New-Onset AF Common But Unrecognized Early After Cardiac Surgery

Bruce Jancin

November 17, 2020

One in five patients at elevated stroke risk who underwent cardiac surgery with no history of atrial fibrillation preoperatively or at discharge developed postoperative AFib documented on a continuous cardiac rhythm monitoring device within the first 30 days after leaving the hospital in the randomized SEARCH-AF trial.

"Postoperative atrial fibrillation after cardiac surgery is not confined to the hospitalization period per se. We believe that these data should help inform on clinical practice guidelines on monitoring for postoperative atrial fibrillation in such patients," said Subodh Verma, MD, PhD, reporting the results at the virtual American Heart Association scientific sessions.

"Guidelines provide little or no direction on optimal monitoring post cardiac surgery, particularly if patients are in sinus rhythm at discharge," the surgeon noted.

SEARCH-AF was an open-label, multicenter study that included 336 patients at elevated stroke risk with an average CHA2DS2-VASc score of 4, no history of preoperative AFib, and none more than briefly with resolution during hospitalization. They were randomized to 30 days of postdischarge continuous cardiac rhythm monitoring with Medtronic's SEEQ device, to Icentia's CardioSTAT device, or to usual care, with Holter monitoring at the discretion of the treating physicians.

The primary result was a cumulative duration of AFib or atrial flutter of 6 minutes or longer during that 30-day period. This outcome occurred in 19.6% of the enhanced cardiac monitoring group and 1.7% of usual-care controls. Thus, there is an ongoing persistent occult risk of AFib that typically goes unrecognized. This 10-fold difference in the incidence of postoperative AFib translated into an absolute 17.9% between-group difference and a number-needed-to-treat of 6.

The secondary outcome of a cumulative atrial fib/flutter burden of 6 hours or more during 30 days occurred in 8.6% of the continuously monitored group and none of the controls. A cumulative AFib/flutter burden of 24 hours or greater occurred in 3.1% of the enhanced cardiac monitoring group and zero controls. These are AFib burdens that in other studies have been linked to increased risks of stroke and death, said Verma, professor of cardiovascular surgery at the University of Toronto.

"From a clinical standpoint, what this trial tells me is for my patients being discharged home tomorrow from the hospital, where they haven't had AFib and I haven't initiated anticoagulation, I have a low threshold to monitor these patients and to watch for periods of sustained unrecognized atrial fibrillation," the surgeon added.

Experts: Results Won't Change Guidelines

Discussant Ben Freedman, MBBS, PhD, noted that the U.S. Preventive Services Task Force has stated that there are insufficient data available to recommend ECG screening for AFib to prevent stroke. Before the task force can be convinced to recommend it and for payers to cover it, a number of key questions need to be answered. And the SEARCH-AF trial doesn't provide those answers, said Freedman, professor of cardiology and deputy director of the Heart Research Institute at the University of Sydney.

First off, it'll be necessary to know if the risk posed by screen-detected AFib, including postoperative AFib, is similar to that of clinical AFib. Next, it must be shown that this screen-detected postoperative AFib is actionable; that is, that a screening strategy to detect postoperative AFib arising after discharge and then treat with oral anticoagulants will actually prevent more strokes than with usual care. There are large studies underway addressing that question, including HEARTLINE, STROKESTOP, and SAFERGUARD-AF, he observed.

In an interview, Rod S. Passman, MD, who gave a state-of-the-art talk on AFib detection at the meeting and wasn't involved in SEARCH-AF, said he doesn't consider the results practice-changing.

"It's not guideline-changing because you've only shown that more intensive monitoring finds more AFib. Guideline-changing would be that finding that AFib and doing something about it impacts hard outcomes, and we don't have that data yet," said Passman, an electrophysiologist who is director of the Center for Arrhythmia Research and professor of medicine and preventive medicine at Northwestern University, Chicago.

The SEARCH-AF trial was funded by the Heart and Stroke Foundation of Canada, Bristol Myers Squibb, Pfizer, and Boehringer Ingelheim. Verma reported having received speaker's fees and/or research support from those and other pharmaceutical companies. Freedman disclosed having no financial conflicts.

This article originally appeared on MDedge.com, part of the Medscape Professional Network.

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