Atrial septal defect is the commonest congenital heart disease in the adult, barring of course bicuspid aortic valve. Description at: https://johnsonfrancis.org/professional/asd-overview-and-secundum-asd/ ASD being a post tricuspid shunt, development of pulmonary hypertension and Eisenmenger syndrome is delayed and survival to adult age group is common. Some even argue that pulmonary hypertension in ASD is primary pulmonary hypertension which the individual was otherwise destined to develop.