The oxygen uptake efficiency slope is reduced in older patients with heart failure and a normal ejection fraction

Abstract

The oxygen uptake efficiency slope (OUES) response has not been characterized in heart failure (HF) patients with a normal ejection fraction (NEF). Fifty-nine subjects with systolic HF, 59 with HF-NEF and 28 healthy age-matched controls participated in this analysis. The OUES (systolic HF: 1.23 ± 0.41 vs. HF-NEF: 1.22 ± 0.30 vs. controls: 1.51 ± 0.49) was significantly reduced in both HF groups compared to controls (p < 0.001). Compared to healthy controls, the OUES is reduced in HF-NEF patients to a similar degree as those with systolic HF. Thus, as in systolic HF, the OUES may provide clinically useful information in patients with HF-NEF.

Introduction

The diagnostic and prognostic value of cardiopulmonary exercise testing (CPX) in patients with systolic heart failure (HF) is supported by a robust body of evidence [1]. There is, however, a paucity of information regarding the clinical utility of CPX in patients diagnosed with HF but presenting with a normal ejection fraction (NEF). One investigation has found the minute ventilation/carbon dioxide production (VE/VCO₂) slope, but not peak oxygen consumption (VO₂), retains prognostic value in patients with HF-NEF in a multivariate regression analysis [2]. While the VE/VCO₂ slope and peak VO₂ are the most prominent CPX variables in present day research investigations and clinical practice, other measures have demonstrated potential value. The oxygen uptake efficiency slope (OUES) is one such measure, which is purported to reflect the integration of pulmonary, cardiovascular, and skeletal muscle function during exercise [3]. Previous research examining the prognostic value of the OUES is presently equivocal. Davies et al. [4] found the OUES was prognostically superior to both peak VO₂ and the VE/VCO₂ slope. Arena et al. [5] conversely reported the VE/VCO₂ slope was the superior prognostic marker compared to the OUES. Both of these investigations included cohorts that were exclusively [4] or predominantly [5] diagnosed with systolic HF.

Similar to Guazzi et al. [2], our group has found the VE/VCO₂ slope is significantly lower in patients with HF-NEF compared to those with systolic HF. [6] Conversely, peak VO₂ was similarly diminished, and significantly lower in both HF-NEF and systolic HF groups compared to apparently healthy controls.

Because little is known about OUES in the key population of older persons with HF-NEF, the primary purpose of this analysis was to compare the characteristics of the OUES in older HF subjects and specifically in those with HF-NEF as compared to systolic HF and healthy age-matched subjects.