Intermittent P-Wave Loss during Sustained Intra-atrial Reentrant Tachycardia in a Fontan's Patient: Elucidating the Mechanism by High-Density Mapping

Objectives: Atrial arrhythmias can be complex in Fontan's patients. Here, we describe the elucidation of the mechanism and catheter ablation of an intra-atrial reentrant tachycardia (IART) with frequent intermittent P-wave loss during sustained local reentry.

Methods: A 26-year-old male patient with double inlet left ventricle and L-transposition of great arteries after modified Fontan's anastomosis with an autologous lateral tunnel presented with symptomatic atrial tachycardia. At the age of 4 years, the stenotic tunnel was augmented by spindle-shaped Gore-Tex patch. At the age of 15 years, linear cavotricuspid isthmus ablation had been performed for drug-resistant atrial flatter. Because of third degree atrioventricular block, a dual chamber pacemaker with an endovascular atrial lead and an epimyocardial ventricular lead had been implanted. For the electrophysiologic study, a bipolar screw was placed as reference in the right lateral tunnel wall via the right subclavian vein. High-density activation and substrate mapping of the lateral tunnel was performed with a grid-patterned electrode configuration. Off-line analysis of IART cycles with versus IART cycles without P-waves was performed. It revealed counterclockwise local reentry in the anterior tunnel wall with the protected isthmus at the inferior border of the Gore-Tex patch. During the cycles with P-waves, excitation spread through a zone of slow conduction and an adherent region toward the “left-sided” atria, while this zone and adherent region of the tunnel was not excited during cycles without P-waves. We conclude that this zone and the adherent is responsible for spreading the excitation toward the atria whose excitation is necessary for P-waves in the surface ECG. The atrial tachycardia was terminated by a single ablation lesion with irrigated contact-force controlled RF energy. During 6 months of follow-up, there was no recurrence of the tachycardia.

Conclusion: High-density mapping enabled the elucidation of the mechanism of a sustained IART with intermittent P-wave loss. To the best of our knowledge, neither this atrial tachycardia nor the mechanism has been described yet.

Publication History

Article published online:
21 February 2021