Platelet drug response assay in patients undergoing off-pump coronary artery bypass grafting

OBJECTIVES: We observed antiplatelet drug response before and after off-pump coronary artery bypass grafting (OPCAB) and elucidated the clinical usefulness of the platelet drug response assay (PDRA). METHODS: This retrospective observational study was conducted by including patients who underwent isolated OPCAB at our institution between December 2021 and December 2023. PDRA was performed using a turbidimetric whole-blood assay according to measure aspirin reaction unit (ARU, threshold value for responsiveness = 550) and P2Y12 reaction unit (PRU, threshold = 208). The primary end-point of this study was the change in PDRA values for aspirin and clopidogrel before and after OPCAB. The secondary end-point was early clinical outcomes and perioperative bleeding according to preoperative aspirin responsiveness. RESULTS: PDRAs were performed before and after surgery for aspirin and clopidogrel in 255 and 219 patients, respectively. The mean ARU was higher in the postoperative period than in the preoperative period [474.8 ARU (SD 71.9) vs 441.0 ARU (SD 72.4), P < 0.001], although the proportions of aspirin responders were not significant (85.9% vs 88.2%, P = 0.50). No significant change was observed in the ratio of the platelet function suppression by clopidogrel or in the mean PRU; however, the proportion of clopidogrel responders was significantly lower in the postoperative period (58.9% vs 47.9%, P = 0.019). CONCLUSIONS: The absolute ARU value increases and the proportion of clopidogrel responders decreases in the early postoperative period after OPCAB. By contrast, changes in the proportion of aspirin responders and the absolute PRU value are not statistically significant.