The goals of this study were two-fold. First, the attempt to quantify the relationships between pulmonary arterial stiffness, right ventricular function and the efficiency of ventricular-vascular interactions in patients with pulmonary arterial hypertension (PAH). Second, the attempt to quantify the effects of exercise on pulmonary arterial stiffness, pulmonary vascular resistance, right ventricular function and the efficiency of ventricular-vascular interactions in patients with PAH.

The goals of this study are to quantify right ventricular-pulmonary vascular interactions in different types of PAH, to determine the temporal changes in these interactions with PAH progression and to quantify the effects of exercise on right ventricular function. The inclusion of the subpopulation of PAH patients with systemic sclerosis (SSc) was a result of the anticipation that this group has worse arterial stiffening than other groups, and consequently more inefficient right ventricular-pulmonary vascular interactions, which account for their worse prognosis.

Inclusion Criteria:

1. Diagnosis of pulmonary arterial hypertension or a subtype
2. Referred for right heart catheterization
3. Age between 18 and 80 years
4. New York Heart Association (NYHA) functional class I, II, or III

Exclusion Criteria:

1. Recent syncope (within 1 year)

2. Severe skeletal or muscle abnormalities prohibiting exercise

3. Mixed etiology pulmonary arterial hypertension

4. Severe lung disease

   1. Test results indicating severe obstruction
   2. Total lung capacity < 60%

5. Pregnancy or breastfeeding

6. NYHA class IV patient

7. Contraindications to magnetic resonance imaging

8. Kidney dysfunction as determined by an estimated glomerular filtration rate (eGFR) of < 30 mL/min/1.73m2

9. Contraindication to gadolinium