3 (p<0.01) or controls (p<0.002), but did not differ between group 2 or 3 and controls. There were 2 cardiovascular deaths and 4 MI during follow-up, and the median CADP-CT value was lower in these patients (p=0.09). CONCLUSIONS: Coexisting, rather then single, polymorphisms of different genes may be related to persistent platelet activation while on clopidogrel, which raises concern about harm in patients with ACS.