Changes in Antiplatelet Drug Response and Clinical Usefulness of Antiplatelet Drug Response Assay in Patients Undergoing Off-pump Coronary Artery Bypass Grafting

C. Kim¹, Y. Kang¹, J. Kim², Y. Lee¹, S. Kim¹, S. Sohn¹, J. Choi², H. Hwang^2
1Department of Thoracic and Cardiovascular Surgery, Seoul National University Hospital, Seoul, Seoul-t'ukpyolsi ²Seoul National University Hospital, Seoul, Seoul-t'ukpyolsi

Purpose: Antiplatelet agents for coronary artery disease are known to have interindividual on-treatment response variability. This study was conducted to compare the antiplatelet drug response before and after off-pump coronary artery bypass grafting and to elucidate the clinical usefulness of antiplatelet drug response assay.

Methods: Two hundred fourteen patients (66.9±10.4 years, male=79.9%) who underwent isolated off-pump coronary artery bypass grafting between December 2021 and June 2023 were enrolled. Platelet drug response assays (PDRAs) were performed using turbidimetric whole blood assay according to pre-administrated antiplatelet drugs (aspirin, P2Y12 inhibitor or both). If the patients were on dual antiplatelet agents, preoperative PDRA was performed and the regimen was changed to single antiplatelet therapy, usually median 6 days before surgery. If patients were already on single regimen, the PDRA for single drug was performed. The single agents were continued until the day of surgery. Dual antiplatelet therapy was restarted 6 hours after surgery if not contraindicated, and postoperative PDRA was performed 7 days after surgery or on the day of discharge. Changes in PDRA values before and after surgery were evaluated and an association between preoperative PDRA values for aspirin and ischemic and bleeding complications were analyzed.

Results: In the study cohort, PDRA before and after surgery for aspirin and clopidogrel was performed in 191 and 164 patients, respectively. Mean aspirin reaction unit (ARU) was significantly higher in the postoperative period than in the preoperative period (477.5±73.5 ARU vs. 437.6±72.1 ARU, p< 0.001), but there was no significant difference in the rate of aspirin responder defined as ARU < 550 (171 of 191 patients, 89.5% vs. 160/191, 83.8%, p=0.127). However, there was no significant difference in the degree of platelet function suppression by clopidogrel (24.7±25.0% vs. 26.9±23.0%, p=0.306). There were significant differences in decline of intraoperative hematocrit and postoperative hemoglobin levels between preoperative aspirin responders and non-responders (-5.8±3.1% vs. -3.6±2.4%, p=0.002, and -3.0 ± 1.5mg/dL vs. -2.1 ± 2.2mg/dL, p=0.023, respectively). However, there were no significant differences in ischemic/bleeding complications, transfusion requirements, and other early clinical endpoints between aspirin responders and non-responders.

Conclusion: Aspirin responsiveness might decrease early after OPCAB whereas clopidogrel responsiveness maintained. Use of dual antiplatelet agents after OPCAB might be helpful to prevent ischemic complications due to drug resistance to antiplatelet agents. Further study might be needed to elucidate the association between preoperative PDRA values for aspirin and clinical outcomes.

Identify the source of the funding for this research project: No funds, grants, or other support was received.