A practical approach to assess leg muscle oxygenation during ramp-incremental cycle ergometry in heart failure
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Data
2017
Autores
Barroco, Adriano Candido [UNIFESP]
Sperandio, Priscila Abreu [UNIFESP]
Reis, Michel Silva
Almeida, Dirceu Rodrigues de [UNIFESP]
Neder, Jose Alberto [UNIFESP]
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Resumo
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.
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Brazilian Journal Of Medical And Biological Research. Sao Paulo, v. 50, n. 12, p. -, 2017.