© 2008 European Society of Cardiology
Chronotropic incompetence, beta-blockers, and functional capacity in advanced congestive heart failure: Time to pace?
a Division of Cardiology, New York Presbyterian Hospital, Columbia University College of Physicians and Surgeons United States
b Heart Failure Program, Leon Charney Division of Cardiology, New York University School of Medicine United States
* Corresponding author. College of Physicians & Surgeons, Columbia University, Department of Medicine, Division of Cardiology, 630 West 168th Street, Box #93, New York, NY 10032, United States. Tel.: +1 212 305 4736; fax: +1 212 305 4825. E-mail address: upj1{at}columbia.edu (U. P. Jorde).
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Abstract |
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Background: Chronotropic incompetence (CI) is often seen in subjects with chronic congestive heart failure (CHF). The prevalence of CI, its mechanisms and association with beta-blocker use as well as exercise capacity have not been clearly defined.
Methods and results: Cardiopulmonary exercise tolerance testing data for 278 consecutive patients with systolic CHF was analyzed. CI, defined as the inability to reach 80% of maximally predicted heart rate was present in 128 of 278 subjects (46%). The prevalence of CI was highest in those with most impaired exercise capacity (72, 48, and 24% for subjects with a VO2 of <14.0, 14.0–20.0, and >20.0ml/kg/min respectively; p=0.001). While subjects with CI had lower peak exercise heart rate (114 vs. 152 bpm), and lower peak VO2 (15.4 vs. 19.9 ml/kg/min), they were equally likely to be on chronic beta-blocker therapy (74% vs. 71%; p=0.51).
Heart rate and norepinephrine (NE) levels were measured during exercise in a separate cohort of 24 subjects with CHF. There was no difference in beta-blocker dose between subjects with and without CI, however, exercise induced NE release and Chronotropic Responsiveness Index, a measure of post-synaptic beta-receptor sensitivity to NE, were lower in subjects with CI (1687±911 vs. 2593±1451pg/ml p=0.08; CRI 12.7±5.7 vs. 22.1±4.7, p=0.002).
Conclusions: CI occurs in >70% of subjects with advanced systolic CHF irrespective of beta-blocker use and is associated with a trend toward impaired NE release, post-synaptic beta-receptor desensitization and reduced exercise capacity.
Key Words: CHF • Chronotropic Incompetence • Beta-blocker • Exercise
Received May 2, 2007; Revised September 10, 2007; Accepted November 14, 2007
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