title: Rate-adaptive AV delay and exercise performance following cardiac resynchronization therapy.
abstract: BACKGROUND
  Physiological shortening of the atrioventricular (AV) interval with increasing heart rate is well documented in normal human beings and is an established component of dual-chamber pacing for bradycardia.
  
  
  OBJECTIVE
  To assess the effect of exercise on optimal AV delay and the impact of a patient-specific rate-adaptive AV delay (RAAVD) on exercise capacity in patients with heart failure following cardiac resynchronization therapy.
  
  
  METHODS
  Phase 1: We performed iterative AV optimization at rest and exercise in 52 cardiac resynchronization therapy patients in atrial-sensed mode (mean age 71.6 ± 9.2 years, 25% females). Phase 2: Subsequently, 20 consecutive volunteers from this group (mean age 69.2 ± 9.6 years, 15% females) underwent cardiopulmonary exercise testing with RAAVD individually programmed ON (RAAVD-ON) or OFF (RAAVD-OFF).
  
  
  RESULTS
  Phase 1: In 94% of the patients, there was a marked reduction (mean 50%) in optimal AV delay with exercise. The optimal resting vs exercise AV delay was 114.2 ± 29 ms at a heart rate of 64.4 ± 7.1 beats/min vs 57 ± 31 ms at a heart rate of 103 ± 13 beats/min (P < .001). No patients required an increase in AV delay with exercise, and 3 (6%) showed no change. Phase 2: With RAAVD-ON, significantly better exercise times were achieved (8.7 ± 3.2 minutes) compared with RAAVD-OFF (7.9 ± 3.2 minutes; P = .003), and there was a significant improvement in Vo(2)max (RAAVD-ON 16.1 ± 4.0 vs RAAVD-OFF 14.9 ± 3.7 mL/(kg · min); P = .024).
  
  
  CONCLUSIONS
  There was a dramatic reduction in optimal AV delay with physiological exercise in the majority of this heart failure cardiac resynchronization therapy cohort. Replicating this physiological response with a programmable RAAVD translated into a 10% improvement in exercise capacity.
authors: Department of Cardiology, St George's Healthcare NHS Trust, London, United Kingdom. nesan_s@hotmail.com
authors: Nesan
authors: N
authors: Shanmugam
authors: Oscar
authors: O
authors: Prada-Delgado
authors: Ana Garcia
authors: AG
authors: Campos
authors: Alex
authors: A
authors: Grimster
authors: Oswaldo
authors: O
authors: Valencia
authors: Aigul
authors: A
authors: Baltabaeva
authors: Sue
authors: S
authors: Jones
authors: Lisa
authors: L
authors: Anderson
mesh_terms: D000368:Aged; D001283:Atrioventricular Node / Q000502:physiology*; D002302:Cardiac Output / Q000502:physiology*; D058406:Cardiac Resynchronization Therapy / Q000379:methods*; D004452:Echocardiography; D004562:Electrocardiography; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test; D005260:Female; D006333:Heart Failure / Q000503:physiopathology / Q000628:therapy*; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D008297:Male; D015203:Reproducibility of Results; D018709:Statistics, Nonparametric