Background: The response to moderate exercise at altitude in heart failure (HF) is unknown. Methods and results: We evaluated 30 HF patients, (NYHA I-III, 25 M/5 F; 59 ± 10 years; LVEF = 39.6 ± 7.1%), in stable clinical conditions, treated with carvedilol at the maximal tolerated dose. We performed a maximal cardiopulmonary exercise test (CPET) with ramp protocol at sea level to evaluate patients' performance and two moderate intensity constant workload CPETs (50% of peak workload) at sea level (normoxia) and simulated altitude (hypoxia). Oxygen uptake ( $${\stackrel{\cdot }{\hbox{ V }}\hbox{ O }}_{2}$$ ) and heart rate (HR) on-kinetics at constant workload were assessed calculating the time constant (τ) with a monoexponential equation. $${\stackrel{\cdot }{\hbox{ V }}\hbox{ O }}_{2}$$ and HR were higher in hypoxia (0.944 ± 0.233 vs 1.031 ± 0.264 l/min; 100 ± 23 vs 108 ± 22 bpm; p < 0.001). On-kinetics showed a different behavior of τ being $${\stackrel{\cdot }{\hbox{ V }}\hbox{ O }}_{2}$$ faster in hypoxia (67.1 ± 23.0 vs. 56.3 ± 19.7 s; p = 0.026) and HR faster in normoxia (49.3 ± 19.4 vs. 62.2 ± 22.5 s; p = 0.018). Ten patients, who lowered oxygen kinetics in hypoxia, had greater HR increase during maximal CPET suggesting lower functional betablockade. The higher τ of $${\stackrel{\cdot }{\hbox{ V }}\hbox{ O }}_{2}$$ in hypoxia is likely to be due to a peripheral effect of carvedilol mediated either by β- or α-receptor. Conclusion: HF patients performing moderate exercise at 2000 m simulated altitude have 20% $${\stackrel{\cdot }{\hbox{ V }}\hbox{ O }}_{2}$$ increase without trouble at the beginning of exercise when treated with carvedilol.

Effects of carvedilol on oxygen uptake and heart rate kinetics in patients with chronic heart failure at simulated altitude / M. Karsten, M. Contini, C. Cefalù, G. Cattadori, P. Palermo, A. Apostolo, M. Bussotti, D. Magrì, E. Salvioni, S. Farina, S. Sciomer, A.M. Catai, P. Agostoni. - In: EUROPEAN JOURNAL OF PREVENTIVE CARDIOLOGY. - ISSN 2047-4873. - 19:3(2012 Jun), pp. 444-451.

Effects of carvedilol on oxygen uptake and heart rate kinetics in patients with chronic heart failure at simulated altitude

S. Farina;P. Agostoni
Ultimo
2012-06

Abstract

Background: The response to moderate exercise at altitude in heart failure (HF) is unknown. Methods and results: We evaluated 30 HF patients, (NYHA I-III, 25 M/5 F; 59 ± 10 years; LVEF = 39.6 ± 7.1%), in stable clinical conditions, treated with carvedilol at the maximal tolerated dose. We performed a maximal cardiopulmonary exercise test (CPET) with ramp protocol at sea level to evaluate patients' performance and two moderate intensity constant workload CPETs (50% of peak workload) at sea level (normoxia) and simulated altitude (hypoxia). Oxygen uptake ( $${\stackrel{\cdot }{\hbox{ V }}\hbox{ O }}_{2}$$ ) and heart rate (HR) on-kinetics at constant workload were assessed calculating the time constant (τ) with a monoexponential equation. $${\stackrel{\cdot }{\hbox{ V }}\hbox{ O }}_{2}$$ and HR were higher in hypoxia (0.944 ± 0.233 vs 1.031 ± 0.264 l/min; 100 ± 23 vs 108 ± 22 bpm; p < 0.001). On-kinetics showed a different behavior of τ being $${\stackrel{\cdot }{\hbox{ V }}\hbox{ O }}_{2}$$ faster in hypoxia (67.1 ± 23.0 vs. 56.3 ± 19.7 s; p = 0.026) and HR faster in normoxia (49.3 ± 19.4 vs. 62.2 ± 22.5 s; p = 0.018). Ten patients, who lowered oxygen kinetics in hypoxia, had greater HR increase during maximal CPET suggesting lower functional betablockade. The higher τ of $${\stackrel{\cdot }{\hbox{ V }}\hbox{ O }}_{2}$$ in hypoxia is likely to be due to a peripheral effect of carvedilol mediated either by β- or α-receptor. Conclusion: HF patients performing moderate exercise at 2000 m simulated altitude have 20% $${\stackrel{\cdot }{\hbox{ V }}\hbox{ O }}_{2}$$ increase without trouble at the beginning of exercise when treated with carvedilol.
Settore MED/11 - Malattie dell'Apparato Cardiovascolare
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/2434/177934
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