Patients with idiopathic pulmonary arterial hypertension (IPAH) and iron deficiency were previously shown to have a decreased six-minute walking distance. Therefore the investigators hypothesized that intravenous iron administration would improve exercise capacity in iron deficient IPAH patients.

30 patients will be recruited for iron infusions. At baseline and after 12 weeks (endpoint)exercise test will be performed.

Background: Patients with pulmonary arterial hypertension (PAH) develop progressive right heart failure which eventually will lead to death. During progression of the disease the physical performance of the patients deteriorates. Maintaining their exercise capacity is a major goal in PAH treatment. Iron treatment is known to have a positive effect on physical performance in patients with left heart failure and iron deficiency. Whether this is also effective in patients with right heart failure (PAH) and iron deficiency is until now unknown.

Objective: To evaluate the effects of intravenous iron supplementation on exercise capacity in iron deficient IPAH patients.

Study design: Intervention study

Study population: Patients with idiopathic pulmonary arterial hypertension (IPAH) and iron deficiency

Patients receive an iron bolus infusion of 1000 mg iron after baseline measurements.

Main study parameters/endpoints:

Primary endpoint: six minute walking distance (6WMD) Secondary endpoints: cardiopulmonary exercise test, myoglobin concentration in quadriceps muscle, quadriceps muscle fiber strength, serum iron parameters, serum inflammatory parameters, quality of life (QOL), and NYHA functional class.

The patients will be hospitalised two days at the beginning and two days at the end of the study to perform the exercise and strength tests, six minute walking distance and for biopsy of the quadriceps muscle. Also NYHA functional class will be determined and a QOL questionnaire has to be filled in. After the baseline measurements an iron infusion will be given (Ferinject 1000mg).

The investigators hypothesize that iron deficient IPAH patients will benefit from iron treatment with improved exercise capacity reflected in an increased 6MWD.

Inclusion Criteria:

• Stable idiopathic pulmonary arterial hypertension (stable disease for at least 3 months)
• iron deficiency (serum iron below 10 μmol/l, decreased transferrin saturation (< 15% in females and < 20% in males) and serum ferritin < 100 μg/l) irrespective of the coexistence of anaemia

Exclusion Criteria:

• Current iron therapy (oral or iv)
• Current other study medication for PAH
• History of anaemia or current treatment for anaemia
• Liver function impairment
• Chronic disease other than PAH (rheumatism, asthma, chronic infection)
• Acute infection