Atrial tachycardia after conversion to extra-cardiac Fontan conduit: critical role of surgery-related electrical gaps

We present a 32-year-old man with a history of complex congenital heart disease who developed symptomatic atrial tachycardia after conversion of atriopulmonary anastomosis to extra-cardiac Fontan circulation with right atrial resection. A percutaneous ablation using a trans-Gore-Tex puncture was performed (Panel A). The presence of a large atrial septal defect allowed complete bi-atrial mapping. The tachycardia was mapped using a high-density mapping catheter (Orion, Boston Scientific). The activation map identified a macro-reentrant clockwise peri-tricuspid flutter. The tachycardia used two electrical gaps (Panel B). The first gap was anteriorly located between the line of atriotomy and the tricuspid annulus (TA). The second gap was posteriorly located between the line of atriotomy and the cavo-tricuspid isthmus and was protected by a tricuspid patch. Discrete ablation targeting the anterior gap successfully terminated the tachycardia. The anterior line was blocked after connection to the TA. This case demonstrates the creation of a substrate sustaining atrial re-entrant arrhythmias after right atrial resection in patients undergoing conversion to extra-cardiac Fontan conduit. Local ablation during the surgical repair aiming to block the electrical gaps would prevent surgery-related re-entrant atrial arrhythmias and avoid complex percutaneous interventions. The full-length version of this report can be viewed at: https://www.escardio.org/Education/E-Learning/Clinical-cases/Electrophysiology.