title: Importance of heart rate during exercise for response to cardiac resynchronization therapy.
abstract: BACKGROUND
  Cardiac resynchronization therapy (CRT) is an established therapy for patients with severe heart failure and mechanical dyssynchrony. Response is only achieved in 60-70% of patients.
  
  
  OBJECTIVE
  To study exercise-related factors predicting response to CRT.
  
  
  METHODS
  We retrospectively examined consecutive patients in whom a CRT device was implanted. All underwent cardiopulmonary exercise testing prior to implantation and after 6 months. The occurrence of chronotropic incompetence and heart rates exceeding the upper rate of the device, thereby compromising biventricular stimulation, was studied. Response was defined as a decrease in LVESV of 10% or more after 6 months.
  
  
  RESULTS
  We included 144 patients. After 6 months 86 (60%) patients were responders. Peak VO2 significantly increased in responders. Chronotropic incompetence was more frequently seen in nonresponders (21 [36%] vs 9 [10%], P = 0.03), mostly in patients in SR. At moderate exercise, defined as 25% of the maximal exercise tolerance, that is, comparable to daily life exercise, nonresponders more frequently went above the upper rate of the device (13 [22%] vs 2 [3%], P < 0.0001), most of whom were patients in permanent AF. Multivariate analysis revealed heart rates not exceeding the upper rate of the device during moderate exercise (OR 15.8 [3.3-76.5], P = 0.001) and nonischemic cardiomyopathy (OR 2.4 [1.0-5.7], P = 0.04) as predictive for response.
  
  
  CONCLUSIONS
  Heart rate exceeding the upper rate during moderate exercise is an independent predictor for nonresponse to CRT in patients with AF, whereas chronotropic incompetence is a predictor for patients in SR.
authors.affiliation: Department of Cardiology, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands.
authors.forename: Alexander H
authors.initials: AH
authors.lastname: Maass
authors.forename: Sandra
authors.initials: S
authors.lastname: Buck
authors.forename: Wybe
authors.initials: W
authors.lastname: Nieuwland
authors.forename: Johan
authors.initials: J
authors.lastname: Brügemann
authors.forename: Dirk J
authors.initials: DJ
authors.lastname: van Veldhuisen
authors.forename: Isabelle C
authors.initials: IC
authors.lastname: Van Gelder
mesh_terms: D000368:Aged; D015308:Anaerobic Threshold; D001281:Atrial Fibrillation / Q000175:diagnosis / Q000503:physiopathology / Q000628:therapy*; D017147:Defibrillators, Implantable; D004554:Electric Countershock / Q000295:instrumentation*; D004562:Electrocardiography; D005080:Exercise Test; D017079:Exercise Tolerance; D005260:Female; D006333:Heart Failure / Q000175:diagnosis / Q000503:physiopathology / Q000628:therapy*; D006339:Heart Rate; D006801:Humans; D008297:Male; D008875:Middle Aged; D016017:Odds Ratio; D010101:Oxygen Consumption; D011237:Predictive Value of Tests; D012189:Retrospective Studies; D018570:Risk Assessment; D012307:Risk Factors; D012720:Severity of Illness Index; D016896:Treatment Outcome