title: Effects of respiratory exchange ratio on the prognostic value of peak oxygen consumption and ventilatory efficiency in patients with systolic heart failure.
abstract: OBJECTIVE
  The purpose of this analysis was to evaluate the prognostic characteristics of peak oxygen consumption (Vo2) and the minute ventilation/carbon dioxide (VE/Vco2) slope of different peak respiratory exchange ratios (RERs) obtained from cardiopulmonary exercise testing in patients with heart failure (HF).
  
  
  BACKGROUND
  For patients with HF, peak Vo2 and the VE/Vco2 slope are used for assessing prognosis. Peak Vo2 is assessed in association with peak RER ≥1.10, indicating maximal effort and prognostic sensitivity. Conversely, the VE/Vco2 slope provides effort-independent prognostic discrimination.
  
  
  METHODS
  Patients with HF scheduled to undergo cardiopulmonary exercise testing were enrolled. Patients were subclassified by peak RER (RER <1.00, RER 1.00 to 1.04, RER 1.05 to 1.09, RER ≥1.10) and followed for up to 3 years for major cardiac-related events (death, left ventricular assist device implantation, or cardiac transplantation).
  
  
  RESULTS
  Included were 1,728 patients with HF (75% males; 40% ischemic etiology; age: 55 ± 14 years; left ventricular ejection fraction: 28 ± 10%). Two hundred seventy major events occurred, with no proportional differences across the RER subgroups. Multivariate Cox regression analysis indicated that the VE/Vco2 slope and peak Vo2 remained prognostic within each subgroup; the VE/Vco2 slope remained the strongest predictor. Receiver-operating characteristic analysis demonstrated equitable prognostic cutoffs for the VE/Vco2 slope (range: 34.9 to 35.7; area under the curve [AUC] range: 0.69 to 0.75) and peak Vo2 (range: 13.8 to 14.0 ml·kg(-1)·min(-1); AUC range: 0.68 to 0.75).
  
  
  CONCLUSIONS
  Peak Vo2 provided a sensitive assessment of prognosis in patients with HF in all RER subgroups. The VE/Vco2 slope provided greater prognostic discrimination in all RER subgroups. Clinical consideration may be warranted for patients with low RER, low peak Vo2, and an elevated VE/Vco2 slope.
authors.affiliation: LeBauer Cardiovascular Research Foundation, Greensboro, North Carolina; Department of Kinesiology, University of North Carolina at Greensboro, Greensboro, North Carolina. Electronic address: Paul.Chase@conehealth.com.
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Chase
authors.affiliation: LeBauer Cardiovascular Research Foundation, Greensboro, North Carolina; Department of Kinesiology, University of North Carolina at Greensboro, Greensboro, North Carolina.
authors.forename: Aarti
authors.initials: A
authors.lastname: Kenjale
authors.affiliation: Department of Physical Therapy, Leonard M. Miller School of Medicine, University of Miami, Miami, Florida.
authors.forename: Lawrence P
authors.initials: LP
authors.lastname: Cahalin
authors.affiliation: Department of Physical Therapy, College of Applied Health Sciences, University of Illinois Chicago, Chicago, Illinois.
authors.forename: Ross
authors.initials: R
authors.lastname: Arena
authors.affiliation: Department of Kinesiology, University of North Carolina at Greensboro, Greensboro, North Carolina.
authors.forename: Paul G
authors.initials: PG
authors.lastname: Davis
authors.affiliation: Division of Cardiology, Veterans Affairs Palo Alto Health Care System, Stanford University, Palo Alto, California.
authors.forename: Jonathan
authors.initials: J
authors.lastname: Myers
authors.affiliation: Cardiology, IRCCS Policlinico San Donato, University of Milano, San Donato Milanese, Milan, Italy.
authors.forename: Marco
authors.initials: M
authors.lastname: Guazzi
authors.affiliation: Division of Cardiovascular Medicine, Brigham and Women's Hospital, Boston, Massachusetts.
authors.forename: Daniel E
authors.initials: DE
authors.lastname: Forman
authors.affiliation: Cardiovascular Medicine, Stanford University, Palo Alto, California.
authors.forename: Euan
authors.initials: E
authors.lastname: Ashley
authors.affiliation: Department of Internal Medicine, Virginia Commonwealth University, Richmond, Virginia.
authors.forename: Mary Ann
authors.initials: MA
authors.lastname: Peberdy
authors.affiliation: Division of Cardiovascular Medicine, Brigham and Women's Hospital, Boston, Massachusetts.
authors.forename: Erin
authors.initials: E
authors.lastname: West
authors.affiliation: LeBauer Cardiovascular Research Foundation, Greensboro, North Carolina.
authors.forename: Christopher T
authors.initials: CT
authors.lastname: Kelly
authors.affiliation: LeBauer Cardiovascular Research Foundation, Greensboro, North Carolina.
authors.forename: Daniel R
authors.initials: DR
authors.lastname: Bensimhon
mesh_terms: D005080:Exercise Test; D005260:Female; D054143:Heart Failure, Systolic / Q000378:metabolism* / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010101:Oxygen Consumption; D011379:Prognosis; D011659:Pulmonary Gas Exchange; D012123:Pulmonary Ventilation
keywords: cardiopulmonary exercise test; heart failure; respiratory exchange ratio