Electrophysiological characteristics of epicardial breakthrough during catheter ablation of perimitral atrial flutter

Chheng Chhay, Chu Yu Hsu, Shih Lin Chang*, Yenn Jiang Lin, Li Wei Lo, Yu Feng Hu, Fa Po Chung, Ting Yung Chang, Chin Yu Lin, Yuan Hung, Chih Min Liu, Ling Kuo, Shin Huei Liu, Lia Ahli, Ming Jen Kuo, Wen Han Cheng, Pei Heng Kao, Wei Tso Chen, Thien Chuong Nguyen Khac, Wei Shiang LinShih Ann Chen

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


Introduction: Unsuccessful endocardial ablation for perimitral atrial flutter (AFL) could be attributed by the epicardial bridging. Objective: This study aimed to investigate the electrophysiological characteristics of epicardial breakthrough during catheter ablation of perimitral AFL. Materials and methods: This retrospective study recruited 40 patients who received successful catheter ablation of perimitral AFL from January 2016 to June 2021. The patients were divided into two groups: group 1 (n = 18) successful endocardial ablation, and group 2 (n = 22) successful epicardial ablation following unsuccessful endocardial ablation owing to incomplete mitral block or unachievable termination AFL. The local electrogram (EGM) interval of coronary sinus (CS) duration perimitral AFL was measured before catheter ablation. Results: There was no significant difference in the baseline characteristics between the two groups. In group 2, 60% of successful epicardial ablation was performed in intra-CS ablation and 40% in VOM ethanol infusion. Group 2 patients had a longer EGM interval of distal CS than that in group 1 (CS1-2: 64.2 17.5 vs. 42.4 0.09 ms, P = 0.008, CS3-4: 57.13 19.4 vs. 43.8 7.5 ms; P = 0.001). The conduction velocity at successful site was slower in group 2 compared to group 1 (0.18 0.05 vs. 0.75 0.19 m/s, P = 0.040). In the multivariate analysis, distal EGM interval (CS1-2) was identified as independent predictor of the need of epicardial ablation with the optimal cutoff of 49 ms. Conclusion: Longer EGM interval in distal CS during perimitral AFL was observed in perimitral AFL patients with epicardial breakthrough following endocardial-failed ablation, which may be associated with the need of epicardial ablation.

Original languageEnglish
Article number1030916
JournalFrontiers in Cardiovascular Medicine
StatePublished - 17 Nov 2022


  • EGM interval of distal CS
  • atrial fibrillation
  • catheter ablation
  • epicardial breakthrough
  • perimitral atrial flutter


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