title: Atrial adaptive rate pacing in sick sinus syndrome: effects on exercise capacity and arrhythmias.
abstract: OBJECTIVE
  To test the hypotheses that adaptive rate atrial (AAIR) pacing: significantly increases maximal exercise capacity, and results in significant suppression of supraventricular and ventricular arrhythmia compared with fixed rate atrial (AAI) pacing.
  
  
  METHODS
  Prospective, randomised, single blind, crossover study with maximal treadmill exercise testing and 24 hour ambulatory electrocardiographic monitoring in AAIR and AAI modes.
  
  
  METHODS
  Regional pacing centre.
  
  
  METHODS
  30 consecutive patients (mean SD age 65 (12) years) with sick sinus syndrome who required permanent pacing, without evidence of conduction disturbance on 12 lead electrocardiograms or 24 hour ambulatory electrocardiographic monitoring and without other cardiovascular or systemic disease.
  
  
  METHODS
  Activity sensing or minute ventilation driven systems (AAI/AAIR) were implanted alternately.
  
  
  RESULTS
  The mean (SD) peak heart rate in AAI mode was 122(28)v 130(22) in AAIR mode (p < 0.02) for the whole group and 104(17) v 120(5) (p < 0.003) for the patients with chronotropic incompetence. Exercise time was 12.3 (4.1) minutes in AAI and 12.3 (3.8) minutes in AAIR mode (NS) in the chronotropically incompetent patients. There were no significant differences in the Borg scores at peak exercise in AAI v AAIR mode in either group. The frequency per hour of atrial and ventricular arrhythmias showed no significant differences between the two modes in either the group as a whole or in the subgroups with chronotropic incompetence.
  
  
  CONCLUSIONS
  AAIR pacing confers little benefit in sick sinus syndrome compared with AAI pacing.
authors.affiliation: Department of Cardiological Sciences, St George's Hospital Medical School, London.
authors.forename: G A
authors.initials: GA
authors.lastname: Haywood
authors.forename: D
authors.initials: D
authors.lastname: Katritsis
authors.forename: J
authors.initials: J
authors.lastname: Ward
authors.forename: M
authors.initials: M
authors.lastname: Leigh-Jones
authors.forename: D E
authors.initials: DE
authors.lastname: Ward
authors.forename: A J
authors.initials: AJ
authors.lastname: Camm
mesh_terms: D000368:Aged; D001145:Arrhythmias, Cardiac / Q000503:physiopathology / Q000517:prevention & control*; D002304:Cardiac Pacing, Artificial / Q000379:methods*; D017079:Exercise Tolerance / Q000502:physiology*; D005260:Female; D006325:Heart Atria; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012804:Sick Sinus Syndrome / Q000503:physiopathology / Q000628:therapy*; D016037:Single-Blind Method