Comparison of Aspirin Monotherapy versus Dual Antiplatelet Therapy Following Coronary Artery Bypass Grafting

Abstract

Aspirin remains the gold standard antiplatelet regimen following coronary artery bypass grafting (CABG), however, there is growing support for dual antiplatelet therapy (DAPT). This study compares outcomes of aspirin monotherapy versus DAPT following CABG. This was a propensity-matched retrospective study from a large, multi-hospital healthcare system. It included patients who received either aspirin monotherapy or DAPT following isolated CABG between 2011 and 2018. Patients prescribed aspirin monotherapy were started on 81 mg aspirin daily, and patients on DAPT were prescribed 81 mg aspirin daily and 75 mg clopidogrel daily. Patients received alternative drug dosing or antiplatelet agents other than clopidogrel only if this was prescribed for another diagnosis or they had a preexisting contraindication. Primary outcomes included overall survival and major adverse cardiac and cerebrovascular events (MACCE), defined as a composite of death, myocardial infarction, stroke, or repeat revascularization. Kaplan-Meier analysis and the log-rank test were used to compare survival and cumulative incidence curves and Gray's test were used to compare MACCE. A total of 3,562 propensity-matched patients were included, 1,242 (34.9%) receiving aspirin monotherapy and 2,320 (65.1%) receiving DAPT. Groups were well-matched with respect to age, baseline comorbidity, indication for CABG, and completeness of revascularization. Median follow-up was 4.90 years (IQR 3.30 to 6.90 years). DAPT was associated with higher rate of postoperative transfusion (30.7% vs 25.4%, p = 0.001). Overall survival was comparable between groups (1-year aspirin 95.9% versus DAPT 97.2% and 5-years aspirin 86.3% versus DAPT 87.8%; log-rank p = 0.194). Rates of MACCE were also similar (1-year aspirin 9.4% versus DAPT 8.7% and 5-years aspirin 26.7% versus DAPT 24.7%; p = 0.798). In this propensity-matched analysis, DAPT did not confer any advantage in terms of improved survival or freedom from MACCE compared to aspirin monotherapy following isolated CABG, and was associated with a higher postoperative transfusion rate.