Clinical evaluation of a pacemaker algorithm that adjusts the pacing rate during sleep using activity variance

Even though rate responsive pacemakers are able to regulate pacing rates ba sed on sensor activity, they are set with a minimum rate that is not adjust ed to provide rate decreases during sleep. The aim of this study was to eva luate the performance of the "Sleep Rate" feature, as com pared to patient diaries and a validated method that identifies sleep from wrist actigraphy. In 19 patients (15 men; age 69 +/- 8 years) with Pacesetter Trilogy DR + p acemakers, the base rate and the sleep rate were set to 80 and 50 ppm, resp ectively. When the patients returned 2 days later, data recorded by the pac emaker and wrist actigraph were analyzed to find the agreement in correspon ding sleep/wake periods. In 17 (89%) patients, the pacemaker went into the sleep mode. The total sleep time derived from actigraphy significantly exce eded the time during which the pacemaker was in sleep mode (1156.8 +/- 83.4 vs 307.3 +/- 77.2 minutes). Frequent reversions out of the sleep mode limi ted the total sleep time derived from the pacemaker. Cumulative analysis of the pacemaker data showed that the maximum time in the sleep mode was 78 m inutes, and exceeded 1 hour in six instances, 30 minutes in 32 instances, a nd 15 minutes in 83 instances. Epoch by epoch comparisons revealed a good a greement (93.6 +/- 1.8%) during wakefulness between the corresponding actig raph and pacemaker epochs. However, only 24.6 +/- 3.7% of the corresponding epochs during sleep were identical, and the overall agreement was 54.4 +/- 3.7%. Except for one patient who reported palpitations, patients did not s uffer from a pacemaker rate change. The Sleep Rate feature provides rate re duction during sleep, while assuring rapid frequency response during physic al activity. However, the current algorithm does not allow long periods of slow pacing rate during continuous sleep, possibly due to its conservative design and the presence of movement arousals, which has to be improved in f uture generation algorithms.