title: Automatic adjustment of pacing output in the clinical setting.
abstract: BACKGROUND
  AutoCapture (AC) is a programmable feature that enables the pacemaker to both track the capture threshold and automatically adjust the output on a beat-by-beat basis. Although AC safely and significantly reduces the current drainage, some authors have argued that the longevity benefit of such a system is overstated. This study aims to estimate the longevity extension that can be obtained, in the clinical routine, by turning the AC on in comparison to pacemakers programmed to operate at the shipped and manually optimized output.
  
  
  METHODS
  We selected 83 consecutive patients who received implanted St Jude's Affinity pacemakers >6 months earlier. Eight patients died or were lost to follow-up and in 9 subjects the AC could not be turned on. In the remaining 66 patients, current drain and estimated longevity were compared in 3 situations: (1) AC on; (2) AC off, optimized programming (100%-150% voltage threshold); (3) AC off, shipped output (3.5 V).
  
  
  RESULTS
  Five patients had large variations (>1 V) of the AC threshold. Current drainage was 8.0 +/- 0.9 mA in the AC group, 8.7 +/- 1.8 mA with AC off and optimized programming, and 11.3 +/- 2.3 mA at shipped output (P <.01). Estimated longevity was significantly extended (P <.01) by AC (12.1 +/- 1.0 years) when compared to shipped (8.9 +/- 1.7 years) and optimized programming (11.3 +/- 1.4 years).
  
  
  CONCLUSIONS
  Reprogramming the pacemaker output significantly enhanced its estimated longevity; AC added a moderate but significant extension over manual reprogramming and was associated with increased safety in patients with large ventricular threshold variations.
authors.affiliation: Pacemaker Laboratory, Hospital das Clínicas, Belo Horizonte, Brazil. tom@hc.ufmg.br
authors.forename: Antonio Luiz P
authors.initials: AL
authors.lastname: Ribeiro
authors.forename: Leonor G
authors.initials: LG
authors.lastname: Rincón
authors.forename: Bruna G
authors.initials: BG
authors.lastname: Oliveira
authors.forename: Caio R
authors.initials: CR
authors.lastname: Vinha
authors.forename: Douglas
authors.initials: D
authors.lastname: Melatto
authors.forename: Ana A
authors.initials: AA
authors.lastname: Torres
authors.forename: Vladimir C V
authors.initials: VC
authors.lastname: Barros
authors.forename: Paul A
authors.initials: PA
authors.lastname: Levine
mesh_terms: D000465:Algorithms; D002138:Calibration; D002304:Cardiac Pacing, Artificial; D011211:Electric Power Supplies; D004868:Equipment Failure; D005260:Female; D006327:Heart Block / Q000503:physiopathology / Q000628:therapy*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010138:Pacemaker, Artificial; D012804:Sick Sinus Syndrome / Q000628:therapy*; D013997:Time Factors