Application de la spectroscopie infrarouge (NIRS) dans l’évaluation des adaptations musculaires périphériques chez l’enfant cardiaque

Objective. – The purpose of this work is to study the muscular responses in children with congenital heart disease using near infrared spectroscopy during isometric exercise.Materials and methods. – Twelve healthy children and eight children with congenital heart disease (class II and III NYHA) performed an isometric knee extension on Cybex Norm. For every subject, maximal voluntary contraction (MVC) and endurance time (TE) at 50% of MVC was assessed. The near infrared spectroscopy (NIRS) has been used to assess muscular oxygenation (SmO₂) and of blood volume (VS) during exercise and recovery. Half time recovery of the SmO₂ (1/2 Trec) has been also measured.Results. – Cardiac subjects developed MVC and TE weaker than healthy subjects (MVC: 96.1 ±5.0 vs 125.1 ±6.7 N·m; P <0.01) and (TE: 60.88 ±5.7 vs 116.5 ±8.7 secondes; P <0.001). No significant difference of the SmO₂ and the VS has been noted at rest. The SmO₂ decrease rapidly to reach a plateau at 25% of TE in the healthy subjects, whereas the cardiac subjects reach this plateau at 50% of TE. During recovery, 1/2 Trec is significantly higher in cardiac subjects compared to healthy subjects (26.6 ±1.8 secondes vs 18.9 ±1.9 secondes; respectively, P <0.05).Conclusion. – A decreased muscular performance accompanied with oxygenation and blood volume abnormalities has been found in children with congenital heart diseases. The NIRS is a valuable non-invasive technique for assessment of oxygenation and blood volume during exercise.