Safety and Efficacy of the CoolCryo System for Cardiac Cryoablation in the Treatment of Atrial Fibrillation

This study is testing a device called the CoolCryo System for cardiac cryoablation — a procedure that uses extreme cold to destroy abnormal heart tissue — in patients who have atrial fibrillation and also need mitral valve surgery. The goal is to treat both problems at the same time. **You may be eligible if...** - You are 18 or older and have been scheduled for mitral valve surgery (valve repair or replacement) - You have also been diagnosed with atrial fibrillation (irregular heartbeat) for at least 3 months before surgery - You have signed informed consent **You may NOT be eligible if...** - You have thyroid problems, active infection, or certain electrolyte imbalances that could be causing the atrial fibrillation - You have had prior heart surgery - Your left atrium (a heart chamber) is very enlarged - You are pregnant, breastfeeding, or planning pregnancy within 6 months - You are currently on biological therapy or have less than 12 months life expectancy Talk to your doctor to see if this trial is right for you.