Effects of a Rehabilitation Program on Skeletal Muscle Function in Idiopathic Pulmonary Arterial Hypertension

INTRODUCTION: A majority of patients with idiopathic pulmonary arterial hypertension (IPAH) display persistent exercise intolerance despite current therapies. Whether a rehabilitation program elicits favorable changes in muscle function which would partly explain improvements in exercise tolerance of IPAH patients remains unknown. We performed this study to assess the effect of a 12-week rehabilitation program on skeletal muscle characteristics and exercise tolerance in patients with IPAH. METHODS: Exercise capacity measured by the 6-minute walk test and by the cycle endurance test (CET), limb muscle cross-sectional area, quadriceps function by maximal voluntary contraction and magnetic stimulation (potentiated twitches), and molecular muscle characteristics by quadriceps biopsy of 5 IPAH patients were assessed before and after a 12-week rehabilitation program. RESULTS: Following training, improvements in all patients were observed for the 6-minute walk test distance, from 441 (75) to 499 (85) m, P = .01, and the CET time, from 429 (239) to 633 (380) seconds, P = .16. Minute ventilation assessed at isotime during CET decreased by 15(11)%, P = .05. This was related to both decreased carbon dioxide output and (V) over dot(E)/(V) over dot(CO2). These improvements were associated with decreased type IIx fiber proportion, 31(8)% to 23(10)%, P = .05. DISCUSSION: Peripheral muscle characteristic improvements may contribute to the clinical benefit observed following a rehabilitation program in IPAH.