ABSTRACT
Cyanotic lesions account for only about 25% of congenital heart disease (CHD), but many are life-threatening in the first few weeks of life. Even with surgery, 15-20% of infants will die in the first year of life. Cyanosis is clinically detectable when reduced haemoglobin exceeds 5 g/100 ml and is more easily recognized in the newborn with a high haemoglobin than in an anaemic child. Cyanosis may occur because the lungs are underperfused owing to a right-to-left shunt bypassing the lungs (e.g. Fallot’s tetralogy) or because there is mixing of the systemic and pulmonary circulations (e.g. transposition of the great arteries with ventricular septal defect, VSD. In the latter case, lung perfusion is normal or excessive. Cyanosis may be apparent in the neonatal period or become increasingly obvious over the first few months of life, particularly when the baby feeds or cries. In the older child, cyanosis is usually obvious at rest, exercise tolerance is reduced and clubbing occurs.
