title: Patients with heart failure in the "intermediate range" of peak oxygen uptake: additive value of heart rate recovery and the minute ventilation/carbon dioxide output slope in predicting mortality.
abstract: OBJECTIVE
  While patients with heart failure who achieve a peak oxygen uptake (peak VO2) of 10 mL·kg(-1)·min(-1) or less are often considered for intensive surveillance or intervention, those achieving 14 mL·kg(-1)·min(-1) or more are generally considered to be at lower risk. Among patients in the "intermediate" range of 10.1 to 13.9 mL·kg(-1)·min(-1), optimally stratifying risk remains a challenge.
  
  
  METHODS
  Patients with heart failure (N = 1167) referred for cardiopulmonary exercise testing were observed for 21 ± 13 months. Patients were classified into 3 groups of peak VO2 (≤10, 10.1-13.9, and ≥14 mL·kg(-1)·min(-1)). The ability of heart rate recovery at 1 minute (HRR1) and the minute ventilation/carbon dioxide output (VE/VCO2) slope to complement peak VO2 in predicting cardiovascular mortality were determined.
  
  
  RESULTS
  Peak VO2, HRR1 (<16 beats per minute), and the VE/VCO2 slope (>34) were independent predictors of mortality (hazard ratio 1.6, 95% CI: 1.2-2.29, P = .006; hazard ratio 1.7, 95% CI: 1.1-2.5, P = .008; and hazard ratio 2.4, 95% CI: 1.6-3.4, P < .001, respectively). Compared with those achieving a peak VO2 ≥ 14 mL·kg(-1)·min(-1), patients within the intermediate range with either an abnormal VE/VCO2 slope or HRR1 had a nearly 2-fold higher risk of cardiac mortality. Those with both an abnormal HRR1 and VE/VCO2 slope had a higher mortality risk than those with a peak VO2 ≤ 10 mL·kg(-1)·min(-1). Survival was not different between those with a peak VO2 ≤ 10 mL·kg(-1)·min(-1) and those in the intermediate range with either an abnormal HRR1 or VE/VCO2 slope.
  
  
  CONCLUSIONS
  HRR1 and the VE/VCO2 slope effectively stratify patients with peak VO2 within the intermediate range into distinct groups at high and low risk.
authors.affiliation: Hospital Santa Izabel, Salvador, BA, Brazil.
authors.forename: Luiz Eduardo
authors.initials: LE
authors.lastname: Ritt
authors.forename: Ricardo Brandão
authors.initials: RB
authors.lastname: Oliveira
authors.forename: Jonathan
authors.initials: J
authors.lastname: Myers
authors.forename: Ross
authors.initials: R
authors.lastname: Arena
authors.forename: Mary Ann
authors.initials: MA
authors.lastname: Peberdy
authors.forename: Daniel
authors.initials: D
authors.lastname: Bensimhon
authors.forename: Paul
authors.initials: P
authors.lastname: Chase
authors.forename: Daniel
authors.initials: D
authors.lastname: Forman
authors.forename: Marco
authors.initials: M
authors.lastname: Guazzi
mesh_terms: D001944:Breath Tests; D002245:Carbon Dioxide / Q000032:analysis*; D015444:Exercise / Q000502:physiology; D005080:Exercise Test; D045853:Exhalation / Q000502:physiology; D005260:Female; D006333:Heart Failure / Q000378:metabolism / Q000401:mortality / Q000503:physiopathology*; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000378:metabolism*; D010101:Oxygen Consumption / Q000502:physiology*; D011237:Predictive Value of Tests; D011379:Prognosis; D020127:Recovery of Function; D012121:Respiration, Artificial / Q000379:methods*
chemical_list: D002245:Carbon Dioxide; D010100:Oxygen