The impact of automatic threshold tracking on pulse generator longevity inpatients with different chronic stimulation thresholds

Automatic adjustment of the stimulation output of pacemakers to changing st imulation thresholds using the Autocapture feature increases patient safety and decreases energy consumption. This study examined the impact of Autoca pture on pulse generator longevity in patients with different chronic stimu lation thresholds. Eighty patients (mean age 79 +/- 9years; 37 men, 43 wome n) with Pacesetter Regency SR+ pacemakers were included in the study. Data were collected before discharge of the patients from the hospital, 6-12 wee ks postimplant, and then every 6-12 months. Pulse generator longevity was c alculated theoretically, assuming 100% stimulation with a stable threshold, at a pacing rate of 65 +/- 6 beats/min and 1% backup pulses. Theoretical p ulse generator longevity was calculated for low (< 1 V), intermediate ( <gr eater than or equal to> 1 V and < 2 V), and high (<greater than or equal to > 2 V) stimulation thresholds. Pulse generator longevity was compared among three groups: (A) Autocapture programmed On, (B) Autocapture programmed Of f, (C) theoretical calculations using thresholds of patients in group A wit h the stimulation voltage programmed at twice pacing threshold, or at a min imum of 2.4 V. The mean follow-up time since implantation was 19 +/- 8 mont hs. The calculated longevity benefits for patients in group A were 36%, 59% , and 30% compared to group B, and 29%, 32%, and 49% compared to group C in patients with low, intermediate, and high chronic stimulation thresholds, respectively. Theoretical calculations based on chronic stimulation thresho lds in our patient population with Regency SR+ pacemakers suggest that Auto capture may markedly prolong pulse generator longevity in patients with a b road range of long-term pacing thresholds.