Coarctation and interrupted aortic arch — branching viva

Stage 1 — The neonatal collapse

The examiner shows you a three-day-old baby in shock with a pH of 7.10 and a lactate of 8 mmol per litre. The brachial pulses are strong, the femoral pulses are weak. A ductal-dependent arch obstruction is the working diagnosis. [4]

• What is your working diagnosis, and what bedside sign drives it? [3]
• What drug do you start immediately, at what dose, and what is its mechanism? Start prostaglandin E1 at 0.01 to 0.05 micrograms per kilogram per minute; it relaxes ductal smooth muscle to reopen the duct. [4]
• What is the most dangerous side effect, and how do you manage it in a baby being transferred to a cardiac centre? Anticipate apnoea; the baby must travel intubated or with skilled airway support. [4]

Stage 2 — The prenatal diagnosis of interrupted aortic arch

The examiner tells you the baby in the next cot had a prenatal diagnosis of interrupted aortic arch type B and is being worked up for surgery. [8]

• How is interrupted aortic arch classified, and what is the most common type? Type A distal to the left subclavian, type B between the left carotid and the left subclavian (most common), type C distal to the left carotid (rarest). [6]
• What genetic test is essential, and what does the associated syndrome mean for the perioperative plan? Chromosomal microarray for 22q11.2 deletion; the syndrome brings hypocalcaemia, immunodeficiency and airway anomalies that change the operative plan. [8]
• Outline the principles of the surgical repair: restore arch continuity by direct anastomosis and close the VSD, ideally as a single-stage repair. [5]

Stage 3 — The adolescent with coarctation and Turner syndrome

The examiner moves to the outpatient clinic. A fourteen-year-old girl with short stature and a webbed neck has an arm blood pressure of 150/90 and a leg blood pressure of 110/70, with radio-femoral delay. [9]

• What does the four-limb blood-pressure gradient tell you? The arm-to-leg gradient with radio-femoral delay is the bedside signature of coarctation of the aorta. [1]
• What genetic investigation is now essential, and what non-cardiac follow-up will she need? A karyotype for Turner syndrome, which drives growth-hormone and gonadal management alongside the cardiac surveillance. [9]
• Why does she need lifelong cardiac surveillance even after a successful repair? Residual hypertension from intrinsic aortic vasculopathy, re-coarctation risk, and the bicuspid aortic valve all declare over decades. [11]