Surveillance Trial of the Apple Watch in Reliable Burden Assessment in Unseen Recurrence of Surgically Treated AF

This study is testing whether an Apple Watch can reliably monitor and measure the burden of atrial fibrillation (AFib) — how much of the time a person's heart is in an irregular rhythm — after they have had surgical treatment (called the Cox-Maze procedure) to correct AFib. **You may be eligible if...** - You are 22 years or older - You have a documented history of atrial fibrillation - You are scheduled to have mitral valve surgery along with a surgical ablation procedure (Cox-Maze IV) to treat your AFib - You are having your left atrial appendage closed off during the same surgery **You may NOT be eligible if...** - You are having an emergency (non-elective) surgery - You already have a pacemaker or implanted cardiac device that might interfere - You are not able or willing to wear the Apple Watch as required Talk to your doctor to see if this trial is right for you.