Electrical isolation of the cavotricuspid isthmus aneurysm: a novel strategy for refractory atrial tachyarrhythmias with complex anatomical variants: a case report.

BACKGROUND: Cavotricuspid isthmus (CTI) is a part of the re-entrant circuit of atrial flutter (AFL), and its linear ablation is the method of choice for treating CTI-dependent AFL. We describe our experience of a case of multiple atrial tachycardias (ATs) originating from the CTI aneurysm and the challenges encountered during its electrophysiological management.

CASE SUMMARY: The patient, a 61-year-old woman with hereditary non-polyposis colorectal cancer, presented with recurrent supraventricular tachycardia resistant to conventional treatment with anti-arrhythmic medication and electrical cardioversion. The 12-lead electrocardiogram finding suggested CTI-dependent AFL. In the initial ablation session, right atrium angiography revealed the presence of a CTI aneurysm. We completed the CTI bidirectional block, but AT recured immediately. Multiple focal ATs originated around tricuspid valve annulus, and CTI-dependent re-entrant AT was induced in the second session. Since multiple fractionated potential was observed in the CTI aneurysm during the AT mapping, we decided to create electrical isolation of the CTI aneurysm by lateral and septal CTI block lines. After CTI aneurysm isolation, ATs were eliminated. After 3 months, ATs recured. The reconnected lateral CTI block line was re-completed in the third session, and CTI re-isolation was achieved. Since the third session, there were no recurrent ATs.

DISCUSSION: In this case, the CTI aneurysm was crucial and underlies the mechanism of multiple ATs. Electrical isolation of the CTI aneurysm was effective. This case emphasizes the importance of detailed anatomical assessment, particularly in patients with unusual CTI structures, and illustrates the successful use of novel mapping technologies.