Metformin reduces Afib after ablation

Obese or overweight non-diabetic adults with atrial fibrillation (Afib) who take the diabetes medication metformin after a catheter ablation are more likely to remain free of AFib for a year than similar patients who do not take the drug, researchers report.

These findings were presented on Nov. 9, 2025 at the American Heart Association Scientific Sessions 2025.

“Lifestyle and risk factor modification efforts are essential to treating AFib and according to the results of our study could be aided by taking metformin,” said Amish Deshmukh, M.D., lead author of the study and clinical assistant professor of medicine at the University of Michigan in Ann Arbor.

Investigators in The Metformin as an Adjunctive Therapy to Catheter Ablation of Atrial Fibrillation (META-AF) study enrolled adults with AFib and obesity or overweight.  All subjects underwent ablation and then were randomized to receive either usual care (lifestyle education about physical activity, healthy eating, sleep and managing other medical conditions) or usual care plus metformin.

The study included 99 adults (average age of 63 years; 70% male) with AFib, 70% of whom were obese and 30% of whom were overweight.

Patients were excluded from enrollment if they had been diagnosed with Type 1 or Type 2 diabetes.

Also, patients using other drugs to treat diabetes and those for whom metformin was contraindicated were excluded.

All subjects used blood thinners during the trial to reduce the risk of stroke.

No placebo was used. The subjects were aware of which treatment group they were in (49 were randomized to metformin and 50 to usual care).

During the year of the trial, the investigators determined that 78% of the metformin subjects and 58% of the usual-care group had no episodes of AFib lasting 30 seconds or longer.

Fewer subjects in the metformin group needed repeat ablation or electric shock to restore a normal heart rhythm during an AFib episode (6% versus 16% for usual care.)

Metformin subjects had less frequent AFib episodes compared to the usual care subjects (8% versus 16%, respectively).

Eight percent of the subjects in the metformin group required anti-arrhythmia medications during the trial period compared to 18% in the usual care group.

The investigators did not attribute any of the metformin-related results to weight loss since it was not significant in the metformin group.

“I would suggest conducting a larger study to investigate metformin and other diabetes treatments. We know that many of these medications offer cardiovascular benefits, and we are starting to gain a better understanding of how they might specifically benefit patients with arrhythmias. A study comparing various medications would be valuable to confirm our findings and also to address questions about tolerability, the feasibility of long-term use and costs,” Deshmukh said.