Intérêt de l’épreuve fonctionnelle d’exercice au cours des myopathies inflammatoires avec atteinte pulmonaire

Abstract

Dyspnoea occurring during inflammatory myopathy associated with interstitial lung disease (ILD) can be ascribed to several physiopathological pathways. The purpose of this study was to analyse cardiopulmonary exercise testing (CPET) abnormalities in these patients in order to precise mechanisms responsible for decreased aerobic capacity.Ten patients (52 +/- 12 years) were diagnosed as having inflammatory myopathy with interstitial lung disease. Exercise dyspnoea was found in 9 patients. All of them had a restrictive pattern associated to and impairment of the transfer factor for carbon monoxide. CPET was performed with a bicycle ergometer using a standard protocol of incremental increasing work load.Two patients had a normal exercise capacity while eight patients had abnormal VO2 associated with hyperventilation, abnormal gas exchange, as well as and abnormal dead space. Five patients also exhibited decreased oxygen pulse (<80% expected value) at peak exercise; 4 out of 5 had persistence of ventilatory reserve. In addition DeltaFC/DeltaVO2 was increased (>50) in 7 cases.CPET provides useful information in the understanding of mechanisms of dyspnoea and might be an effective tool in treatment decision making: in patients with inflammatory myopathy and associated ILD abnormal oxygen pulse may reflect cardiac disorder or muscular abnormalities (inflammatory or steroid myopathy).