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Chronotropic incompetence response to exercise in congestive heart failure, relationship with the cardiac autonomic
F Roche1, V Pichot, A Da Costa
1Laboratoire de Physiologie GIP-Exercice, Service d'Exploration Fonctionnelle CardioRespiratoire, CHU Nord, Faculté de Médecine Jacques Lisfranc, Université Jean Monnet, Saint-Etienne, France.
Insights
Chronotropic incompetence (CI) in heart failure limits exercise capacity. Reduced cardiac sympathetic tone, not baroreflex sensitivity, is linked to this impaired heart rate response in CHF patients.
Area of Science:
- Cardiology
- Exercise Physiology
- Autonomic Nervous System Research
Background:
- Chronic heart failure (CHF) often presents with chronotropic incompetence (CI), characterized by an attenuated heart rate response to exercise, significantly limiting patient capacity.
- The underlying mechanisms of CI in CHF, specifically the roles of cardiac vagal tone, baroreflex sensitivity, and cardiac sympathetic responsiveness, require further elucidation.
Purpose of the Study:
- To investigate the contribution of depressed baroreflex sensitivity versus impaired cardiac sympathetic responsiveness to chronotropic incompetence in patients with chronic heart failure.
- To analyze the relationship between heart rate reserve and autonomic nervous system markers in CHF patients with and without CI.
Main Methods:
- Assessed spontaneous cardiac baroreflex sensitivity (BRS) and heart rate variability (HRV) using sequence, spectral, and time-domain analyses in 21 chronic CHF patients.
- Conducted symptom-limited exercise tests with gas exchange measurements to determine heart rate reserve (%HRR) and identify patients with CI (defined as <80% HRR).
Main Results:
- Chronotropic incompetence (CI) was observed in 66% of the CHF patients studied.
- Patients with CI exhibited significantly lower low-frequency power of HRV in normalized units (LFnu) and SDNN compared to those without CI, despite no significant differences in BRS.
- Percentage of HRR significantly correlated with LFnu and SDNN, but not with BRS.
Conclusions:
- Autonomic nervous system dysfunction in CHF is complex, involving both sympathetic and parasympathetic components.
- Basal depressed cardiac sympathetic tone appears to be a more significant contributor to the impaired heart rate response during exercise in CHF patients with CI than depressed baroreflex sensitivity.
Abstract:
In chronic congestive heart failure (CHF), attenuated heart rate response to exercise, a manifestation of chronotropic incompetence (CI), contributes to limiting exercise capacity. The present study was thus conducted to evaluate the respective role of chronic attenuation of cardiac vagal tone associated with depressed baroreflex sensitivity or affected cardiac sympathetic responsiveness in CHF patients with CI. Spontaneous cardiac baroreflex sensitivity (BRS) assessed by sequence method and spectral- and time-domain analysis of heart rate variability (HRV) were analysed in 21 chronic CHF patients. All patients performed a symptom-limited exercise test with measurement of gas exchange. Chronic incompetence which was defined as failure to achieve > or =80% of the heart rate reserve (%HRR) given by (HRpeak - HRrest)/(predictive maximal heart rate - HRrest) was observed in 14 (66%) patients. There was no significant difference in age, heart rate, peak oxygen uptake or left ventricular ejection fraction between the patients with and without CI. Although there was no significant difference in BRS, low frequency power of HRV in normalized units (LFnu) and SDNN were significantly lower in CI patients. Percentage of HRR correlated significantly with LFnu on 15 min (r=0.64, P<0.005) and, with LFnu on 24 h (r=0.52, P<0.01), SDNN (r=0.48, P=0.03) and SDANN (r=0.48, P=0.03), but not BRS (r=0.04, P=NS). Autonomic nervous system derangement is a complex process in CHF. The role of basal depressed cardiac sympathetic tone seems to contribute more closely than depressed baroreflex sensitivity to the impaired heart rate response to exercise frequently observed in CHF patients.