title: The relationship between heart rate reserve and oxygen uptake reserve in heart failure patients on optimized and non-optimized beta-blocker therapy.
abstract: BACKGROUND
  The relationship between the percentage of oxygen consumption reserve and percentage of heart rate reserve in heart failure patients either on non-optimized or off beta-blocker therapy is known to be unreliable. The aim of this study was to evaluate the relationship between the percentage of oxygen consumption reserve and percentage of heart rate reserve in heart failure patients receiving optimized and non-optimized beta-blocker treatment during a treadmill cardiopulmonary exercise test.
  
  
  METHODS
  A total of 27 sedentary heart failure patients (86% male, 50+/-12 years) on optimized beta-blocker therapy with a left ventricle ejection fraction of 33+/-8% and 35 sedentary non-optimized heart failure patients (75% male, 47+/-10 years) with a left ventricle ejection fraction of 30+/-10% underwent the treadmill cardiopulmonary exercise test (Naughton protocol). Resting and peak effort values of both the percentage of oxygen consumption reserve and percentage of heart rate reserve were, by definition, 0 and 100, respectively.
  
  
  RESULTS
  The heart rate slope for the non-optimized group was derived from the points 0.949+/-0.088 (0 intercept) and 1.055+/-0.128 (1 intercept), p<0.0001. The heart rate slope for the optimized group was derived from the points 1.026+/-0.108 (0 intercept) and 1.012+/-0.108 (1 intercept), p=0.47. Regression linear plots for the heart rate slope for each patient in the non-optimized and optimized groups revealed a slope of 0.986 (almost perfect) for the optimized group, but the regression analysis for the non-optimized group was 0.030 (far from perfect, which occurs at 1).
  
  
  CONCLUSIONS
  The relationship between the percentage of oxygen consumption reserve and percentage of heart rate reserve in patients on optimized beta-blocker therapy was reliable, but this relationship was unreliable in non-optimized heart failure patients.
authors.affiliation: Faculdade de Medicina, Instituto do Coração, Hospital das Clínicas, Universidade de São Paulo, São Paulo, Brazil. vitor.carvalho@usp.br
authors.forename: Vitor Oliveira
authors.initials: VO
authors.lastname: Carvalho
authors.forename: Guilherme Veiga
authors.initials: GV
authors.lastname: Guimarães
authors.forename: Edimar Alcides
authors.initials: EA
authors.lastname: Bocchi
mesh_terms: D000319:Adrenergic beta-Antagonists / Q000008:administration & dosage*; D047228:Angiotensin II Type 1 Receptor Blockers / Q000008:administration & dosage; D000806:Angiotensin-Converting Enzyme Inhibitors / Q000008:administration & dosage; D002216:Captopril / Q000008:administration & dosage; D002227:Carbazoles / Q000008:administration & dosage*; D000077261:Carvedilol; D004359:Drug Therapy, Combination; D004656:Enalapril / Q000008:administration & dosage; D005080:Exercise Test / Q000187:drug effects; D005260:Female; D006333:Heart Failure / Q000188:drug therapy* / Q000503:physiopathology; D006339:Heart Rate / Q000187:drug effects* / Q000502:physiology; D006801:Humans; D019808:Losartan / Q000008:administration & dosage; D008297:Male; D008875:Middle Aged; D010101:Oxygen Consumption / Q000187:drug effects* / Q000502:physiology; D011412:Propanolamines / Q000008:administration & dosage*
chemical_list: D000319:Adrenergic beta-Antagonists; D047228:Angiotensin II Type 1 Receptor Blockers; D000806:Angiotensin-Converting Enzyme Inhibitors; D002227:Carbazoles; D011412:Propanolamines; D000077261:Carvedilol; D004656:Enalapril; D002216:Captopril; D019808:Losartan