Bradyarrhythmias, heart block and pacing — branching viva

Examiner opening (Examiner)

You are the paediatric registrar on the neonatal unit. A two-day-old infant has a routine postnatal heart rate of fifty-five beats per minute. She is mildly mottled and feeding slowly, and the midwife has noted that the mother is "a runner" and attributed the slow rate to inherited fitness. The mother has systemic lupus erythematosus and is known to be anti-Ro positive. A twelve-lead ECG shows atrial and ventricular complexes that are independent of each other, with a narrow-QRS escape rhythm at fifty-five per minute. Talk me through your assessment and management. ^[2]

Exemplar opening (Candidate)

This infant has congenital complete (third-degree) atrioventricular block, almost certainly immune-mediated given the maternal systemic lupus erythematosus and anti-Ro positivity, and the midwife's attribution to inherited fitness is the classic error — a slow rate in a newborn is never normal and is complete heart block until an ECG proves otherwise. The ECG shows atrioventricular dissociation with a narrow-QRS junctional escape rhythm, which is the expected escape from below the blocked AV node. Her mottling and slow feeding mean she is becoming symptomatic from the low rate. My immediate plan is to admit her with continuous cardiac monitoring and intravenous access, obtain an echocardiogram to exclude associated structural congenital heart disease and endocardial fibroelastosis, send maternal and infant anti-Ro and anti-La titres, and assess whether she needs acute rate support or pacing while a permanent pacemaker is planned. ^{[2] [4]}