Peripheral muscle dysfunction in idiopathic pulmonary arterial hypertension

Area of Science:

• Pulmonary Hypertension
• Muscle Physiology
• Exercise Intolerance

Background:

• Idiopathic pulmonary arterial hypertension (IPAH) often leads to persistent exercise intolerance, even with advanced therapies.
• The role of peripheral muscle dysfunction in IPAH-related exercise limitation is not well understood.
• This study investigated muscle weakness and morphological changes in IPAH patients.

Purpose of the Study:

• To characterize quadriceps muscle function, morphology, and enzymatic profile in IPAH patients.
• To compare these characteristics with age-matched healthy controls.
• To determine the correlation between muscle changes and exercise capacity in IPAH.

Main Methods:

• Compared 10 IPAH patients with 10 controls.
• Assessed exercise capacity, thigh muscle cross-sectional area (CT scan), and quadriceps strength (maximal voluntary contraction and twitch response).
• Analyzed quadriceps muscle biopsy for fiber type, morphology, and enzymatic profile.

Main Results:

• IPAH patients showed lower type I muscle fibers, reduced maximal voluntary contraction and quadriceps twitch, and an increased phosphofructokinase/3-hydroxyacyl-CoA-dehydrogenase ratio.
• Thigh muscle cross-sectional area tended to be lower in IPAH patients.
• Maximal oxygen uptake correlated with quadriceps strength; anaerobic threshold correlated with oxidative enzyme levels and type I fiber capillarity.

Conclusions:

• IPAH patients exhibit significant peripheral muscle abnormalities.
• These muscle changes are partly associated with reduced exercise capacity.
• Peripheral muscle dysfunction is a key factor in IPAH-related exercise intolerance.