title: Impact of cardiac resynchronization therapy on exercise performance, functional capacity, and quality of life in systolic heart failure with QRS prolongation: COMPANION trial sub-study.
abstract: BACKGROUND
  A total of 405 participants in the Comparison of Medical Therapy, Pacing, and Defibrillation in Heart Failure trial were prospectively enrolled in an exercise sub-study designed to study the influence of cardiac resynchronization therapy (CRT) on measures of exercise capacity, functional capacity, and quality of life (QOL).
  
  
  RESULTS
  Substudy eligibility included New York Heart Association (NYHA) functional Class III or IV heart failure, left ventricular ejection fraction < or =0.35, QRS interval of > or =120 ms, normal sinus rhythm, a heart failure hospitalization (or equivalent) within 1 year, a peak VO2 < or =22 mL x kg x min, the ability to walk 150 to 425 meters in 6 minutes, forced expiratory volume in 1 second/forced vital capacity > or =50%, and no clinical indication for a pacemaker or implantable cardioverter-defibrillator. Patients were randomized in a 1:4 ratio to optimal medical therapy (OPT) or to OPT plus CRT. Cardiopulmonary exercise testing (peak VO2 and 6-minute walk distance [6MWD]) and assessment of NYHA functional class and QOL were assessed at baseline and at 3 and 6 months of assigned therapy. There was no significant improvement in peak VO2 at 6 months in the CRT group compared with the OPT group (+0.63 mL x kg x min) by unadjusted analysis (P = .05) or by analyses adjusted for missing data. Thus the primary end point of the study was not met. There was significantly greater improvement in the 6MWD in the CRT group compared with the OPT group at both 3 and 6 months by both statistical methods (P < or = .045). Likewise, a greater proportion of CRT patients improved by 1 or more NYHA functional classes (P < .01) at 3 months and had better QOL scores (P < .01) at 3 and 6 months compared with the OPT patients. Baseline peak VO2 predicted clinical events (time to death, time to death or first hospitalization, or time to death and first heart failure hospitalization: P < .05) in CRT participants.
  
  
  CONCLUSIONS
  CRT patients with moderate to advanced symptoms of systolic heart failure and prolonged QRS intervals benefit from the addition of CRT to OPT in terms of exercise capacity, functional status, and QOL. CRT should be considered standard therapy in this select group of heart failure patients.
authors.affiliation: University of California, San Francisco Medical Center, San Francisco, CA, USA.
authors.forename: Teresa
authors.initials: T
authors.lastname: De Marco
authors.forename: Eugene
authors.initials: E
authors.lastname: Wolfel
authors.forename: Arthur M
authors.initials: AM
authors.lastname: Feldman
authors.forename: Brian
authors.initials: B
authors.lastname: Lowes
authors.forename: Michael B
authors.initials: MB
authors.lastname: Higginbotham
authors.forename: Jalal K
authors.initials: JK
authors.lastname: Ghali
authors.forename: Lynne
authors.initials: L
authors.lastname: Wagoner
authors.forename: Philip C
authors.initials: PC
authors.lastname: Kirlin
authors.forename: Jerry D
authors.initials: JD
authors.lastname: Kennett
authors.forename: Satish
authors.initials: S
authors.lastname: Goel
authors.forename: Leslie A
authors.initials: LA
authors.lastname: Saxon
authors.forename: John P
authors.initials: JP
authors.lastname: Boehmer
authors.forename: David
authors.initials: D
authors.lastname: Mann
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Galle
authors.forename: Fred
authors.initials: F
authors.lastname: Ecklund
authors.forename: Patrick
authors.initials: P
authors.lastname: Yong
authors.forename: Michael R
authors.initials: MR
authors.lastname: Bristow
mesh_terms: D000368:Aged; D003131:Combined Modality Therapy; D017147:Defibrillators, Implantable; D004562:Electrocardiography; D017079:Exercise Tolerance / Q000502:physiology*; D005260:Female; D005500:Follow-Up Studies; D054143:Heart Failure, Systolic / Q000175:diagnosis / Q000401:mortality / Q000628:therapy*; D006334:Heart Function Tests; D006801:Humans; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D010138:Pacemaker, Artificial; D011336:Probability; D011788:Quality of Life; D012016:Reference Values; D012720:Severity of Illness Index; D013318:Stroke Volume / Q000502:physiology; D016019:Survival Analysis; D016896:Treatment Outcome; D020257:Ventricular Remodeling / Q000502:physiology