Real World Difference After Changing Medication From Nonselective to Selective Endothelin Receptor Antagonist in Stable Eisenmenger Syndrome

1. Inclusion Criteria * Age at least 18 years * Patient who was scheduled to change Ambrisentan from Bosentan (prospective arm) or who already changed to Ambrisentan from Bosentan (retrospective arm) * Presence of cyanosis with \< 95 % arterial oxygen saturation (measured by transcutaneous pulse oximetry) or documented during exercise test (6 minute walk distance test or CPT stress test) * Bosentan treatment more than 3months before changing to Ambrisentan and stable medication dosage for 1 month before changing medication * Presence of PAH as diagnosed by invasive methods with Rp:Rs \> 0.75 measured at rest or diagnosed by echocardiography with TR Vmax \> 3.5m/s and bidirectional or right to left shunt. * One of the following diagnosis: i) non-corrected large congenital shunting defect at atrial, ventricular or arterial level: Partial anomalous venous return, atrial septal defect, ventricular septal defect, atrioventricular cushion defect, persistent ductus arteriosus, or a combination of these. ii) Surgically corrected shunting defect (diagnoses as above) with significant residual defect iii) Other diagnoses with univentricular physiology/haemodynamics. 2. Exclusion Criteria * pregnancy or lactation * women of child-bearing age who are sexually active without practicing reliable methods of contraception * any disease or impairment that, in the opinion of the investigator, excludes a subject from participation * substance abuse (alco…