Cardiac or respiratory cause of hypoxia in a newborn

A term baby boy was delivered overnight by emergency caesarean section for pathological cardiotocography. An uncle died in childhood due to ‘a problem with the aorta’.\n\nAfter initial cry, he required resuscitation including chest compressions. He was stabilised on nasal continuous positive airway pressure therapy (nCPAP). Oxygen saturations remained labile with a notable preductal and postductal gradient of 10% with brief preductal saturations of greater than 90%. Cardiovascular examination was normal. A chest X-ray was taken at 2 hours of life (figure 1).\n\n\n\nFigure 1 \nAnteroposterior chest radiograph taken at two hours of life.\n\n\n\n‘Egg on a string sign’ suggests which congenital cardiac condition?\n\n1. Coarctation of the aorta\n\n2. Ebstein anomaly\n\n3. Tetralogy of Fallot\n\n4. Total anomalous pulmonary venous return\n\n5. Transposition of the great arteries\n\nWhat pathological finding is seen on this X-ray?\n\nWhat emergency treatment should be considered?\n\nWhich investigation …