Transposition of the great arteries — formative SAQs

SAQ 1 (10)

A six-hour-old term infant is noted on the postnatal ward to be centrally cyanosed. He is pink above the clavicles but dusky in the feet, and on closer inspection the lower limbs are pinker than the hands. He is feeding and alert, with a respiratory rate of 48 and no recession. A saturation of 72 per cent does not improve with one hundred per cent oxygen. The chest X-ray shows a narrow mediastinum with an egg-shaped cardiac silhouette and increased pulmonary vascular markings. [2] [1]

a) What is the most likely diagnosis, and state two features of the clinical picture that point specifically to it rather than to a primary respiratory cause. (2 marks) [2]

b) Outline your immediate management, naming the drug, its dose and the airway preparation it demands. (3 marks) [10]

c) An hour later the saturation has fallen to 58 per cent and the lactate has risen to 6.2 millimoles per litre. State the next procedure and why. (2 marks) [1]

d) The echocardiogram confirms simple transposition with an intact septum. Name the definitive operation, state the principle that governs its timing, and explain why the timing matters for the left ventricle. (3 marks) [4]

SAQ 2 (10)

A twenty-eight-year-old man attends the emergency department with new palpitations and dizziness. He had a Mustard atrial-switch repair for transposition of the great arteries in infancy. His electrocardiogram shows a regular narrow-complex tachycardia at one hundred and fifty per minute with sawtooth waves in the inferior leads. [4]

a) What is the rhythm, and why is this arrhythmia particularly dangerous in this patient? (3 marks) [4]

b) Outline the late complications that a patient with an atrial-switch repair is at risk of, naming at least four. (3 marks) [1]

c) Explain why the atrial switch was superseded by the arterial switch, in terms of which ventricle is left as the systemic pump. (2 marks) [4]

d) State the principles of long-term surveillance for the adult who had an arterial switch (Jatene) repair instead, naming at least three structures that must be followed. (2 marks) [1]