Abstract
BACKGROUND: Atrial tachycardia is a frequent late complication after Fontan surgery, with complex mechanisms involving scars and baffle suture lines. CASE SUMMARY: A 42-year-old man with prior lateral tunnel Fontan presented with recurrent supraventricular tachycardia at 180 beats/min. Coronary sinus catheterization was not feasible. Intracardiac echocardiography (ICE) showed the right atrium divided by the baffle into caval and pulmonary venous chambers. Activation mapping revealed extensive low-voltage substrate, with ∼70% of the tachycardia cycle length localized to the pulmonary venous right atrium. Entrainment responses were consistent at several sites but poor at others, indicating a macro-re-entrant circuit revolving around the baffle-crista terminalis suture line. Linear ablation across this isthmus terminated flutter; tachycardia was noninducible thereafter. DISCUSSION: This case illustrates a rare mechanism of Fontan-related flutter, defined by ICE and entrainment, emphasizing the need to consider baffle-related circuits in complex anatomies. TAKE-HOME MESSAGE: Baffle-related macro-re-entry should be suspected in patients who underwent lateral tunnel Fontan; ICE plus entrainment can guide effective ablation.