PAH: pulmonary arterial hypertension; PVR: pulmonary vascular resistance. ^aWith surgery or intravascular percutaneous procedure. ^bThe size applies to adult patients. However, also in adults the simple diameter may be not sufficient for defining the haemodynamic relevance of the defect and also the pressure gradient, the shunt size and direction, and the pulmonary to systemic flows ratio should be considered (Web Table II).