Understanding the Effects of Pulmonary Arterial Hypertension on Lean Muscle Mass

In a subset of patients, after obtaining informed consent, patients will be scheduled for an in-person visit with a physical therapist. The subject will have their vital signs checked, blood drawn and then will have the PortaMon device applied to their biceps and their calf muscles. The PortaMon is a wireless NIRS device designed to measure muscle oxygenation non-invasively. It has one channel to measure absolute oxygenated hemoglobin and three channels to measure relative concentrations of oxy-, deoxy-, total hemoglobin concentration changes, and tissue saturation index. Following application and activation of the biosensor and the NIRS device, the physical therapist will demonstrate the exercises to the participant and will observe them performing the exercises. After the conclusion of the session (~1.5 hours), the subject's vital signs will be reassessed and blood drawn. The second study visit will be at Week 12.

Inclusion criteria

• Signed informed consent prior to initiation of any study mandated procedure.
• Diagnosis of PAH belonging to one of the following subgroups of Group 1 PH according to the updated clinical classification [Humbert 2022]

• Idiopathic (IPAH)
• Heritable (HPAH)
• Drugs or toxins induced
• Associated (APAH) with one of the following:

• Connective tissue disease;
• Human immunodeficiency virus (HIV) infection;
• Congenital heart disease; or
• Portopulmonary hypertension
• Diagnosis of PAH within 6 months of enrollment or diagnosis of PAH and on stable therapy for 3 months prior to enrollment
• Documented hemodynamic diagnosis of PAH by right heart catheterization (RHC), prior to enrollment showing:

• mPAP > 20 mmHg; and
• PAWP or LVEDP ≤ 15 mmHg
• PVR > 2 Wood units

Exclusion criteria

• Prior to enrollment, evidence of moderately severe obstructive ventilator defect with:

• FEV1/FVC ≤ 5th percentile; and
• FEV1 z-score < 2.5
• Prior to enrollment, evidence of severe restrictive defect with

• TLC < 5th percentile
• FEV1 z-score < 4
• Prior to enrollment, hospitalization (within 1 week) for decompensated right heart failure
• More than moderate aortic or mitral valve disease
• LVEF < 40% within 1 year of screening
• Pregnancy