Atrial Fib After Bypass Packs Long-term Deleterious Punch

Patrice Wendling

February 19, 2018

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, a post hoc analysis of the EXCEL study suggests.

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).

"It's fairly common knowledge that atrial fibrillation after bypass surgery of any sort is fairly common but in terms of how consequential it is, that's relatively unknown territory," senior author, Gregg Stone, MD, from Columbia University Medical Center in New York City, told theheart.org | Medscape Cardiology. "I think this report really sheds a light on how potentially important atrial fibrillation after bypass surgery is."

The analysis was published in the February 20 issue of 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," he added.

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.

"Management of postoperative atrial fibrillation is very controversial, and I think this paper is a call to arms that we need clinical trials to help us really figure out what is the exact best way to treat these patients," Jonathan Piccini, MD, an atrial fibrillation expert from Duke University Medical Center in Durham, North Carolina, told theheart.org | Medscape Cardiology.

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.

"If you can prevent the atrial fibrillation from occurring in the first place, that's even better than trying to figure out how to treat it once it develops," Piccini said.

In EXCEL's CABG group, preoperative amiodarone was given to 3 patients who had in-hospital POAF and 12 who did not have POAF (1.9% vs 1.7%; P = .11).

"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.

"Those are moderate at best, which means they're only somewhat helpful in deciding who is going to get atrial fibrillation," Stone said.

EXCEL excluded patients with in-hospital AF before the trial, but the authors acknowledge that AF episodes before revascularization may have been missed because the case report form did not capture AF history and systematic screening for AF was not performed. Also, it is not yet known how many patients had AF at 3 years, Stone said.

Given that rates of postoperative AF after cardiac surgery are traditionally 30% to 40%, Piccini said the finding of only 18% postoperative AF would suggest that either more patients had AF in the study than were recognized or these were relatively low-risk surgical patients.

"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."

In an editorial accompanying the analysis, Atul Verma, MD, from Southlake Regional Health Centre, Newmarket, Ontario, Canada, and colleagues write, "The true incidence of POAF in the subacute phase and beyond is not well defined and is arguably higher than we traditionally assume."

Studies have suggested a 30-day incidence of 2% to 5% after cardiac surgery, but most of these used only a single 12-lead ECG on postoperative day 30. A more recent study reported a 14% incidence within 2 weeks of discharge using 14-day recorders, but they suggest this also may be an underestimation as the monitors were patient triggered and asymptomatic AF episodes may have gone undetected.

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.

SEARCH-AF trial, co-led by two of the editorialists, is comparing AF or atrial flutter detection within 30 days of cardiac surgery using 30 days of continuous heart rhythm monitoring with Medtronic's wearable SEEQ mobile cardiac telemetry patch vs usual care. Primary completion of the study is set for December 2019.

Abbott Vascular funded the EXCEL trial. Stone's employer, Columbia University, receives royalties from Abbott Vascular. Verma reports receiving research grants from Bayer, Biosense Webster, and Medtronic and serving on the advisory boards of Bayer, Biosense Webster, and Medtronic.

Follow Patrice Wendling on Twitter: @pwendl. For more from theheart.org | Medscape Cardiology, follow us on Twitter and Facebook.

J Am Coll Cardiol. 2018;71:739-748, 749-751.  Abstract, Editorial

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