RecruitingDevice studySurveillance Trial of the Apple Watch in Reliable Burden Assessment in Unseen Recurrence of Surgically Treated AFThis is a prospective multicenter clinical study comparing the efficacy of the Apple Watch AFib History tool to the iRhythm Zio Patch monitoring device in quantifying atrial fibrillation (AF) burden after surgical ablation. Patients with AF and mitral valve (MV) disease who undergo a Cox-Maze IV procedure concomitant to MV surgery will be evaluated at serial timepoints for up to 1 year postoperatively. The trial will be conducted in the United States at the Cleveland Clinic in Cleveland, OH and at the Washington University School of Medicine in St. Louis, MO.