Impact of Oral Anticoagulation on Clinical Outcomes in Postoperative Atrial Fibrillation

Introduction: The impact of postoperative oral anticoagulation (OAC) with warfarin on postoperative atrial fibrillation (POAF) after coronary artery bypass grafting (CABG) was the focus of this examination of patients from the randomized endo-vein graft prospective (REGROUP) Trial.

Material and methods: REGROUP was a prospective randomized Veterans Affairs cooperative study comparing endoscopic versus open vein harvest in elective CABG patients (March 2014-April 2017) at 16 Veterans Affairs facilities. This study compared new-onset POAF patients who were treated with warfarin versus no-warfarin. Outcomes included stroke during active follow-up and a major adverse cardiac event composite of mortality, acute myocardial infarction, and repeat revascularization during active and passive follow-up.

Results: Of the 316/1103 (28.6%) of REGROUP patients who developed new-onset POAF, 45 patients were excluded - mainly for preoperative warfarin use. Of the remaining 269 patients, 85 received OAC with warfarin (OAC group); 184 did not (no-OAC group). Stroke rates during active follow-up (32 [IQR 24-38] mo) were 3.5% OAC group versus 5.4% no-OAC group (P = 0.76); major adverse cardiac eventrates were 20% OAC versus 11.4% no-OAC (P = 0.06). On longer follow-up of (median 4.61 [IQR 3.9-5.1] y), discharge OAC use was associated with all-cause mortality after adjusting for Society of Thoracic Surgeons mortality risk (20.0% versus 11.4% no-OAC use; HR = 2.00, 95% CI: 1.05-3.81, P = 0.035).

Conclusions: REGROUP patients with POAF treated with OAC had similar stroke and higher mortality rates versus no-OAC patients. Further investigation of the risk-benefit ratio of OAC in post-CABG patients and which POAF patient subgroups might derive the most benefit with anticoagulation appears warranted.