According to a post hoc analysis of the EXCEL study, atrial fibrillation (AF) develops in almost one in five patients after left main coronary artery bypass surgery and is one of the strongest predictors for subsequent stroke and death.

Three years after coronary artery bypass surgery (CABG), the adjusted risk for all-cause death was threefold higher, stroke fourfold higher, and cardiovascular death nearly fivefold higher in those with postoperative atrial fibrillation (POAF). The analysis was published in the Journal of the American College of Cardiology.

The EXCEL study compared CABG and percutaneous coronary intervention (PCI) with an everolimus-eluting stent in patients with left main coronary artery disease (CAD) and low- or intermediate-risk SYNTAX scores (≤32). As reported in 2016, the two revascularization strategies were similar for the primary composite endpoint of all-cause mortality, stroke, or myocardial infarction (MI) at 3 years.

The new analysis found that new-onset AF developed at a mean of 2.7 days after revascularization in 162 patients (8.9%). All but one episode occurred in those treated with CABG (18% vs 0.1%; P < .0001). Patients with POAF spent nearly twice as long in the hospital as those without POAF (14.3 vs 8.3 days; P < .0001), with 20 patients undergoing cardioversion.

At discharge, 85.8% of patients had reverted to normal sinus rhythm. At 30 days, however, the adjusted risk for the composite of death, MI, or stroke was higher in patients with POAF than in those without. At 3 years, POAF was independently associated with stroke (hazard ratio [HR], 4.19; 95% CI, 1.74 – 10.11), all-cause death (HR, 3.02; 95% CI, 1.60 – 5.70), and cardiovascular death (HR, 4.86; 95% CI, 2.27 – 10.44).

"This data is strong enough for patients who have a high CHADsVASC score and have developed an episode of atrial fibrillation in the post-CABG phase to highly or strongly consider long-term chronic oral anticoagulation," Stone said. "And I think these patients deserve very close surveillance and monitoring to look for recurrent atrial arrhythmias and even potentially in the future, depending on their risk of AF vs hemorrhagic events, consider either left atrial appendage occlusion or ablation." 

A Call to Arms

Of special note, none of the patients with POAF were prescribed novel oral anticoagulants at discharge, and only 10.1% were sent home with warfarin. Aspirin was near-universal in both groups.

He noted that several studies are focused on how to manage AF once it's identified but said studies looking at AF prevention are also very important. The field is awaiting larger trials after two relatively small studies, including the recently reported TNT-POAF, suggested a benefit with epicardial botulinum toxin injections. Stimulation of the vagus nerve after surgery is also being examined.

"There are prophylactic measures to perhaps decrease postop atrial fibrillation, including amiodarone or beta-blocker use, but they're not widely applied," Stone said. "So it's not obvious we're making a major impact yet, to me anyway, into postop atrial fibrillation."

On multivariable analysis, advanced age, higher body mass index, and reduced ejection fraction independently predicted AF after CABG, but the corresponding C-statistics were only 0.62, 0.53, and 0.55, respectively.

"Not knowing what the AFib status of the patients was prior to the trial is really important because the number one predictor of long-term AF is a prior history of AF," Piccini said. "If most of the signal was driven by people who had known AF before surgery, that's a very different finding than if the majority of patients that drove that mortality signal did not have AF."

Ongoing studies using continuous monitoring, such as the SEARCH-AF trial, "will hopefully provide better data on the real incidence of subacute POAF," the editorialists suggest.