A cyanotic newborn is suspected of having congenital heart disease. He has an increased left ventricular impulse and a holosystolic murmur along the left sternal border. The ECG shows left-axis deviation and left ventricular hypertrophy (LVH). Which of the following is the most likely diagnosis?

Patients with tricuspid atresia typically have a hypoplastic right ventricle, and therefore the ECG shows left-axis deviation and LVH; this translates to a left ventricular impulse on physical examination. Almost all other forms of cyanotic congenital heart disease are associated with elevated pressures in the right ventricle and increased right ventricular impulse. In those conditions, therefore, the ECG will show right-axis deviation and right ventricular hypertrophy.