The incidence of congenital heart disease is also known to be higher in siblings or offspring of those already affected. The incidence rises from 6-9/1000 to 30-40/1000 for siblings of affected children. Unfortunately the genetic basis for this remains largely unknown however it is the subject of intense ongoing research. Acyanotic congenital heart disease is by far the commonest group, comprising ventricular septal defect, atrial septal defect, atrioventricular septal defect, arterial duct, coarctation of the aorta, pulmonary stenosis and aortic stenosis. Together this group account for about 90% of congenital heart disease. The principal cyanotic lesions are tetralogy of Fallot, transposition of the great arteries, pulmonary atresia, tricuspid atresia and Ebsteins anomaly, altogether comprising about 5% of congenital heart disease. Other rare conditions such as total anomalous pulmonary venous drainage, hypoplastic left heart syndrome and other forms of univentricular heart constitute the remaining 5%. No AVSD will resolve spontaneously and all need surgical repair as well as antibiotic prophylaxis. Where a child presents with heart failure due to a large ventricular component the medical management is as described for VSD. Classically it was described as the tetrad of VSD, right ventricular outflow tract obstruction, aorta overriding the crest of the ventricular septum and right ventricular hypertrophy. Early palliation in excessively cyanotic infants is by modified Blalock Taussig shunt as described under tetralogy of Fallot. Further palliation follows the Fontan-type pattern and will be summarised later in the univentricular heart section. HLHS is the broad term given to describe inadequacy of the left ventricular size in combination with stenosis or atresia of the mitral and aortic valves and hypoplasia of the aortic arch. Coarctation is a common association.