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

BackgroundVentilatory efficiency, commonly assessed by the minute ventilation (VE)-carbon dioxide production (VCO2) 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 ResultsA total of 341 subjects were diagnosed with HF participated in this analysis. The VE/VCO2 slope and the OUES were calculated using 50% (VE/VCO2 slope50 or OUES50) and 100% (VE/VCO2 slope100 or OUES100) of the exercise data. Peak oxygen consumption (VO2) 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/VCO2 slope and OUES calculations as well as peak VO2 were statistically significant (all areas under the ROC curve: ≥0.74, P < .001). Area under the ROC curve for the VE/VCO2 slope100 was, however, significantly greater than OUES50, OUES100, and peak VO2 (P < .05).ConclusionsAlthough the OUES was a significant predictor of mortality, the VE/VCO2 slope maintained optimal prognostic value. An elevated VE/VCO2 slope may be the single best indicator of increased risk for adverse events.