title: Effects of carvedilol on oxygen uptake and heart rate kinetics in patients with chronic heart failure at simulated altitude.
abstract: BACKGROUND
  The response to moderate exercise at altitude in heart failure (HF) is unknown.
  
  
  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 (.VO2 ) and heart rate (HR) on-kinetics at constant workload were assessed calculating the time constant (τ) with a monoexponential equation. .VO2 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 .VO2 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 beta-blockade. The higher τ of .VO2 in hypoxia is likely to be due to a peripheral effect of carvedilol mediated either by β- or α-receptor.
  
  
  CONCLUSIONS
  HF patients performing moderate exercise at 2000 m simulated altitude have 20% .VO2 increase without trouble at the beginning of exercise when treated with carvedilol.
authors: Centro Cardiologico Monzino, IRCCS, Università di Milano, Via Parea 4, Milan, Italy.
authors: Marlus
authors: M
authors: Karsten
authors: Mauro
authors: M
authors: Contini
authors: Claudia
authors: C
authors: Cefalù
authors: Gaia
authors: G
authors: Cattadori
authors: Pietro
authors: P
authors: Palermo
authors: Anna
authors: A
authors: Apostolo
authors: Maurizio
authors: M
authors: Bussotti
authors: Damiano
authors: D
authors: Magrì
authors: Elisabetta
authors: E
authors: Salvioni
authors: Stefania
authors: S
authors: Farina
authors: Susanna
authors: S
authors: Sciomer
authors: Aparecida Maria
authors: AM
authors: Catai
authors: Piergiuseppe
authors: P
authors: Agostoni
mesh_terms: D018674:Adrenergic Antagonists / Q000627:therapeutic use*; D000368:Aged; D000531:Altitude; D002227:Carbazoles / Q000627:therapeutic use*; D000077261:Carvedilol; D002908:Chronic Disease; D005080:Exercise Test; D005260:Female; D006333:Heart Failure / Q000175:diagnosis / Q000188:drug therapy* / Q000378:metabolism / Q000503:physiopathology; D006339:Heart Rate / Q000187:drug effects*; D006801:Humans; D000860:Hypoxia / Q000378:metabolism / Q000503:physiopathology*; D007700:Kinetics; D008297:Male; D008875:Middle Aged; D009206:Myocardium / Q000378:metabolism*; D010101:Oxygen Consumption / Q000187:drug effects*; D011412:Propanolamines / Q000627:therapeutic use*; D016896:Treatment Outcome
chemical_list: D018674:Adrenergic Antagonists; D002227:Carbazoles; D011412:Propanolamines; D000077261:Carvedilol