title: Impaired heart rate responses and exercise capacity in heart failure patients with paced baseline rhythms.
abstract: BACKGROUND
  Conduction system disease and beta-blocker therapy are both common among heart failure (HF) patients and contribute to increasing reliance on paced rhythms. We hypothesized that many HF patients dependent on pacing have suboptimal heart rate responses and associated limitations in exercise capacity.
  
  
  RESULTS
  We studied 122 HF patients (left ventricular ejection fractions ≤40%) referred for cardiopulmonary exercise testing, comparing those with pacing at baseline with those with native rhythms. The paced group (PG) had lower resting (71 ± 9 vs 75 ± 15 beats/min; P = .048) and peak heart rates (103 ± 22 vs 127 ± 27 beats/min; P < .0001). Although beta-blockers were prescribed with similar frequency in both groups (90% vs 85%), average dose was higher in the PG. Inotropic reserve (oxygen pulse) was similar in both groups (11.1 ± 3.3 vs 11.1 ± 3.4 mL/beat; P = .94), consistent with equivalent stroke volumes, but chronotropic incompetence was higher (95% vs 71%, P = .001) and peak VO(2) was lower (12.2 ± 3.4 vs 14.2 ± 4.1 mL/kg/min; P = .004) in the PG.
  
  
  CONCLUSIONS
  Chronotropic incompetence and exercise capacity are worse in HF patients depending on paced heart rate responses. This has implications for quality of life as well as advanced therapy choices based on exercise capacity. Reevaluating beta-blocker dosing and optimizing pacemaker programming may therefore benefit the growing population of HF patients with device-dependent rhythms.
authors.affiliation: Cardiovascular Division and Department of Medicine, Brigham and Women’s Hospital, Harvard Medical School, 75 Francis Street, Boston, MA 02115, USA.
authors.forename: Amaar
authors.initials: A
authors.lastname: Ujeyl
authors.forename: Lynne W
authors.initials: LW
authors.lastname: Stevenson
authors.forename: Erin K
authors.initials: EK
authors.lastname: West
authors.forename: Mahoto
authors.initials: M
authors.lastname: Kato
authors.forename: Mark
authors.initials: M
authors.lastname: Liszkowski
authors.forename: Patricia
authors.initials: P
authors.lastname: Campbell
authors.forename: Daniel E
authors.initials: DE
authors.lastname: Forman
mesh_terms: D000368:Aged; D002304:Cardiac Pacing, Artificial / Q000379:methods*; D005080:Exercise Test / Q000379:methods*; D017079:Exercise Tolerance / Q000502:physiology*; D005260:Female; D006333:Heart Failure / Q000175:diagnosis / Q000503:physiopathology* / Q000628:therapy*; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies