Document Detail

Effect of betaxolol on the hemodynamic, gas exchange, and cardiac output response to exercise in chronic atrial fibrillation.
MedLine Citation:
PMID:  10208225     Owner:  NLM     Status:  MEDLINE    
BACKGROUND: beta-blockade controls the ventricular response to exercise in chronic atrial fibrillation (AF), but the effects of beta-blockers on exercise capacity in AF have been debated. METHODS: Twelve men with AF (65+/-8 years) participated in a randomized, double-blind, placebo-controlled study of betaxolol (20 mg daily). Patients underwent maximal exercise testing with ventilatory gas exchange analysis, and a separate, submaximal test (50% of maximum) during which cardiac output was measured by a CO2 rebreathing technique. RESULTS: After betaxolol therapy, heart rate was reduced both at rest (92+/-27 vs 62+/-12 beats/min; p < 0.001) and at peak exercise (173+/-22 vs 116+/-24 beats/min; p < 0.001). Maximal oxygen uptake (VO2) was reduced by 19% after betaxolol (21.8+/-5.3 with placebo vs 17.6+/-5.1 mL/kg/min with betaxolol; p < 0.05), with similar reductions observed for maximal exercise time, minute ventilation, and CO2 production. VO2 was reduced by a similar extent (19%) at the ventilatory threshold. Submaximal cardiac output was reduced by 15% during betaxolol therapy (12.9+/-2.3 vs 10.9+/-1.3 L/min; p < 0.05), and stroke volume was higher (88.0+/-21 vs 105.6+/-19 mL/beat; p < 0.05). CONCLUSION: Betaxolol therapy in patients with AF effectively controlled the ventricular rate at rest and during exercise, but also caused considerable reductions in maximal VO2 and cardiac output during exercise. The observed increase in stroke volume could not adequately compensate for reduced heart rate to maintain VO2 during exercise.
J E Atwood; J Myers; S Quaglietti; J Grumet; R Gianrossi; T Umman
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Publication Detail:
Type:  Clinical Trial; Journal Article; Randomized Controlled Trial    
Journal Detail:
Title:  Chest     Volume:  115     ISSN:  0012-3692     ISO Abbreviation:  Chest     Publication Date:  1999 Apr 
Date Detail:
Created Date:  1999-05-06     Completed Date:  1999-05-06     Revised Date:  2007-11-15    
Medline Journal Info:
Nlm Unique ID:  0231335     Medline TA:  Chest     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  1175-80     Citation Subset:  AIM; IM    
Cardiology Division, Palo Alto Veterans Affairs Health Care System and Stanford University, CA 94304, USA.
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MeSH Terms
Adrenergic beta-Antagonists / therapeutic use*
Atrial Fibrillation / drug therapy,  physiopathology*
Betaxolol / therapeutic use*
Cardiac Output / drug effects
Chronic Disease
Cross-Over Studies
Double-Blind Method
Exercise Test*
Exercise Tolerance
Heart Rate / drug effects
Hemodynamics / drug effects*
Middle Aged
Pulmonary Gas Exchange / drug effects*
Stroke Volume / drug effects
Reg. No./Substance:
0/Adrenergic beta-Antagonists; 63659-18-7/Betaxolol

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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