title: Effects of cold exposure on submaximal exercise performance and adrenergic activation in patients with congestive heart failure and the effects of beta-adrenergic blockade (carvedilol or metoprolol).
abstract: Patients with congestive heart failure (CHF) exhibit a decrease in maximal exercise capacity in response to a cold environment. The aim of this study was to further investigate the impact of cold exposure on submaximal exercise capacity, systemic adrenergic drive, and the effects of long-term beta-adrenergic blockade on these parameters. Thirty-three patients with CHF, with exercise limited by dyspnea and left ventricular ejection fraction of 26 +/- 4%, were randomized to receive metoprolol or carvedilol for 6 months. The observations were compared with 12 age-matched healthy volunteers. Maximal exercise performance with gas exchange analyses were assessed using a ramp protocol, and endurance capacity was measured using 2 constant-load exercise tests performed randomly at 20 degrees C and -8 degrees C. Healthy volunteers increased their submaximal exercise time by 20% (1,353 +/- 455 [20 degrees C] vs 1,635 +/- 475 seconds [-8 degrees C]; p <0.05), whereas patients with CHF exhibited a 21% decrease in exercise time (1,182 +/- 549 [20 degrees C] vs 931 +/- 524 seconds [-8 degrees C]; p <0.05) at -8 degrees C. Beta blockers increased submaximal exercise duration at 20 degrees C (+261 +/- 617 seconds; p <0.05) and -8 degrees C (+374 +/- 729 seconds; p <0.05). Norepinephrine increased to a greater extent at 4 minutes and at the time of exhaustion (at -8 degrees C) only in patients with CHF. Beta-adrenergic blockade caused no significant decrease in plasma norepinephrine levels. Patients with symptomatic CHF exhibited a significant decrease in submaximal exercise time in response to moderate cold exposure. Beta-blocker therapy with either metoprolol or carvedilol significantly increases submaximal exercise time and attenuates the impact of cold exposure on functional capacity.
authors.affiliation: Research Center, Montreal Heart Institute, Quebec, Canada.
authors.forename: Martine
authors.initials: M
authors.lastname: Blanchet
authors.forename: Anique
authors.initials: A
authors.lastname: Ducharme
authors.forename: Normand
authors.initials: N
authors.lastname: Racine
authors.forename: Jean Lucien
authors.initials: JL
authors.lastname: Rouleau
authors.forename: Jean Claude
authors.initials: JC
authors.lastname: Tardif
authors.forename: Martin
authors.initials: M
authors.lastname: Juneau
authors.forename: Johanne
authors.initials: J
authors.lastname: Marquis
authors.forename: Lucie
authors.initials: L
authors.lastname: Larivée
authors.forename: Anil
authors.initials: A
authors.lastname: Nigam
authors.forename: Anick
authors.initials: A
authors.lastname: Fortier
authors.forename: Michel
authors.initials: M
authors.lastname: White
mesh_terms: D000319:Adrenergic beta-Antagonists / Q000494:pharmacology / Q000627:therapeutic use*; D000368:Aged; D001784:Blood Gas Analysis; D002227:Carbazoles / Q000494:pharmacology / Q000627:therapeutic use*; D000077261:Carvedilol; D016022:Case-Control Studies; D003080:Cold Temperature / Q000009:adverse effects*; D004417:Dyspnea / Q000209:etiology; D005080:Exercise Test / Q000187:drug effects; D017079:Exercise Tolerance / Q000187:drug effects*; D005260:Female; D006333:Heart Failure / Q000150:complications / Q000188:drug therapy* / Q000378:metabolism / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008790:Metoprolol / Q000494:pharmacology / Q000627:therapeutic use*; D008875:Middle Aged; D009638:Norepinephrine / Q000097:blood; D010807:Physical Endurance; D011412:Propanolamines / Q000494:pharmacology / Q000627:therapeutic use*; D011446:Prospective Studies; D011941:Receptors, Adrenergic / Q000187:drug effects* / Q000502:physiology*; D016037:Single-Blind Method; D013318:Stroke Volume / Q000187:drug effects
chemical_list: D000319:Adrenergic beta-Antagonists; D002227:Carbazoles; D011412:Propanolamines; D011941:Receptors, Adrenergic; D000077261:Carvedilol; D008790:Metoprolol; D009638:Norepinephrine