Transposition of great vessels (TGA) is defined as aoa arising from the right ventricle and pulmonary aery from the left ventricle. In patients with TGA, the oxygenated pulmonary venous blood recirculates in the lungs whereas the systemic venous blood recirculates in the systemic circulation. The pulmonary aery saturation is thus always higher than the aoic saturation. Survival depends on the mixing available between the two circulations. Patients of complete TGA with intact ventricular septum are cyanotic at bih. Since the interatrial communication results in poor mixing, the neonates present with rapid breathing and congestive failure secondary to hypoxemia within the first week of life. Physical examination shows severe cyanosis, congestive failure, normal first sound, single second sound and an insignificant grade one to two ejection systolic murmur. The electrocardiogram shows right axis detion and right ventricular hyperophy. The thoracic roentgenogram shows cardiomegaly with a narrow base and plethoric lung fields. The cardiac silhouette can have an "egg on side" appearance: The right upper lung fields appear more plethoric than other areas. The thymic shadow is often absent. Patients of TGA with VSD have increased pulmonary blood flow; mixing at the ventricular level determines the severity of cyanosis. They develop congestive failure around 4-10 weeks of age. Physical findings consist of cyanosis, cardiomegaly, congestive failure, normal first sound, single or normally split second sound and grade II-IV ejection systolic murmur. Apical third sound gallop or a mid-diastolic rumble may be present. Electrocardiogram shows right axis detion with biventricular, right ventricular or left ventricular hyperophy. Chest X-ray shows cardiomegaly, plethoric lung fields and features of pulmonary venous hypeension. The aerial switch operation is now established as the treatment of choice for TGA, Prostaglandin El can help reduce cyanosis in selected cases by keeping the PDA open. Interim palliation can be accomplished through a balloon atrial septostomy. Reference: Essential Paediatrics; O.P. Ghai; Page no: 425