Truncus arteriosus and single-ventricle physiology — formative SAQs

SAQ 1 — The four-week-old with cyanosis and heart failure (10 marks, 15 minutes)

A four-week-old term infant who was mildly dusky from birth presents with increasing tachypnoea, sweating on feeds and poor weight gain. The pulses are bounding with a wide pulse pressure, the second heart sound is single, and the chest radiograph shows increased pulmonary markings. The echocardiogram confirms truncus arteriosus. ^[3]

a) State the four anatomical features of truncus arteriosus and explain how they produce the bedside findings. (4 marks) ^[2]

b) Explain the mechanism by which an unrepaired truncus progresses from cyanosis to heart failure over the first weeks of life. (3 marks) ^[3]

c) Outline the definitive surgical repair and the genetic test that must be requested. (3 marks) ^{[1] [5]}