Impaired inhibition of P2Y(12) by clopidogrel is a major determinant of cardiac death in diabetes mellitus patients treated by percutaneous coronary intervention.

OBJECTIVES: We sought to determine whether low platelet response (LR) to the P2Y(12) receptor antagonist as assessed by vasodilator-stimulated phosphoprotein flow cytometry (VASP-FCT) differentially affects outcome in patients with or without diabetes mellitus undergoing percutaneous coronary intervention.

BACKGROUND: While both DM and LR to clopidogrel are known to predict an unfavorable outcome after PCI, the deleterious effect of their association is less well established. The VASP-FCT is specific for the P2Y(12) ADP receptor pathway. In this test, platelet activation is expressed as the platelet reactivity index (PRI).

METHODS: Patients were assigned to four different groups according to the presence or not of DM (DM, NDM) and LR to clopidogrel (LR, R). LR was defined as a PRI of >61%, a threshold previously identified as the optimal cut-off value to predict cardiac death following PCI.

RESULTS: A total of 436 consecutive patients (163 DM, 273 NDM) were enrolled. The proportion of LR patients was higher in DM (47.9% vs. 35.2% p=0.011). At 9±2 months follow-up, the rates of total and cardiac mortality and possible and overall stent thrombosis were higher in DM-LR patients. Conversely, the cardiovascular outcome of DM-R patients was comparable to that of NDM (-LR or -R) patients. In DM, a multivariate analysis identified LR to clopidogrel (HR 6.09 [1.27-29.08], p=0.023) as the sole independent predictor of cardiac mortality.

CONCLUSIONS: In DM patients undergoing PCI, LR to clopidogrel is an independent predictor of cardiac death.