Pulmonary arterial hypertension (PAH) in patients with congenital heart disease (CHD) usually develops secondary to chronic volume overload of the pulmonary circulation following left to right shunt. This overload leads to elevated pulmonary artery pressure (PAP) and later to increased pulmonary vascular resistance. This causes pressure overload in the right heart, and thereby right ventricular and right atrial dysfunction, which may implicate considerable morbidity and even mortality.