Skeletal muscle dysfunction in patients with idiopathic pulmonary arterial hypertension

Dyspnea and exercise limitation are common in patients with idiopathic pulmonary arterial hypertension (IPAH). Recently, a reduction in inspiratory and expiratory muscle strength has been observed in IPAH. However, it has not been investigated whether this respiratory muscle weakness might be part of a general muscle dysfunction as observed in congestive left heart failure. Therefore, in 24 consecutive IPAH patients (16 female; age 58.7+/-16.2; WHO class II-III; systolic pulmonary artery pressure during echocardiography at rest (sPAP) 65.0+/-20.6 mmHg, and 6-min-walk test (6-MWT) 473.6+/-127.7 m), the maximal isometric forearm muscle strength (best of three hand grip manoeuvres), maximal inspiratory and expiratory mouth occlusion pressures (Pimax, Pemax) were prospectively evaluated. The isometric forearm muscle strength was significantly lower in IPAH patients (281.7+/-102.6N) than in matched 24 healthy controls (397.1+/-116.8 N; p=0.03). In IPAH patients, there was a correlation between maximal isometric forearm muscle strength and 6-MWT (r=0.67; p=0.0007) and both, Pimax (r=0.69; p=0.0003) and Pemax (r=0.63; p=0.01), respectively. There was no correlation between forearm muscle strength and sPAP (r=0.30; p=0.16). The present skeletal muscle dysfunction is a novel finding in patients with IPAH. The correlation with respiratory muscle dysfunction and severity of disease might indicate a generalised "myopathy" in IPAH.