Impact of Oral Anticoagulation on Clinical Outcomes in Postoperative Atrial Fibrillation
Hossein Almassi1, Jacquelyn A. Quin2, Eileen M. Stock3, Ellen DeMatt3, Kousick Biswas3, Brack Hattler4, Elaine Tseng5, Marco A. Zenati2.
1Medical College of Wisconsin, Milwaukee, WI, USA, 2VA Boston Health Care System, Boston, MA, USA, 3Perry Point VA Medical Center, Perry Point, MD, USA, 4Rocky Mountain Regional Medical center, Aurora, CO, USA, 5San Francisco VA Medical Center, San Francisco, CA, USA.
BACKGROUND: New-onset postoperative atrial fibrillation (POAF) is the most common complication after coronary artery bypass graft (CABG) surgery. The adverse impact of POAF on postoperative clinical outcomes is well documented. The impact of postoperative oral anticoagulation such as warfarin on POAF clinical outcomes remains unclear. We examined the association between warfarin use and outcomes in CABG patients with POAF enrolled in Randomized Endo-vein Graft Prospective (REGROUP) trial.
METHODS: REGROUP was a prospective randomized study enrolling 1103 elective CABG patients to endoscopic vs. open vein harvest between March 2014-April 2017 at 16 Veterans Affairs medical centers. The primary outcome was a major adverse cardiac event (MACE) composite of all-cause mortality, myocardial infarction and repeat revascularization. For this report, patients who were treated with warfarin for new-onset POAF were compared to those who were not treated with warfarin. In addition to above MACE outcomes, cardiac mortality and stroke were compared. Data on POAF were collected prospectively.
RESULTS: POAF developed in 352/1103 (31.9%) patients of which, 51 patients were excluded for preoperative warfarin use and 2 patients for other reasons. In the remaining 299 patients, 92 received warfarin; and 207 patients did not (non-warfarin group). POAF patients were older than non-POAF patients and had higher mortality risk scores for the Veterans Affairs Surgical Quality Improvement Program and Society of Thoracic Surgery (p≤0.001 for both) however, risk profiles scores were similar between warfarin and non-warfarin groups. Over a median follow-up time of 32 months (interquartile range 24-38 months, mean 30.6 ± 10.6 months), POAF patients on warfarin had a non-significant trend towards worse MACE (p = 0.08) and significantly higher cardiac mortality and myocardial infarction rates (p=0.02 and p=0.01 respectively). Stroke rates were not significantly different between the warfarin and non-warfarin groups (p=0.48) Table 1.
CONCLUSIONS: In the REGROUP trial, the use of warfarin in patients who developed POAF was associated with higher rates of cardiac mortality and myocardial infarction while no association with stroke rate was seen. Further characterization of POAF patients who are not anticoagulated after CABG and additional research on the risk-benefit ratio of anticoagulation in this population appears warranted.
Table 1: Outcomes comparing REGROUP POAF patients treated with warfarin vs. no warfarin