No Extra Drop in AF Burden from Postablation Weight-Loss Program: SORT-AF

May 06, 2021

Obesity is well known to promote atrial fibrillation (AF), and catheter ablation can dramatically cut back on AF prevalence. But assigning patients to a structured obesity-reduction program after AF ablation may not enhance the treatment's effect on AF burden, a novel randomized trial suggests.

Of 133 patients with symptomatic persistent or paroxysmal AF with a body mass index (BMI) in the 30 to 40 kg/m2 range, those assigned to the postablation obesity-reduction program lost weight but didn't benefit with less AF, compared with those who received standard care.

There were signs, however, that the weight-loss regimen — which included physical training, diet counseling, and other elements — may have stemmed the AF recurrence risk for patients with persistent AF but not those with the paroxysmal form.

That seemed especially true for those entering the three-center study with persistent AF who also improved in exercise capacity over the trial's 12 months. Their AF recurrence risk fell 23% compared with those with paroxysmal AF.

That post hoc finding shows the "impact and relevance" of lifestyle-related risk-factor modification "as an important adjunct" in the management of AF, observed Stephan Willems, MD, Asklepios Klinik St. Georg, Hamburg, Germany, when presenting the findings April 25 at the virtual European Heart Rhythm Association 2021 congress. They were published the same day in EP Europace.

The study, called the Supervised Obesity Reduction Trial in Atrial Fibrillation (SORT-AF), showed similar and significant falls in AF burden in both treatment groups, thereby demonstrating that AF ablation is both "safe and successful" in obese patients, Willems said.

Of note, most of the trial's patients had multiple AF risk factors in addition to obesity. And all participants, regardless of treatment assignment, were evaluated and offered therapy as needed for high blood pressure, sleep-disordered breathing, and diabetes. All received an implantable loop recorder (ILR) prior to ablation to monitor for rhythm abnormalities.

"The First of Its Kind"

SORT-AF follows numerous, mostly observational studies suggesting that weight loss, exercise, and risk-factor modification protocols can alleviate AF symptoms and prevalence. They include the LEGACY, REVERSE-AF, and CARDIO-FIT studies, along with ARREST-AF, in which patients who followed an intensive risk-factor management program showed significant improvements in symptoms, AF ablation success, and AF-free survival.

However, SORT-AF "is the first of its kind to evaluate the effect of a structured weight loss program after an ablation procedure in patients with paroxysmal or persistent atrial fibrillation," observed John Camm, MD, St. Georges University of London, as invited discussant after the Willems presentation.

The trial's post hoc finding of a "benefit" in those with persistent AF, he said, might carry more weight had the AF-recurrence subgroup analysis been prospectively defined.

Even if it had been prespecified, Camm said, it's "difficult" to accept a secondary outcome benefit when a trial fails to show a significant effect on the primary outcome.

SORT-AF was "a good attempt to demonstrate the potential value" of postablation weight loss. Although it failed to show such a benefit, he said, the trial at least proposes that such weight loss may prevent recurrences in patients who undergo ablation for persistent AF.

Explaining the Negative Finding

"Prior studies have shown that the weight-loss level associated with the greatest atrial fibrillation recurrence reduction is 10% of the baseline body weight," T. Jared Bunch, MD, University of Utah, Salt Lake City, pointed out for theheart.org | Medscape Cardiology.

The study's intervention group lost an average 4.5% in body weight, the control group less than 1.0%.

SORT-AF "shows that a formal multispecialty program after ablation can lead to sustained weight loss. However, the program may need modification to improve the likelihood of reaching a target weight-loss goal of greater than 10%," said Bunch, who was not part of the trial.

"The success of weight loss might have been too little to show an effect on AF burden," the published report agrees. "We believe this to be a major factor why the intention-to-treat analysis was negative."

Other potential explanations, it states, include lack of compliance in a third of those assigned to the weight-loss program. Also, the authors propose, AF burden might have declined more "if the weight loss would have been achieved by the time of ablation and not afterwards."

Bunch also noted that patients in the two groups achieved similar reductions in blood pressure over 12 months, "despite a greater weight loss in the interventional group." Elevated blood pressure "often drives atrial fibrillation onset and progression," so its management in the usual-care group "may have masked some of the benefits" of weight loss in the intervention group.

In patients who receive ablation for AF but don't achieve sustained weight loss, he said, "aggressive blood pressure management may offset some of the risks."

An Edge for Those With Persistent AF?

The trial's 133 patients, of whom 57% had persistent AF and the remainder paroxysmal AF, averaged 60 years of age, and 38% were women. After the comprehensive preablation evaluation, ILR implantation, and AF ablation by pulmonary vein isolation, Willems noted, 67 were assigned to the postablation structured weight-reduction program and 66 to usual care.

The intervention included "medical advice regarding nutrition and physical training on a regular basis" along with cognitive behavior therapy, he observed.

As described in the SORT-AF publication, the weight-reduction program "took place in a specialized obesity department as an interdisciplinary multimodal concept under the surveillance of a physician specialized for endocrinology."

The rate of noncompliance with the program was 19% after 3 months, 21% at 6 months, and 33% at 1 year. Mean BMI across the entire intervention group fell modestly but significantly from 34.9 to 33.4 kg/m2 (P < .001), compared with no change in the control group.

The primary endpoint, AF burden at 12 months excluding a 3-month blanking period, was similar in the two groups. Still, AF burden had plunged in both groups, from 21.6% to 3.79% in the intervention group and from 22.4% to 4.21% in the group that received standard care (P < .001 for both differences).

The drop in BMI for patients assigned to the intervention correlated with fewer AF recurrences among patients initially with persistent than with paroxysmal AF (P = .032). But the AF-recurrence hazard ratio (HR) for those with both persistent AF and improved exercise capacity was 0.77 (95% CI, 0.64 - 0.93).

That finding, Bunch said, "supports weight reduction as a strategy." In patients with paroxysmal AF, who in general have a lower AF burden, he observed, the lack of effect from weight loss "is likely due to the numbers enrolled in the study, which impact the ability to determine any differences."

SORT-AF was supported by a research grant from Abbott Medical GmbH. Willems discloses receiving grants and personal fees from Abbott and personal fees from Boston Scientific, Boehringer Ingelheim, Bristol Myers Squibb, Bayer Vital, Acutus, and Daiichi Sankyo. Disclosures for the other authors are in the report.

European Heart Rhythm Association (EHRA) 2021: Innovative Technology. Supervised obesity reduction trial for AF ablation patients: Results from the SORT-AF trial. Presented April 25, 2021.

Europace. Published online April 25, 2021. Abstract

Follow Steve Stiles on Twitter: @SteveStiles2. For more from theheart.org | Medscape Cardiology, follow us on Twitter and Facebook.

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