Clopidogrel responsiveness regardless of the discontinuation date predicts increased blood loss and transfusion requirement after off-pump coronary artery bypass graft surgery

Objectives The purpose of this study was to evaluate the association of the percentage of platelet inhibitory response to clopidogrel as assessed by modified thromboelastography with bleeding and transfusion requirement after off-pump coronary artery bypass graft (OPCABG) surgery. Background Interindividual variability of clopidogrel responsiveness may influence bleeding and transfusion requirement. Methods One hundred patients who received clopidogrel within 5 days of OPCABG were prospectively enrolled. The primary end point was to compare post-operative bleeding and transfusion requirement in relation to the tertile distribution of the percentage of platelet inhibitory response to clopidogrel. Results Blood loss in the patients in the third tertile was 914 ± 264 ml compared with 623 ± 249 ml in those in the first and 683 ± 254 ml in those in the second tertiles (p = 0.001). Significantly more patients in the third tertile were transfused, and the number of units transfused was also larger. On multivariate analysis, the third tertile was associated with an 11-fold increased risk of transfusion (95% confidence interval: 2.77 to 47.30, p = 0.001). The optimal cutoff value for the transfusion requirement measured by receiver-operator characteristic curve analysis was 70% platelet inhibitory response to clopidogrel (area under the curve: 0.771; 95% confidence interval: 0.674 to 0.868; p < 0.001). Conclusions A high percentage of platelet inhibitory response to clopidogrel, regardless of the proximity of clopidogrel exposure, predicts increased blood loss and transfusion requirement after OPCABG with a cutoff value of 70% for increased risk of transfusion. These findings might implicate a potential role of modified thromboelastography in deciding the timing of OPCABG in patients who need continued clopidogrel therapy.