Background  Epidemiology Affects around 1/250 UK babies. The vast majority survive until adulthood, and 10% are not even diagnosed until then. Many conditions have a variable presentation, with some apparent at birth or early infancy (poor feeding, lethargy, SOB, heart failure) and others only becoming symptomatic (if at all) later in life. This page describes the commoner conditions, including the three commonest: VSD, ASD, and bicuspid aortic valve. Structures affected Valves: bicuspid aortic valve, aortic stenosis, pulmonary stenosis, tricuspid atresia. Septa: atrial or ventricular. Vessels: coarctation of the aorta, transposition of the great arteries, patent ductus arteriosus, persistent truncus arteriosus. Ventricles: hypoplastic left heart. Atrial septal defect (ASD) Pathophysiology Ostium secundum ('second hole') defects high in septum are the commonest clinically-significant ASD. Usually first present in adulthood, though more significant defects can be detected as ear...