Patients will complete a 6-min walk test at the baseline study visit to screen for CI based on the intrinsic heart rate achieved during the walk while pacemaker set to DDD/VVI with both sensors set to passive. All patients that are enrolled in the study will get treadmill exercise stress test by chronotropic assessment exercise protocol (CAEP) to confirm CI. Patients will be determined to have CI by completing a maximal effort exercise treadmill stress test with peak perceived exertion by Borg scale of >16 (18) with the pacemaker programmed to DDD/VVI with both device sensors set to passive. Patients that do not meet the criteria of CI after CAEP treadmill test will not continue in the trial.