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]

SAQ 2 — The staged Fontan pathway (10 marks, 15 minutes)

A three-year-old child with hypoplastic left heart syndrome is being assessed for the Fontan completion after a Norwood and a bidirectional Glenn. [10]

a) Name the three stages of single-ventricle palliation in order and state what each stage achieves for the circulation. (4 marks) [10]

b) Explain why the interstage period between stage one and stage two carries the highest mortality, and describe the components of a home-monitoring programme. (3 marks) [12]

c) List the four pillars of long-term Fontan morbidity and state the disposition of the child after Fontan completion. (3 marks) [10]