Metabolic parameters derived from cardiopulmonary stress testing for prediction of prognosis in patients with heart failure: the ochsner experience

Abstract

Cardiopulmonary parameters, particularly peak oxygen consumption, have proven utility in prognostic stratification for patients with heart failure. These have been typically corrected for total body weight as opposed to lean body mass (LBM). For practical purposes, fat consumes virtually no oxygen and receives minimal perfusion. Based on this rationale and on observations from previous studies, several investigations conducted at the Ochsner Clinic Foundation have assessed the prognostic value of metabolic parameters when corrected for LBM. Three studies reviewed in this discussion consistently found greater prognostic value for LBM-corrected parameters, especially peak oxygen consumption and oxygen pulse. These findings lead to a strong recommendation for LBM correction of cardiopulmonary exercise stress test-derived parameters for more accurate prognostic stratification in patients with heart failure, especially in the obese population. Other centers have studied additional parameters such as the ventilation to carbon dioxide production slope, oxygen uptake efficiency slope, and partial pressure of end-tidal carbon dioxide during exercise and rest. In multiple studies, these ventilation-dependent parameters have shown prognostic superiority compared with the standard peak oxygen consumption even when obtained from submaximal exercise data. However, no study to our knowledge has compared these parameters with LBM-adjusted values as described herein. The prognostic validity of cardiopulmonary exercise stress test-derived parameters requires further investigation in patients treated with β-blockers.

Keywords: Anaerobic threshold; cardiopulmonary exercise stress test; congestive heart failure; lean body mass; peak oxygen consumption.

Figure 1. Kaplan-Meier survival curves using both peak oxygen consumption (Vo₂) of 14 mL/kg per minute and peak Vo₂ lean of 19 mL/kg per minute as cutoffs show stronger prognostic value for the fat-adjusted peak Vo₂ by log-rank testing. Reproduced with permission from Osman et al.

Figure 2. Kaplan-Meier survival curves using both anaerobic threshold (AT) of 13 mL/kg per minute and AT lean of 16 mL/kg per minute as cutoffs for predicting event-free survival. Reproduced with permission from Lavie et al.

Figure 3. Kaplan-Meier survival curves using both oxygen (O₂) pulse of 10 mL/beat and O₂ pulse lean of 14 mL/beat as cutoffs for predicting event-free survival. Reproduced with permission from Lavie et al.