title: Proportionality of rate response to metabolic workload provided by a rate adaptive pacemaker with automatic rate profile optimization.
abstract: OBJECTIVE
  The rate response of a pacemaker (PM) was compared with the sinus rate in patients during repeated exercise tests, at different settings of the rate response parameters.
  
  
  RESULTS
  In patients with paroxysmal sick sinus syndrome (n=3) or atrioventricular block (n=8), a rate responsive PM was implanted. The activity-dependent pacing rate is represented by the sensor indicated rate (SIR). Each patient performed a treadmill test at 1 month, 1 year, and 2 years after implantation. Prior to the 1 and 2 year tests PM parameters were changed to produce a larger rate increase, especially at moderate levels of daily life activity. During the tests the O(2) consumption and CO(2) production were measured, breath-by-breath, to determine the workload and the anaerobic threshold. On average the workload (oxygen consumption), the patient's sinus rate, and the SIR, showed a linear increase with the workload imposed by the treadmill. In the 1 month and 1 year test the SIR was much lower than the spontaneous rhythm, especially at low or moderate workloads. On the more dynamic setting of several rate adaptive parameters at 2 years, the SIR changed significantly and was close to the spontaneous HR.
  
  
  CONCLUSIONS
  The examined PM provides a paced heart rate that is proportional to the workload. For the first time the effect of reprogramming rate response parameters to produce an SIR that is similar to the sinus rate is shown in this study.
authors.affiliation: Institute of Medicine, Department of Heart Disease, University of Bergen, Bergen, Norway. peter.schuster@med.uib.no
authors.forename: Peter
authors.initials: P
authors.lastname: Schuster
authors.forename: Svein
authors.initials: S
authors.lastname: Faerestrand
authors.forename: Ole-Jorgen
authors.initials: OJ
authors.lastname: Ohm
authors.forename: Vincent
authors.initials: V
authors.lastname: Schouten
mesh_terms: D000368:Aged; D005080:Exercise Test; D005260:Female; D006327:Heart Block / Q000503:physiopathology / Q000628:therapy*; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D008297:Male; D010101:Oxygen Consumption / Q000502:physiology; D010138:Pacemaker, Artificial; D011446:Prospective Studies; D012804:Sick Sinus Syndrome / Q000503:physiopathology / Q000628:therapy*; D016896:Treatment Outcome