METFORMIN FOR ATRIAL FIBRILLATION

The aim of this multicenter, pragmatic, open-label, randomized, placebo-controlled clinical trial is to test whether repurposing metformin for the treatment of atrial fibrillation will be effective in decreasing patients' hospitalization, adverse major cardiovascular events, and non-cancer death. Participants will be randomized into 2 study arms (385 participant each), whereby: * The Metformin Group (MG): will receive metformin oral tablets in addition to the standard rate/rhythm control strategy and anticoagulation. * The Placebo Control Group (PCG): will receive placebo oral tablets as a control group in addition to the standard rate/rhythm control strategy and anticoagulation. Then both arms will be compared according to the these endpoints: * The primary endpoint is hospitalization due to an episodic AF or an AF with a rapid or slow ventricular response (in the case of permanent AF). * The secondary endpoint is a composite of non-fatal major cardiovascular adverse events or non-cancer death. The non-fatal major cardiovascular adverse events include: * Hospitalization due to heart failure. * Non-fatal myocardial infarction. * Non-fatal stroke. * Hospitalization due to unstable angina.