title: Systolic blood pressure influences the interpretation of cardiopulmonary exercise tests and helps identify a very high-risk cohort of heart failure patients.
abstract: BACKGROUND
  Ventilatory inefficiency (high volume of expired air/volume of carbon dioxide eliminated [Ve/Vco2] slope), and impaired exercise tolerance (low peak volume of oxygen consumption) obtained from cardiopulmonary exercise testing (CPX) strongly predict mortality in heart failure (HF) patients; however, other CPX variables may also contain prognostic information. Therefore, the purpose of this study was to determine the prognostic power of the aggregate of CPX data.
  
  
  METHODS
  The study prospectively monitored 390 patients referred for cardiac transplantation evaluation for 10 years for events (death, urgent transplant, left ventricular assist devices). Cox regression was used to analyze 18 CPX variables to identify the best survival model.
  
  
  RESULTS
  Ve/Vco2 slope was the most powerful mortality predictor, and only resting systolic blood pressure (SBP) added additional independent prognostic power when expressed at its threshold effect value as SBP ≤ 100 mm Hg. Patients with low SBP had a greater risk than those who were within the next higher quartile of Ve/Vco2 slope with SBP > 100 mm Hg. A very high-risk cohort included 9% of the population that had a Ve/Vco2 slope > 41 and SBP ≤ 100 mm Hg and an associated 2-year event rate of 67%; conversely, a low-risk cohort had a Ve/Vco2 slope ≤ 30 and SBP >100 mm Hg and associated 2-, 5-, and 10-year event rates of 5%, 12%, and 30%, respectively.
  
  
  CONCLUSIONS
  Ve/Vco2 slope was the best individual predictive CPX variable and its interpretation was significantly altered by the presence of hypotension. An algorithm combining these CPX variables identifies a HF population at very high risk of early death and warranting advanced therapies.
authors.affiliation: Division of Cardiovascular Medicine, University of Michigan, Ann Arbor, Michigan. Electronic address: bbard@umich.edu.
authors.forename: Robert L
authors.initials: RL
authors.lastname: Bard
authors.affiliation: Center for Statistical Consultation and Research, University of Michigan, Ann Arbor, Michigan.
authors.forename: Brenda W
authors.initials: BW
authors.lastname: Gillespie
authors.affiliation: Division of Cardiovascular Medicine, University of Michigan, Ann Arbor, Michigan.
authors.forename: David C
authors.initials: DC
authors.lastname: Lange
authors.affiliation: Division of Cardiovascular Medicine, University of Michigan, Ann Arbor, Michigan.
authors.forename: Agnes
authors.initials: A
authors.lastname: Pinter
authors.affiliation: Division of Cardiovascular Medicine, University of Michigan, Ann Arbor, Michigan.
authors.forename: John M
authors.initials: JM
authors.lastname: Nicklas
mesh_terms: D000328:Adult; D000368:Aged; D001794:Blood Pressure / Q000502:physiology*; D015331:Cohort Studies; D005080:Exercise Test; D005260:Female; D006333:Heart Failure / Q000175:diagnosis* / Q000503:physiopathology* / Q000601:surgery; D016027:Heart Transplantation; D006353:Heart-Assist Devices; D006801:Humans; D008176:Lung Volume Measurements; D008297:Male; D008875:Middle Aged; D010101:Oxygen Consumption / Q000502:physiology; D011237:Predictive Value of Tests; D011379:Prognosis; D011446:Prospective Studies; D011659:Pulmonary Gas Exchange / Q000502:physiology; D018570:Risk Assessment
keywords: cardiopulmonary exercise testing; heart failure; hypotension; ventilatory inefficiency