RecruitingDevice studySingle Chamber Atrial Leadless Pacing for Isolated Sinus Node DysfunctionThe study aims to evaluate the following: 1) the incidence of new onset atrial fibrillation in patients with an atrial leadless pacemaker, 2) the need for upgrade from a standalone atrial leadless pacemaker to a dual chamber leadless pacemaker system, and 3) to compare the battery longevity of the Aveir AR at two years with the battery longevity of subjects implanted with dual chamber leadless pacemakers in the Aveir DR i2i study.