Anatomy of the Cavotricuspid Isthmus for Radiofrequency Ablation in Typical Atrial Flutter

Background: Radiofrequency (RF) catheter ablation is one of the most common strategies for the current management of cavotricuspid isthmus (CTI)-dependent atrial flutter (AFL). The interindividual anatomic variability can influence the duration and outcome of ablation procedure.

Objective: The purpose of this study was to establish complication rates in patients undergoing RF catheter ablation for CTI-dependent AFL, assess the role of CTI morphology in procedural success, and determine the anatomic variability of CTI ex vivo.

Methods: RF catheter ablation for CTI-dependent AFL was performed in 337 consecutive patients. Angiographically determined CTI morphology was classified as either simple or complex due to pouchlike recesses. Macroscopic and histologic examination of the CTI was performed in 104 heart specimens from consecutive autopsies.

Results: Complex CTI anatomy was present in 10.9% of AFL patients. RF application time to achieve bidirectional isthmus block was longer in patients showing pouchlike recesses than in those without (10.7 vs 8.3 min; P= .025). Acute procedure failure or major complications occurred in 3 cases, all with complex CTI anatomy. A pouchlike recess of the CTI was present in 9.6% of autopsy hearts. Histomorphometric analysis of the CTI atrial wall demonstrated that the central level was the thinnest in the 3 sectors and the paraseptal level was the thickest.

Conclusion: Although RF catheter ablation is a safe and effective procedure for AFL treatment, CTI anatomic complexity can affect ablation parameters and outcome. Standard definition of CTI morphologic variants is recommended. Preprocedural assessment of CTI anatomy might lead to personalized ablation preventing potential difficulties and complications.