Evaluation Of The Oxygen Uptake Efficiency Slope In Heart Failure

Abstract

Peak Oxygen Uptake Efficiency Slope (OUES) predicts outcome in heart failure (HF). We've shown peak OUES is no different than a value measured using data up to 75% of peak. A shortcoming of this technique is the necessity to perform a maximal test in order to determine 75% of peak. Purpose Determine if OUES, calculated using data up to 75% of maximum, is different than OUES at peak exercise; and determine if these values are reflective of cardiopulmonary reserve. Methods We determined OUES in 338 patients with documented HF and left ventricular dysfunction (EF=22±8%) who were referred for peak VO2 assessment (peak VO2=15.9±5 ml·kg−1·min−1) by the hospital's HF clinic. Continuously collected VO2 and VE data was averaged every 15-sec during symptom-limited testing. Least-squares regression performed to determine OUES. OUES was calculated 1) using all exercise data (peak OUES), 2) using data up to an RER value that remained above 1.0 (OUES-1.0), 3) using data up to the workload approximating 4 METs (OUES-4), and 4) using data up to the workload approximating 2 METs (OUES-2). Mean OUES values were compared with one another for each method of OUES determination within and between Weber classes for each OUES method, using one-way ANOVA with Tukey post-hoc analysis (alpha p < 0.05). Results There was no difference between the various OUES values within a Weber Class, except in Class A where the peak OUES was significantly greater than OUES-2. The table presents between group comparisons within each OUES method. Data is mean±SD. Weber Class Peak OUES OUES-1.0 OUES-4 OUES-2TableConclusions Calculation of OUES using various iterations of submaximal data yields similar values to the OUES calculated using all exercise data. It appears that OUES determined using submaximal data, and specifically using data up to an RER = 1.0 or data up to 4 METs, may be used to discriminate cardiopulmonary reserve as determined by Weber Class.