title: Prognostic ability of VE/VCO2 slope calculations using different exercise test time intervals in subjects with heart failure.
abstract: BACKGROUND
  The minute ventilation-carbon dioxide production (VE/VCO2) slope, obtained during exercise testing, possesses prognostic value in heart failure (HF). The VE-VCO2 relationship is generally linear thereby hypothetically producing similar slope values regardless of the exercise-test time interval used for calculation.
  
  
  METHODS
  This study assesses the ability of the VE/VCO2 slope, calculated at different time intervals throughout a progressive exercise test, to predict 1-year cardiac-related hospitalization and mortality in subjects with HF.
  
  
  METHODS
  Seventy-two subjects underwent symptom-limited exercise testing with ventilatory expired gas analysis. Mean age and left ventricular ejection fraction for 44 male and 28 female subjects were 51.2 years (+/-13.0) and 27.0% (+/-12.3) respectively. The VE/VCO2 slope was calculated from time 0 to 25, 50, 75 and 100% of exercise time and subsequently used to create five randomly selected VE/VCO2 slope categories.
  
  
  RESULTS
  (The intraclass correlation coefficient found calculation of the VE/VCO2 slope, when divided into quartiles, to be a reliable measure (alpha=0.94, P<0.0001). Univariate Cox regression analysis revealed all VE/VCO2 slope categories (25-100% and random selections) were significant predictors of cardiac-related hospitalization and mortality over a 1-year period. Multivariate Cox regression analysis revealed all VE/VCO2 slope categories outperformed peak oxygen consumption (VO2) in predicting hospitalization and mortality at 1 year.
  
  
  CONCLUSIONS
  Although the different classification schemes were not identical, these results suggest VE/VCO2 slope maintains prognostic significance regardless of exercise-test time interval. Calculation of VE/VCO2 slope may therefore still be valuable in subjects putting forth a sub-maximal effort while effort-dependent measures, such as peak VO2, are not.
authors.affiliation: Department of Physical Therapy, Virginia Commonwealth University, Health Sciences Campus, Richmond, Virginia 23298-0224, USA. raarena@mail2.vcu.edu
authors.forename: Ross
authors.initials: R
authors.lastname: Arena
authors.forename: Reed
authors.initials: R
authors.lastname: Humphrey
authors.forename: Mary Ann
authors.initials: MA
authors.lastname: Peberdy
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002245:Carbon Dioxide / Q000378:metabolism*; D005080:Exercise Test; D005260:Female; D006333:Heart Failure / Q000378:metabolism* / Q000401:mortality / Q000503:physiopathology*; D006760:Hospitalization; D006801:Humans; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D010101:Oxygen Consumption / Q000502:physiology; D011237:Predictive Value of Tests; D011379:Prognosis; D011659:Pulmonary Gas Exchange / Q000502:physiology; D012123:Pulmonary Ventilation / Q000502:physiology*
chemical_list: D002245:Carbon Dioxide