Continuous monitoring finds POAF, which may or may not increase stroke risk

If one looks for atrial fibrillation, chances are excellent that one will find it—especially if the search is conducted in patients following heart surgery. But once found, is it clinically meaningful?

That is the question Subodh Verma, MD, PhD, a cardiac surgeon at St. Michael’s Hospital and the University of Toronto, and colleagues sought to answer in the SEARCH trial, which was reported as a late-breaking clinical trial at the American Heart Association’s virtual Scientific Sessions 2020.

“Early postoperative atrial fibrillation (POAF) is exceedingly common,” Verma said at an AHA press briefing. “It occurs in about 30% to 50% of patients peaking at about three to five days after index cardiac surgery. And then, supposedly declining afterwards… Our study hypothesis was that a strategy of enhanced cardiac rhythm monitoring will result in an increase in Afib and Aflutter detection, when compared to usual care within 30 days after randomization among post cardiac surgical patients without a previous history of Afib or flutter and those patients that are at high risk of stroke.”

Verma and colleagues recruited 336 post-surgery patients and randomized 163 to 30 days of 24-hour, real-time cardiac rhythm monitoring using an adhesive, patch-based monitor worn on the chest. Another 173 participants were randomized to usual care and served as the control group. All patients underwent 2 weeks of continuous cardiac rhythm monitoring 6 to 9 months after surgery.

The primary outcome measure was cumulative Afib or flutter duration of 6 minutes or longer or documentation of Afib or flutter by 12-lead ECG.

“The primary outcome occurred in 19.6% of patients in the heightened surveillance arm versus 1.7% in the usual care arm,” Verma said. Thus, “a strategy of continuous rhythm monitoring unveiled a significant persistent burden of unrecognized and potentially actionable atrial fibrillation; therefore, we can conclude that postoperative atrial fibrillation after cardiac surgery is not confined to the hospitalization phase, per se. And we believe that these data are one of the first attempts to provide cogent high-quality randomized data in this space should help inform clinical practice guidelines on monitoring of postoperative atrial fibrillation in such patients.”

But is this “clinically” significant? Ben Freedman, MD, a professor of cardiology at Sydney Medical School of the University of Sydney in Australia, was not convinced. Freedman, who served as discussant for the SEARCH trial, pointed out that published studies suggest that the stroke risk in people who develop POAF following coronary artery bypass graft surgery is “relatively small, about 1% per year over the first 3 years. Moreover, there is very little difference in the stroke risk among those who develop POAF and those who don’t.”

Freedman said it shouldn’t be surprising that monitoring detected Afib in 19.6% of the patients and pointed out that “most of the action was in the first two weeks, much less after that.”

Moreover, Freedman said the true stroke risk correlates closely with Afib duration. In the SEARCH trial “there was a wide spectrum of episode duration. And we should note that the burden, or the episode duration, particularly is very important prognostic in subclinical AF. In the SEARCH trial. Although there were 19.6% with greater than 5 minutes. Earlier studies used as a cut point for significance episodes longer than 24 hours, even then the stroke risk was only 3.1% at that duration.”

Peggy Peck, Editor-in-Chief, BreakingMED™

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