Congenital Heart Disease — Cyanotic

A 3-day-old neonate born at term presents with severe cyanosis (SpO₂ 65% on room air) and respiratory distress. Clinical examination reveals a single loud S2 and an ejection systolic murmur at the left upper sternal border. Chest X-ray shows an 'egg-on-string' appearance with pulmonary oligemia. Which investigation is most appropriate to confirm the diagnosis and guide immediate management?

A 6-month-old female infant from rural Maharashtra presents with progressive cyanosis (SpO₂ 65% on room air), failure to thrive, and squatting posture during episodes of dyspnea. Clinical examination reveals a single loud S₂ and a systolic ejection murmur at the left upper sternal border. Chest X-ray shows a 'boot-shaped' heart with right ventricular hypertrophy and decreased pulmonary vascular markings. Echocardiography confirms tetralogy of Fallot (TOF) with severe right ventricular outflow tract (RVOT) obstruction. The infant is currently on no medications. What is the most appropriate immediate management?

A 6-month-old infant with known tetralogy of Fallot (TOF) presents with a 'Tet spell'—sudden-onset severe cyanosis, dyspnea, and loss of consciousness. After initial resuscitation with oxygen, knee-chest positioning, and morphine, the episode resolves. The parents ask about the anatomic basis of the cyanosis and whether the child needs surgery. Which investigation is most appropriate to assess the severity of the right ventricular outflow tract obstruction and guide timing of surgical repair?

A 3-day-old neonate born to non-consanguineous parents presents with cyanosis and poor feeding. Chest X-ray shows a 'boot-shaped' heart with decreased pulmonary vascular markings. Echocardiography confirms a right-to-left shunt at the ventricular level. Which is the most common cyanotic congenital heart defect in this presentation?

A 3-day-old male neonate born to non-consanguineous parents presents with cyanosis noticed since birth. On examination, he is tachypneic (RR 65/min), has clubbing of fingers, and a single loud S2. Chest X-ray shows an 'egg-on-string' appearance with decreased pulmonary vascularity. Echocardiography reveals anterior aorta overriding a ventricular septal defect with right ventricular outflow tract obstruction. What is the most likely diagnosis?