Peripheral muscle dysfunction in idiopathic pulmonary arterial hypertension
- Vincent Mainguy,
- François Maltais,
- Didier Saey,
- Philippe Gagnon,
- Simon Martel,
- Mathieu Simon,
- Steeve Provencher
- Centre de Recherche de l'Institut Universitaire de Cardiologie et de Pneumologie de Québec, Université Laval, Québec, Canada
- Correspondence to Dr Steeve Provencher, Centre de Recherche de l'Institut Universitaire de Cardiologie et de Pneumologie de Québec, Service de Pneumologie, 2725, chemin Sainte-Foy, Québec G1V 4G5, Canada;
- Received 26 March 2009
- Accepted 11 August 2009
- Published Online First 30 August 2009
Background A majority of patients with idiopathic pulmonary arterial hypertension (IPAH) display persistent exercise intolerance despite new specific therapies. Whether patients with IPAH exhibit peripheral muscle dysfunction that may contribute to this limitation remains unknown. The hypothesis that the muscles of patients with IPAH are weaker and display morphological changes compared with those of control subjects and that those changes partly correlate with their exercise capacity was tested.
Objective To characterise quadriceps function, morphology and the enzymatic profile of patients with IPAH.
Methods Exercise capacity, limb muscle cross-sectional area by CT scan, quadriceps strength by maximal voluntary contraction and non-volitional magnetic stimulation of the femoral nerve (quadriceps twitch; TWq), and muscle morphology and enzymatic profile by quadriceps biopsy of 10 patients with IPAH were compared with those of 10 matched controls subjects.
Results Patients with IPAH displayed a lower proportion of type I muscle fibres (p=0.05), a lower maximal voluntary contraction (p=0.05) and TWq (p=0.01), and an increased muscular phosphofructokinase/3-hydroxyacyl-CoA-dehydrogenase ratio (p=0.05). They also tended to have lower thigh muscle cross-sectional area (p=0.15). Maximal oxygen uptake correlated with quadriceps strength (R2=0.42, p=0.04), and oxygen uptake at anaerobic threshold correlated with muscle oxidative capacity assessed by oxidative enzyme level for citrate synthase (R2=0.45, p=0.05) and 3-hydroxyacyl-CoA-dehydrogenase (R2=0.86, p<0.01), and type I fibre capillarity (R2=0.57, p=0.02).
Conclusion Patients with IPAH present significant peripheral muscle changes that partly correlated with their exercise capacity.
See Editorial, p97
Linked articles 120824.
SP is a clinical scientist of the Fonds de Recherche en Santé du Québec and FM is a research scholar of the Fonds de la Recherche en Santé du Québec.
Funding Réseau en Santé Respiratoire du Fonds de Recherche en Santé du Québec and the Groupe de recherche en santé respiratoire de l'Université Laval (GESER).
Competing interests None.
Ethics approval The research protocol was approved by the institutional ethics committee.
Patient consent Obtained.
Provenance and peer review Not commissioned; externally peer reviewed.