Importance of heart rate during exercise for response to cardiac resynchronization therapy.
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.
Maass
Alexander H
AH
Department of Cardiology, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands.
Buck
Sandra
S
Nieuwland
Wybe
W
Brügemann
Johan
J
van Veldhuisen
Dirk J
DJ
Van Gelder
Isabelle C
IC
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