Pilot Study of the Safety and Efficacy of Carvedilol in Pulmonary Arterial Hypertension

Inclusion Criteria: * idiopathic, familial or associated PAH, WHO group 1 * NYHA class II or III * clinically stable with optimized PAH treatment for at least 3 months * no or minimal evidence of fluid overload or volume depletion, with or without diuretic treatment * age \> 18 years * mean pulmonary artery pressure (mPAP) \> 25 mmHg * 6 minute walk distance (6MWD) over 100m Exclusion Criteria: * Structural heart disease unrelated to PAH * Recent (\<3 months) treatment with an intravenous positive inotropic agent * current use of β-blockers * history of reactive airways disease * history of adverse reaction to β-blockers * heart block on ECG or resting heart rate \< 60 bpm * cardiac index \< 1.8 l/min/m2 * systemic hypotension (systolic pressure \< 90 mmHg) * pulmonary capillary wedge pressure \> 15 mmHg * inability to give informed consent * contraindications to CT and/or PET scanning * coagulopathy (INR\>1.5 or platelet count\<50000/mm3) * severe renal insufficiency (creatinine clearance \<30 ml/min/m2) * malignancy or any co-morbidity limiting survival or conditions predicting inability to complete the study.