A practical approach to assess leg muscle oxygenation during ramp-incremental cycle ergometry in heart failure

• Main Author: Barroco, Adriano Candido [UNIFESP]
• Publication Date: 2017
• Other Authors: Sperandio, Priscila Abreu [UNIFESP], Reis, Michel Silva, Almeida, Dirceu Rodrigues de [UNIFESP], Neder, Jose Alberto [UNIFESP]
• Format: Article
• Language: eng
• Source: Repositório Institucional da UNIFESP
• Download full: https://dx.doi.org/10.1590/1414-431X20176327; https://repositorio.unifesp.br/handle/11600/55457
• topic: Heart failure; Exercise; Oxygen; Muscle; Near-infrared spectroscopy

Heart failure is characterized by the inability of the cardiovascular system to maintain oxygen (O2) delivery (i.e., muscle blood flow in non-hypoxemic patients) to meet O2 demands. The resulting increase in fractional O2 extraction can be non-invasively tracked by deoxygenated hemoglobin concentration (deoxi-Hb) as measured by near-infrared spectroscopy (NIRS). We aimed to establish a simplified approach to extract deoxi-Hb-based indices of impaired muscle O2 delivery during rapidly-incrementing exercise in heart failure. We continuously probed the right vastus lateralis muscle with continuous-wave NIRS during a rampincremental cardiopulmonary exercise test in 10 patients (left ventricular ejection fraction o35%) and 10 age-matched healthy males. Deoxi-Hb is reported as % of total response (onset to peak exercise) in relation to work rate. Patients showed lower maximum exercise capacity and O2 uptake-work rate than controls (Po0.05). The deoxi-Hb response profile as a function of work rate was S-shaped in all subjects, i.e., it presented three distinct phases. Increased muscle deoxygenation in patients compared to controls was demonstrated by: i) a steeper mid-exercise deoxi-Hb-work rate slope (2.2±1.3 vs 1.0±0.3% peak/W, respectively; Po0.05), and ii) late-exercise increase in deoxi-Hb, which contrasted with stable or decreasing deoxi-Hb in all controls. Steeper deoxi-Hb-work rate slope was associated with lower peak work rate in patients (r=–0.73; P=0.01). This simplified approach to deoxi-Hb interpretation might prove useful in clinical settings to quantify impairments in O2 delivery by NIRS during ramp-incremental exercise in individual heart failure patients.