JACC Heart Fail. 2013 Oct;1(5):427-32. doi: 10.1016/j.jchf.2013.05.008. Epub 2013 Sep 11.

Effects of respiratory exchange ratio on the prognostic value of peak oxygen consumption and ventilatory efficiency in patients with systolic heart failure.

Chase PJ¹, Kenjale A², Cahalin LP³, Arena R⁴, Davis PG⁵, Myers J⁶, Guazzi M⁷, Forman DE⁸, Ashley E⁹, Peberdy MA¹⁰, West E⁸, Kelly CT¹¹, Bensimhon DR¹¹.

Author information

1: 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.
2: LeBauer Cardiovascular Research Foundation, Greensboro, North Carolina; Department of Kinesiology, University of North Carolina at Greensboro, Greensboro, North Carolina.
3: Department of Physical Therapy, Leonard M. Miller School of Medicine, University of Miami, Miami, Florida.
4: Department of Physical Therapy, College of Applied Health Sciences, University of Illinois Chicago, Chicago, Illinois.
5: Department of Kinesiology, University of North Carolina at Greensboro, Greensboro, North Carolina.
6: Division of Cardiology, Veterans Affairs Palo Alto Health Care System, Stanford University, Palo Alto, California.
7: Cardiology, IRCCS Policlinico San Donato, University of Milano, San Donato Milanese, Milan, Italy.
8: Division of Cardiovascular Medicine, Brigham and Women's Hospital, Boston, Massachusetts.
9: Cardiovascular Medicine, Stanford University, Palo Alto, California.
10: Department of Internal Medicine, Virginia Commonwealth University, Richmond, Virginia.
11: LeBauer Cardiovascular Research Foundation, Greensboro, North Carolina.

Abstract

OBJECTIVES:

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.