['Ventilatory 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.', 'A 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 slope(50) or OUES(50)) and 100% (VE/VCO2 slope(100) or OUES(100)) 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: > or = 0.74, P < .001). Area under the ROC curve for the VE/VCO2 slope(100) was, however, significantly greater than OUES(50), OUES(100), and peak VO2 (P < .05).'] Is the minute ventilation/carbon dioxide production slope prognostically superior to the oxygen uptake efficiency slope?