<prompt> A five-day-old, full term male infant was severely cyanotic at bih. His chest X ray showed Egg-on -side appearance. Prostaglandin E1 was administered initially and later balloon atrial septosomy was done which showed improvement in oxygenation. The most likely diagnosis of this infant is:Tetralogy FallotTransposition of great vesselsTruncus aeriosusTricuspid atresia  <response>: - Given features suggests towards diagnosis of TGA Transposition of the great vessels with an intact ventricular septum presents with early cyanosis, normal-sized hea, normal or slightly increased pulmonary vascular markings, and an ECG showing right-axis detion and right ventricular hyperophy - Balloon atrial septostomy: Helpful in a baby with TGA with intact ventricular septum for initial stabilization, It creates a communication between the left and right atria - helps in mixing blood of systemic and pulmonary circulations maintain relatively better oxygenation. -TREATMENT OF TGA: PGE1 analogue - Keep ductus aeriosus open Balloon atrial septostomy Rashkind procedure - Emergency procedure Aerial switch operation Jatenes repair - Definitive surgery 