title: Rate responsive pacing using cardiac resynchronization therapy in patients with chronotropic incompetence and chronic heart failure.
abstract: OBJECTIVE
  Chronotropic incompetence (CI) is a common finding in patients with advanced chronic heart failure (CHF) and is associated with a worse functional capacity. Whether rate responsive pacing with cardiac resynchronization therapy (CRT) would acutely improve exercise performance in patients with advanced CHF and severe CI (<70% age-predicted maximum heart rate) is unknown.
  
  
  RESULTS
  Patients (n = 13) with CHF, a CRT device, and severe CI were randomized in a double-blind crossover pilot study to either DDD (control) or DDDR (rate responsive) pacing. Six minutes walk test (6MWT) distance, oxygen consumption at anaerobic threshold (VO(2) @ AT), and maximal oxygen consumption (VO(2) max) were measured. One week later, testing was repeated in the alternate pacing mode. Rate responsive pacing commenced with standard settings in only 9 of 13 (69%) patients. In these 9 subjects, 6MWT distance improved acutely from 358.5 ± 40.7 to 376.8 ± 24.5 m with DDDR pacing (P< 0.05). VO(2) max did not improve with DDDR pacing (14.0 ± 3.2 mL/kg/min) compared with DDD pacing (13.9 ± 3.0 mL/kg/min; P= 0.69). VO(2) @ AT tended towards improvement with DDDR pacing (10.8 ± 2.9 mL/kg/min) compared with DDD pacing (9.6 ± 1.8 mL/kg/min; P= 0.29). There was a linear relationship between the increase in heart rate at minute 3 during rate responsive pacing and improvement in VO(2) @ AT (r = 0.83, P< 0.05).
  
  
  CONCLUSIONS
  When rate responsive pacing using a CRT device is achieved in patients with advanced CHF and severe CI, parameters of aerobic exercise performance improve acutely. Routine exercise testing to ensure successful restoration of heart rate response may be beneficial to optimize CRT settings in this patient population.
authors.affiliation: Division of Cardiology, Department of Medicine, Columbia University Medical Center, 622 West 168th Street, New York, NY 10032, USA.
authors.forename: Daniel B
authors.initials: DB
authors.lastname: Sims
authors.forename: Andrea
authors.initials: A
authors.lastname: Mignatti
authors.forename: Paolo C
authors.initials: PC
authors.lastname: Colombo
authors.forename: Nir
authors.initials: N
authors.lastname: Uriel
authors.forename: Luis I
authors.initials: LI
authors.lastname: Garcia
authors.forename: Frederick A
authors.initials: FA
authors.lastname: Ehlert
authors.forename: Ulrich P
authors.initials: UP
authors.lastname: Jorde
mesh_terms: D000328:Adult; D000368:Aged; D001145:Arrhythmias, Cardiac / Q000503:physiopathology* / Q000628:therapy*; D058406:Cardiac Resynchronization Therapy / Q000379:methods*; D058409:Cardiac Resynchronization Therapy Devices; D002908:Chronic Disease; D018592:Cross-Over Studies; D004311:Double-Blind Method; D017079:Exercise Tolerance / Q000502:physiology; D005260:Female; D006333:Heart Failure / Q000503:physiopathology / Q000628:therapy*; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010101:Oxygen Consumption / Q000502:physiology; D010865:Pilot Projects; D016896:Treatment Outcome