Comparative effectiveness of clopidogrel versus aspirin as a maintenance monotherapy 1 year after coronary artery bypass grafting

OBJECTIVES: Data on the safety and efficacy of clopidogrel (CPD) monotherapy after coronary artery bypass grafting (CABG) are limited. We compared the clinical outcomes and graft patency rates during 4 years in CABG patients who maintained CPD or aspirin after 1 year of dual antiplatelet therapy (DAPT) use. METHODS: A total of 671 patients who maintained 1-year DAPT after CABG with all grafts patent on one-year follow-up angiography and switched to single antiplatelet therapy (SAPT) using CPD (n = 272) or aspirin (n = 399) between January 2009 and December 2015 were enrolled. Propensity score matching analysis was used, and 227 pairs were matched in a 1:1 ratio. Overall mortality, cardiac mortality, and major adverse events, including all-cause mortality, acute myocardial infarction, coronary reintervention or reoperation, ischaemic stroke, and major bleeding, were compared. Graft patency was evaluated using graft angiography 5 years post-surgery. RESULTS: Overall survival and the incidence of major adverse events during the 4-year follow-up did not differ significantly between the groups when un-matched (hazard ratio [HR], 95% confidence interval [CI]=1.24, 0.71 to 2.15, P = 0.46 and HR, 95% CI = 1.22, 0.77 to 1.92, P = 0.41, respectively) or matched (HR, 95% CI = 1.05, 0.55 to 2.01, P = 0.89 and HR, 95% CI = 1.01, 0.60 to 1.73, P = 0.96, respectively). In the postoperative 5-year graft angiography, new graft occlusion was found in 3.2% and 4.7% of patients and newly occurred graft occlusion rates of distal anastomoses were 1.2% and 1.6% in the CPD and aspirin groups, respectively, and were not statistically different between the 2 groups (P = 0.39 and 0.63, respectively). Changes of antiplatelet regimen were needed in 22.8% (91 of 399) of aspirin group and in 2.2% (6 of 272) of CPD group from the initiation of SAPT (P < 0.001). CONCLUSIONS: In this series of patients undergoing CABG who received DAPT and remained stable for 1 year, SAPT maintenance with CPD or aspirin did not show any significant differences in 4-year outcomes such as all-cause mortality, major adverse events, and newly occurring graft occlusion. However, more patients taking aspirin required changes in antiplatelet regimens to other antiplatelet or anticoagulation therapies.