He was born vaginally at term to a 19-year-old mother with scant prenatal care. She reports no problems during the pregnancy other than third trimester hypertension. On physical examination vital signs and growth parameters are normal. Head is normocephalic. Fontanelles are flat. Chest has good air movement without distress. Heart has increased apical impulse that is displaced to the left. Left ventricular impulse is prominent. The first heart sound is increased in intensity; the second heart sound is single. A 4 out of 6 holosystolic murmur along the left sternal border is found. Distal pulses are normal. Capillary refill is less than 3 seconds. Abdomen is soft, nontender, and the liver is felt 3 cm below the costal margin. 

Which of the following is the most likely diagnosis?

A. Transposition of the great arteries

B. Truncus arteriosus

C. Tricuspid atresia

D. Tetralogy of Fallot

E. Hypoplastic left heart syndrome

The correct answer is C. 

The patient in the question clearly has a congenital heart disease. 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 and likely notably diminished deflections of right ventricular forces. Additionally, right atrial overload may manifest as tall P waves in lead II (although this finding is not seen on the ECG with this case). 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, the ECG will show right-axis deviation and right ventricular hypertrophy.

(Hay et al, pp 565-566. Kliegman et al, pp 1580-1582. McMillan et al, pp 1543-1546. Rudolph et al, pp 1824-1825.) 

Sources:

Question & Explanation: Yetman RJ, Hormann MD. Pediatrics: PreTest Self-Assessment and Review, 14e. New York, NY: McGraw-Hill Education; 2016.

Photo: Wells RG. Diagnostic Imaging of Infants and Children; 2015.