Thromboembolic Risk (if Any) Is Short-Lived in Post-Op AF

April 06, 2018

Patients with new-onset atrial fibrillation (AF) after coronary bypass surgery are at less risk of thromboembolic events, death, and AF hospitalization than those with primary, nonvalvular AF (NVAF), suggests a new cohort study.

Indeed, thromboembolic risk after coronary artery bypass graft (CABG) surgery wasn't elevated for patients with postoperative AF (POAF) compared with those who didn't develop AF.

The findings, based on 15 years of CABG and AF patients managed at a major center in Denmark, were independent of comorbidities, stroke risk-prediction scores, and medical therapies, including postoperative oral anticoagulation (OAC).

They argue against considering post-CABG AF in the same league as primary NVAF in terms of thromboembolic risk, according to a report published March 28 in JAMA Cardiology with lead author Jawad H Butt, MD, Copenhagen University Hospital, Denmark.

The findings also argue against chronic OAC to lower the risk of stroke associated with post-CABG AF, according to David R Van Wagoner, PhD, Cleveland Clinic, Ohio, who was not part of the current study.

Post-CABG AF is not a long-term condition and so doesn't call for long-term management, he observed for | Medscape Cardiology. Most likely the arrhythmia is secondary to myocardial inflammation associated with the surgery, which is temporary.

And because revascularization may improve myocardial perfusion to a level greater than before surgery, once inflammation abates the risk of stroke is probably lower than before the surgery, Van Wagoner said.

"So there's no reason to start anticoagulation just on the basis of postoperative AF. You might want to use it transiently, or at least aspirin, in the perioperative period."

The analysis compared 2108 patients who developed first-time AF after CABG surgery with 8432 patients with NVAF unrelated to surgery; overall, their median age was 69 years and 82% were men. They had been treated at a single center from 2000 to 2015, the two groups matched in a 1-to-4 ratio by age, sex, CHA2DS2-VASc score, and year of diagnosis.

Of the patients with POAF, 8.4% initiated OAC within 30 days of discharge from the CABG hospitalization; 42.9% of the NVAF group were put on OAC.

Of patients with POAF on OAC, 78.9% were also put on antiplatelets, as were 79.7% of those not put on OAC.

The median follow-up for those with POAF and those with NVAF was 5.1 years and 3.5 years, respectively.

The risk of thromboembolic events was reduced in patients with POAF compared to those with NVAF: hazard ratio (HR), 0.67 (95% CI, 0.55 - 0.81; P < .001).

That risk on OAC compared to no OAC was reduced for patients in both groups: HR, 0.55 (95% CI, 0.32 - 0.95; P = .03) for POAF and HR, 0.59 (95% CI, 0.51 - 0.68; P < .001) for NVAF.

All-cause mortality was reduced in POAF compared with NVAF: HR, 0.55 (95% CI, 0.49 - 0.61; P < .001). 

All-cause mortality on OAC compared to no OAC was not significantly reduced in patients with POAF (HR, 1.09; 95% CI, 0.82 - 1.43; P = .56) but was in patients with NVAF (HR, 0.51; 95% CI, 0.47 - 0.55; P < .001).

The risk of recurrent AF hospitalization was significantly less for patients with POAF compared to those with NVAF: HR, 0.29 (95% CI, 0.25 - 0.34; P < .001).

The 2157 patients with POAF and another cohort of 4964 patients who underwent CABG without developing AF showed about the same risk of thromboembolic events during the follow-up: HR: 1.11 (95% CI, 0.94 - 1.32; P = .24).

Within the total group that underwent CABG, those developing AF compared to those not developing AF showed a significantly increased risk of death from any cause (HR, 1.32; 95% CI, 1.18 - 1.47; P < .001) and hospitalization for AF (HR, 2.27; 95% CI, 1.84 - 2.80; P < .001).

"It is likely that some AF following cardiac surgery is indeed transient and caused by inflammation, while in other cases, it is typical clinical AF in an at-risk individual that happens to receive a diagnosis for the first time in the postoperative setting," proposes an accompanying editorial.

"Identifying this latter group who may be at higher risk of AF recurrence and stroke is not yet possible and should be a priority," write the editorialists, led by Jeff S Healey, MD, McMaster University, Hamilton, Ontario.

Butt reported no conflicts; disclosures for the other authors are listed in the report. Van Wagoner has reported receiving research grants from the National Institutes of Health and Amgen. Healey reports receiving research grants from Bristol-Myers Squibb and Pfizer; the other editorialists had no disclosures.

JAMA Cardiol. Published online March 28, 2018. Abstract, Editorial

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