Impaired oxygen extraction in metabolic myopathies: Detection and quantification by near-infrared spectroscopy

✍ Scribed by Bruno Grassi; Mauro Marzorati; Francesca Lanfranconi; Alessandra Ferri; Miriam Longaretti; Andrea Stucchi; Paola Vago; Claudio Marconi; Lucia Morandi

• Publisher: John Wiley and Sons
• Year: 2007
• Tongue: English
• Weight: 302 KB
• Volume: 35
• Category: Article
• ISSN: 0148-639X
• DOI: 10.1002/mus.20708

✦ Synopsis

Abstract

Patients with mitochondrial myopathies (MM) or myophosphorylase deficiency (McArdle's disease, McA) show impaired capacity for O~2~ extraction, low maximal aerobic power, and reduced exercise tolerance. Non‐invasive tools are needed to quantify the metabolic impairment. Six patients with MM, 6 with McA, 25 with symptoms of metabolic myopathy but negative biopsy (patient‐controls, P‐CTRL) and 20 controls (CTRL) underwent an incremental cycloergometric test. Pulmonary O~2~ uptake (V̇O~2~) and vastus lateralis oxygenation indices (by near‐infrared spectroscopy, NIRS) were determined. Concentration changes of deoxygenated hemoglobin and myoglobin (Δ[deoxy(Hb + Mb)]) were considered an index of O~2~ extraction. Δ[deoxy(Hb + Mb)] peak (percent limb ischemia) was lower in MM (25.3 ± 12.0%) and McA (18.7 ± 7.3) than in P‐CTRL (62.4 ± 3.9) and CTRL (71.3 ± 3.9) subjects. V̇O~2~ peak and Δ[deoxy(Hb + Mb)] peak were linearly related (r^2^ = 0.83). In these patients, NIRS is a tool to detect and quantify non‐invasively the metabolic impairment, which may be useful in the follow‐up of patients and in the assessment of therapies and interventions. Muscle Nerve, 2006