title: Impact of automatic threshold capture on pulse generator longevity.
abstract: BACKGROUND
  The automatic, threshold tracking, pacing algorithm developed by St. Jude Medical, verifies ventricular capture beat by beat by recognizing the evoked response following each pacemaker stimulus. This function was assumed to be not only energy saving but safe. This study estimated the extension in longevity obtained by AutoCapture (AC) compared with pacemakers programmed to manually optimized, nominal output.
  
  
  METHODS
  Thirty-four patients who received the St. Jude Affinity series pacemaker were included in the study. The following measurements were taken: stimulation and sensing threshold, impedance of leads, evoked response and polarization signals by 3501 programmer during followup, battery current and battery impedance under different conditions. For longevity comparison, ventricular output was programmed under three different conditions: (1) AC on; (2) AC off with nominal output, and (3) AC off with pacing output set at twice the pacing threshold with a minimum of 2.0 V. Patients were divided into two groups: chronic threshold is higher or lower than 1 V. The efficacy of AC was evaluated.
  
  
  RESULTS
  Current drain in the AC on group, AC off with optimized programming or nominal output was (14.33 +/- 2.84) mA, (16.74 +/- 2.75) mA and (18.4 +/- 2.44) mA, respectively (AC on or AC off with optimized programming vs. nominal output, P < 0.01). Estimated longevity was significantly extended by AC on when compared with nominal setting [(103 +/- 27) months, (80 +/- 24) months, P < 0.01). Furthermore, compared with the optimized programming, AC extends the longevity when the pacing threshold is higher than 1 V.
  
  
  CONCLUSIONS
  AC could significantly prolong pacemaker longevity; especially in the patient with high pacing threshold.
authors.affiliation: Centre of Arrhythmia Diagnosis and Treatment, Fuwai Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100037, China.
authors.forename: Ruo-han
authors.initials: RH
authors.lastname: Chen
authors.forename: Ke-ping
authors.initials: KP
authors.lastname: Chen
authors.forename: Fang-zheng
authors.initials: FZ
authors.lastname: Wang
authors.forename: Wei
authors.initials: W
authors.lastname: Hua
authors.forename: Shu
authors.initials: S
authors.lastname: Zhang
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010138:Pacemaker, Artificial; D013997:Time Factors