A New Mechanistic Insight Into Macro‐Reentrant Atrial Tachycardia in a Patient With Modified Fontan Circulation

Fontan flutter: an unusual example of an atrial tachycardia circuit in a patient with atrio-pulmonary connection (APC) conduit. The tachycardia circuit propagates around the base of the conduit (encircled by the arrows, showing direction of propagation from earliest [red] to latest [purple]). Radiofrequency ablation was delivered (red dots) and tachycardia terminated on ablation at the green arrow. A 46-year-old man with complex congenital heart disease was brought for ablation of symptomatic atrial tachycardia due to recurrent triggering of decompensated heart failure. Anatomy posed a significant challenge in terms of access and mapping; d-transposition of the great arteries, criss-cross heart, and unrestrictive inlet VSD, corrected in infancy with a modified Fontan conduit for right atrial venous return to the main pulmonary artery (APC). Additionally, femoral veins were inaccessible due to previous DVT. Electro-anatomical mapping and ablation were performed, with the aid of intracardiac echo, through a short epicardial deflectable sheath via the right internal jugular vein, with a decapolar reference catheter in the esophagus. This case demonstrates classical mechanisms of re-entrant atrial tachycardia around an anatomical barrier, propagated by a zone of slow-conducting scar. In order to create a line of block, it was necessary to deliver ablation lesions to the cavo-atrial junction, in the vicinity of the sinus node; initial junctional rhythm recovered to sinus rhythm shortly after. Innovative access, support and reference electrogram enabled ablation of this novel substrate, termed the “cavo-conduit isthmus” due to its mirror imaging of the classical cavo-tricuspid isthmus (Figures 1-5). The authors declare no conflicts of interest. The data that support the findings of this study are available from the corresponding author upon reasonable request.