Cardiopulmonary exercise testing in ambulatory children with Duchenne and Becker Muscular Dystrophy: a pilot study

Abstract

Introduction The cardiopulmonary exercise test (CPET) is the gold-standard for exercise capacity and could be of additional value to the physical evaluation of children with muscular dystrophy (MD). Knowledge of response to dynamic exercise in MD is scarce because of safety concerns. The purpose of this study was to compare feasibility of the CPET to the current European recommended standard test protocol for physical performance of children with DMD (six minute walk test, motor performance test and quantative muscle testing). Methods The CPET and the standard test protocol were separately assessed within three weeks in a consecutive sample of children with Duchenne and Becker muscular dystrophy. Test protocols were compared with regards to exercise outcome and feasibility parameters: ‘measurement completion rate’, ‘adverse events’ and ‘acceptability’. Results Nine children with Duchenne (N=3) and Becker (N=6) muscular dystrophy participated in this study. Five children (55%) successfully performed a maximal or symptom-limited exercise test which was slightly less than the standard test protocol (66%). There were no signs of rhabdomyolysis or cardiac events after both visits and muscle pain ratings remained within predefined limits of normal response. The five subjects that successfully performed a CPET showed low values of exercise capacity with cardiac pump and/or vascular limitations. The subjects demonstrated large variability in perceived burden of both test protocols possibly influenced by age and disease severity. Conclusion In children with relative mild impairments, the cardio pulmonary exercise test seems to be a feasible and relevant outcome measure for exercise capacity and cardiovascular limitations. To extend our knowledge of exercise response of children with MD further research should be focused on the pathophysiological mechanisms of cardiovascular limitations and development of safety markers for exercise.