A case report of paroxysmal complete atrioventricular block in a patient with dextrocardia and repaired tetralogy of Fallot

Background Some adults suffer sudden cardiac death after previous surgical repair of tetralogy of Fallot (TOF), and in such cases, ventricular tachycardia is believed to be the most frequent cause of death. However, we report a case of cardiac arrest due to paroxysmal complete atrioventricular block in an adult with dextrocardia and repaired TOF. Case summary A 49-year-old woman with dextrocardia and a history of surgical treatment for TOF lost consciousness three times. A previously implanted loop recorder showed a 60-second cardiac arrest, and complete atrioventricular block was diagnosed. An electrophysiological study showed prolongation of the His-ventricular interval but no ventricular tachycardia. A dual chamber pacemaker was implanted, and there has been no recurrence of syncope in the 23 months since implantation. Discussion There is little evidence for paroxysmal complete atrioventricular block in patients with repaired TOF. This case suggests that paroxysmal complete atrioventricular block can occur late after surgical repair of TOF, and research needs to elucidate whether it is the cause of sudden cardiac death in some patients with TOF.