title: Heart rate dynamics during a treadmill cardiopulmonary exercise test in optimized beta-blocked heart failure patients.
abstract: BACKGROUND
  Calculating the maximum heart rate for age is one method to characterize the maximum effort of an individual. Although this method is commonly used, little is known about heart rate dynamics in optimized beta-blocked heart failure patients.
  
  
  OBJECTIVE
  The aim of this study was to evaluate heart rate dynamics (basal, peak and % heart rate increase) in optimized beta-blocked heart failure patients compared to sedentary, normal individuals (controls) during a treadmill cardiopulmonary exercise test.
  
  
  METHODS
  Twenty-five heart failure patients (49+/-11 years, 76% male), with an average LVEF of 30+/-7%, and fourteen controls were included in the study. Patients with atrial fibrillation, a pacemaker or noncardiovascular functional limitations or whose drug therapy was not optimized were excluded. Optimization was considered to be 50 mg/day or more of carvedilol, with a basal heart rate between 50 to 60 bpm that was maintained for 3 months.
  
  
  RESULTS
  Basal heart rate was lower in heart failure patients (57+/-3 bpm) compared to controls (89+/-14 bpm; p<0.0001). Similarly, the peak heart rate (% maximum predicted for age) was lower in HF patients (65.4+/-11.1%) compared to controls (98.6+/-2.2; p<0.0001). Maximum respiratory exchange ratio did not differ between the groups (1.2+/-0.5 for controls and 1.15+/-1 for heart failure patients; p=0.42). All controls reached the maximum heart rate for their age, while no patients in the heart failure group reached the maximum. Moreover, the % increase of heart rate from rest to peak exercise between heart failure (48+/-9%) and control (53+/-8%) was not different (p=0.157).
  
  
  CONCLUSIONS
  No patient in the heart failure group reached the maximum heart rate for their age during a treadmill cardiopulmonary exercise test, despite the fact that the percentage increase of heart rate was similar to sedentary normal subjects. A heart rate increase in optimized beta-blocked heart failure patients during cardiopulmonary exercise test over 65% of the maximum age-adjusted value should be considered an effort near the maximum. This information may be useful in rehabilitation programs and ischemic tests, although further studies are required.
authors: Laboratório de Insuficiência Cardíaca e Transplante, Instituto do Coração, Faculdade de Medicina, Universidade de São Paulo, São Paulo, SP, Brazil. vitor.carvalho@usp.br
authors: Vitor Oliveira
authors: VO
authors: Carvalho
authors: Guilherme Veiga
authors: GV
authors: Guimarães
authors: Emmanuel Gomes
authors: EG
authors: Ciolac
authors: Edimar Alcides
authors: EA
authors: Bocchi
mesh_terms: D000319:Adrenergic beta-Antagonists / Q000627:therapeutic use*; D000328:Adult; D002227:Carbazoles / Q000627:therapeutic use*; D000077261:Carvedilol; D016022:Case-Control Studies; D005080:Exercise Test / Q000187:drug effects*; D017079:Exercise Tolerance / Q000187:drug effects; D005260:Female; D006333:Heart Failure / Q000188:drug therapy* / Q000503:physiopathology; D006339:Heart Rate / Q000187:drug effects*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010101:Oxygen Consumption / Q000187:drug effects; D011412:Propanolamines / Q000627:therapeutic use*; D011659:Pulmonary Gas Exchange / Q000187:drug effects; D016896:Treatment Outcome
chemical_list: D000319:Adrenergic beta-Antagonists; D002227:Carbazoles; D011412:Propanolamines; D000077261:Carvedilol