Antiplatelet Resistance in Coronary Artery Bypass Grafting: A Systematic Review

Introduction: Aspirin and clopidogrel are the most commonly used antiplatelet agents, either alone or as dual therapy, in patients undergoing CABG surgery to reduce organ ischaemia and mortality. The systematic review aims to explore the resistance to the antiplatelet agents, how to assess it, and the effect of resistance on the outcomes in CABG surgery. Materials & methods: A systematic search is carried out on MEDLINE via Ovid, PubMed, Embase, the Cochrane Library Database and Google Scholar until November 2021 to look for studies evaluating the antiplatelet resistance in patients undergoing both on-pump and off-pump CABG surgery. Only high-quality studies were included after the risk of bias assessment. Results: A total of 17 studies, of which 3 randomised controlled trials and 14 observational studies were included after inclusion criteria is applied. The incidence of aspirin resistance ranges from 11-51.5%, whereas, clopidogrel resistance is 22%. A wide variety of different assessment methods for antiplatelets are reported. Antiplatelet resistance is a predictor of vein graft occlusion, with up to 13 fold increase in occlusion rate. There is no overall effect of aspirin resistance on mortality, stroke or myocardial infarction, however, clopidogrel resistance leads to higher mortality, MI and target vessel revascularisations. The effect of cardiopulmonary bypass on antiplatelet resistance is not clear. Conclusion: There is no uniform definition of antiplatelet resistance. Assessment methods differ greatly and their results are not interchangeable. Antiplatelet resistance is associated with a higher rate of graft occlusion in CABG patients. Aspirin resistance does not influence overall adverse outcomes, however, clopidogrel resistance leads to worse outcomes.