title: Beta adrenergic blockade does not improve effort tolerance in patients with mitral stenosis in sinus rhythm.
abstract: OBJECTIVE
  This study was designed to assess the effects of beta-blockade on cardiopulmonary exercise performance in symptomatic patients with tight mitral stenosis in sinus rhythm.
  
  
  BACKGROUND
  The role of beta-blockers in these patients has been controversial and assessment of effort tolerance using treadmill exercise time has produced conflicting results.
  
  
  METHODS
  Nineteen patients with isolated symptomatic (New York Heart Association class II or III) mitral stenosis received a beta-blocker (acebutalol or atenolol) or matching placebo for one week each in a randomized double-blind crossover fashion. Exercise on a treadmill with real time gas exchange analysis was performed six times over 4 weeks in each patient. The test was further repeated once within a week of percutaneous mitral valvotomy.
  
  
  RESULTS
  Heart rate at rest and during peak exercise was significantly lower with beta-blockade compared to control state or placebo treatment. Mean peak oxygen consumption did not differ significantly between treatment groups. When patients were arbitrarily classified into those with (group I, heart rate < or = 130.min-1) and those without (group II, heart rate > or = 131.min-1) adequate beta-blockade, there was a significant difference in peak VO2. The peak VO2 for group I: 14.0 +/- 3.2 vs 17.5 +/- 4.0 ml.min-1.kg-1; peak VO2 for group II: 17.2 +/- 2.4 vs 18.0 +/- 2.4 ml.min-1.kg-1 (beta-blockade vs control state respectively). Treadmill exercise time did not differ between treatment groups. The slope of minute ventilation (MV) and carbon dioxide (CO2) excretion, and instantaneous carbon dioxide ventilatory equivalent (MV/VCO2) was unchanged with beta-blocker therapy indicating no improvement in ventilatory performance.
  
  
  CONCLUSIONS
  Beta-blocker therapy in tight mitral stenosis appears to have no beneficial effect on aerobic capacity, nor does it improve ventilatory performance. Adequate beta-blockade may adversely effect peak oxygen consumption.
authors.affiliation: Department of Cardiology, University of Natal/Wentworth Hospital, Durban, South Africa.
authors.forename: J J
authors.initials: JJ
authors.lastname: Patel
authors.forename: R B
authors.initials: RB
authors.lastname: Dyer
authors.forename: A S
authors.initials: AS
authors.lastname: Mitha
mesh_terms: D000070:Acebutolol / Q000008:administration & dosage / Q000627:therapeutic use*; D000293:Adolescent; D000319:Adrenergic beta-Antagonists / Q000008:administration & dosage / Q000627:therapeutic use*; D000328:Adult; D000704:Analysis of Variance; D001262:Atenolol / Q000008:administration & dosage / Q000627:therapeutic use*; D018592:Cross-Over Studies; D004311:Double-Blind Method; D005080:Exercise Test / Q000187:drug effects; D017079:Exercise Tolerance / Q000187:drug effects*; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D008297:Male; D008875:Middle Aged; D008946:Mitral Valve Stenosis / Q000175:diagnosis / Q000188:drug therapy* / Q000503:physiopathology; D010101:Oxygen Consumption / Q000187:drug effects; D014692:Ventilation-Perfusion Ratio / Q000187:drug effects
chemical_list: D000319:Adrenergic beta-Antagonists; D001262:Atenolol; D000070:Acebutolol