Residual platelet reactivity is preferred over platelet inhibition rate in monitoring antiplatelet efficacy: insights using thrombelastography
Although thrombelastography (TEG) has been widely implemented in the clinical setting of endovascular intervention, consensus on the optimal parameter for defining high ischemic risk patients is lacking due to the limited data about the relationship between various TEG parameters and clinical outcomes. In this article, we report a post hoc analysis of a prospective, single-center cohort study, including 447 patients with acute coronary syndrome (ACS). Arachidonic acid (AA)- or adenosine diphosphate (ADP)-induced platelet-fibrin clot strength (MA AA or MA ADP ) was indicative of the net residual platelet reactivity after the treatment with aspirin or clopidogrel, respectively. AA% or ADP% was indices of the relative platelet inhibition rate on AA or ADP pathway. We found that each parameter alone was predictive of the risk of 6-month ischemic event, even after adjusting for confounding factors. However, the association between AA% and clinical outcome disappeared when further adjusted for MA AA . Likewise, inclusion of MA ADP changed the significant relation between ADP% and clinical outcome. MA ADP  > 47.0 mm and MA AA  > 15.1 mm were identified as the optimal cutoffs by receiver operating characteristic analysis. High MA AA (HR = 3.963; 95% CI: 1.152–13.632; P  = 0.029) and high MA ADP (HR = 5.185; 95% CI: 2.228–12.062; P  < 0.001) were independent predictors when both were included in multivariable Cox regression hazards model. Interestingly, an even higher risk was found for the coexisting high MA AA and high MA ADP (HR = 7.870; 95% CI: 3.462–17.899; P  < 0.001). We conclude that when performing TEG to predict clinical efficacy, residual platelet reactivity has superiority over platelet inhibition rate as a measure of thrombotic risk in patients treated with aspirin and clopidogrel after ACS.