The Minute Ventilation/Carbon Dioxide Production Slope is Prognostically Superior to the Oxygen Uptake Efficiency Slope

Abstract

Background Ventilatory efficiency, commonly assessed by the minute ventilation (VE)-carbon dioxide production (VCO 2) slope, has proven to be a strong prognostic marker in the heart failure (HF) population. Recently, the oxygen uptake efficiency slope (OUES) has demonstrated prognostic value, but additional comparisons to established cardiopulmonary exercise test (CPET) variables are required. Methods and Results A total of 341 subjects were diagnosed with HF participated in this analysis. The VE/VCO 2 slope and the OUES were calculated using 50% (VE/VCO 2 slope 50 or OUES 50) and 100% (VE/VCO 2 slope 100 or OUES 100) of the exercise data. Peak oxygen consumption (VO 2) was also determined. There were 47 major cardiac-related events during the 3-year tracking period. Receiver operating characteristic (ROC) curve analysis demonstrated the classification schemes for both VE/VCO 2 slope and OUES calculations as well as peak VO 2 were statistically significant (all areas under the ROC curve: ≥0.74, P < .001). Area under the ROC curve for the VE/VCO 2 slope 100 was, however, significantly greater than OUES 50, OUES 100, and peak VO 2 ( P < .05). Conclusions Although the OUES was a significant predictor of mortality, the VE/VCO 2 slope maintained optimal prognostic value. An elevated VE/VCO 2 slope may be the single best indicator of increased risk for adverse events.