Drug-eluting stent (DES)
thrombosis has a multifactorial etiology. Variable responsiveness to antiplatelet
therapy likely contributes to its pathogenesis. We aimed to determine whether patients who had experienced DES
thrombosis compared with a cohort of patients who had not would exhibit greater platelet reactivity and a greater prevalence of
aspirin and
clopidogrel resistance. The effect of
aspirin and
clopidogrel on platelet reactivity was determined after angiographically proven DES
thrombosis in 26 patients and in 21 patients who had not experienced
stent thrombosis (ST) > or =18 months after DES implantation.
Aspirin effect was assessed using the VerifyNow
Aspirin Assay, and the effect of
clopidogrel was assessed using the VerifyNow P2Y12 Assay and
vasodilator-stimulated phosphoprotein phosphorylation (VASP-P).
Aspirin resistance was present in 23% of patients with ST and 5% of controls (p = NS).
Clopidogrel resistance was present in 40% of patients with ST and 14% of controls using the P2Y12 assay (p = 0.02) and 90% of patients with ST and 67% of controls using the VASP-P assay (p = NS). Mean
aspirin reaction units were significantly greater among all patients with ST and those with early ST compared with controls (477 +/- 89 vs 429 +/- 58, p = 0.04; and 485 +/- 84 vs 429 +/- 58, p = 0.02, respectively). Mean P2Y12 reaction units were significantly greater among patients with early ST compared with controls (265 +/- 102 vs 184 +/- 76, p = 0.01). The results of the VASP-P assay did not correlate with the presence of ST. In conclusion, patients who experienced DES
thrombosis demonstrated significantly greater rates of
clopidogrel resistance as determined by P2Y12 reaction units, but not VASP-P, compared with patients without DES
thrombosis.
Aspirin reaction units were significantly greater in the DES
thrombosis population. Point-of-care testing with the VerifyNow
Aspirin and P2Y12 Assays has the potential to identify patients at increased risk of ST, particularly early ST, after DES deployment.