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

Authors

  • Bruno Grassi MD, PhD,

    Corresponding author
    1. Department of Science and Biomedical Technologies, University of Milan, LITA–Via Fratelli Cervi 93, I-20090 Segrate (MI), Italy
    2. Institute of Bioimaging and Molecular Physiology, CNR, Segrate (MI), Italy
    • Department of Science and Biomedical Technologies, University of Milan, LITA–Via Fratelli Cervi 93, I-20090 Segrate (MI), Italy
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  • Mauro Marzorati MD, PhD,

    1. Institute of Bioimaging and Molecular Physiology, CNR, Segrate (MI), Italy
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  • Francesca Lanfranconi MD,

    1. Department of Science and Biomedical Technologies, University of Milan, LITA–Via Fratelli Cervi 93, I-20090 Segrate (MI), Italy
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  • Alessandra Ferri PhD,

    1. Department of Science and Biomedical Technologies, University of Milan, LITA–Via Fratelli Cervi 93, I-20090 Segrate (MI), Italy
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  • Miriam Longaretti MS,

    1. Department of Science and Biomedical Technologies, University of Milan, LITA–Via Fratelli Cervi 93, I-20090 Segrate (MI), Italy
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  • Andrea Stucchi MD,

    1. Department of Science and Biomedical Technologies, University of Milan, LITA–Via Fratelli Cervi 93, I-20090 Segrate (MI), Italy
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  • Paola Vago MS,

    1. Department of Science and Biomedical Technologies, University of Milan, LITA–Via Fratelli Cervi 93, I-20090 Segrate (MI), Italy
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  • Claudio Marconi MD,

    1. Institute of Bioimaging and Molecular Physiology, CNR, Segrate (MI), Italy
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  • Lucia Morandi MD

    1. Department of Neuromuscular Diseases, Neurological Institute Carlo Besta, Milan, Italy
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Abstract

Patients with mitochondrial myopathies (MM) or myophosphorylase deficiency (McArdle's disease, McA) show impaired capacity for O2 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 O2 uptake (V̇O2) 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 O2 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. V̇O2 peak and Δ[deoxy(Hb + Mb)] peak were linearly related (r2 = 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

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