Entrance‐Site Ablation in Atrial Tachycardia Involving Epicardial Conduction: A Case Series

Q: What is the clinical evidence from this study?

Study design: Observational. Population: Atrial tachycardia involving epicardial conduction unresponsive to initial exit-site ablation (n=9). Intervention: Entrance-site radiofrequency ablation guided by entrainment mapping. Primary outcome: Acute procedural success (termination of atrial tachycardia and non-inducibility).

Q: What does this research mean for the field?

Entrance-site radiofrequency ablation successfully terminates atrial tachycardias involving epicardial conduction and achieves noninducibility when conventional exit-site ablation is insufficient. Novelty: ClaimNovelty.METHODOLOGICAL. Consensus alignment: ConsensusAlignment.NEUTRAL.

Yuichiro Sakamoto; Yuko Uemura; Ryo Yamaguchi; Hirokazu Naganawa; Daisuke Yoshimoto; Takahiko Suzuki

doi:10.1002/joa3.70390

June 1, 2026Journal of ArrhythmiaOpen Access

Entrance‐Site Ablation in Atrial Tachycardia Involving Epicardial Conduction: A Case Series

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Key result

Entrainment-guided entrance-site ablation terminates refractory epicardial atrial tachycardia in ~100% of cases.

n=9

Figures

Graphical abstract published by Journal of Arrhythmia — Graphical abstract · Published by Journal of Arrhythmia · CC BY

Why the study?

Treatment of AT involving epicardial conduction is challenging, and endocardial exit-site RF ablation is sometimes ineffective, resulting in treatment failure.

Does entrainment-guided entrance-site radiofrequency ablation safely terminate tachycardia and prevent recurrence in patients with atrial tachycardia involving epicardial conduction who are unresponsive to conventional exit-site ablation?

Key Points

To investigate the feasibility and efficacy of targeting endocardial entrance sites for radiofrequency ablation in atrial tachycardias involving epicardial conduction after failed exit-site ablation.
Retrospective case series of 10 atrial tachycardias involving epicardial conduction in 9 patients (mean age 71 ± 11 years; 56% female) unresponsive to initial exit-site ablation.
Entrance sites were identified by high-resolution endocardial mapping and entrainment, localized as the furthest downstream site where the postpacing interval closely matched the atrial tachycardia cycle length.
Median atrial tachycardia cycle length was 328 ms (289–356), with a missing activation time of 140 ms (93–157) accounting for 42% (35–47) of the cycle length.
Epicardial conduction pathways involved the vein or ligament of Marshall (n=4), the septopulmonary bundle (n=4), and combinations involving Bachmann's bundle (n=2).

Study Design

Type

Observational (n=9)

Multicenter

No

Structured PICO

Does entrainment-guided entrance-site radiofrequency ablation safely terminate tachycardia and prevent recurrence in patients with atrial tachycardia involving epicardial conduction who are unresponsive to conventional exit-site ablation?

P

Population

9 adults (mean age 71, 56% female) with atrial tachycardia involving epicardial conduction that failed initial exit-site ablation, followed for a median of 198 days.

I

Intervention

Entrance-site radiofrequency (RF) ablation guided by detailed entrainment mapping, targeting the most downstream site where the postpacing interval closely approximated the AT cycle length.

O

Outcome

Acute procedural success, defined as termination of atrial tachycardia and non-inducibility.surrogate

Systematic identification and RF ablation of the entrance site for epicardial conduction using entrainment mapping provides an effective strategy for treating complex atrial tachycardias when conventional exit-site ablation fails.

Limitations

Retrospective study design with potential selection bias.
Detailed entrainment mapping was not systematically performed in all atrial tachycardia cases during the study period.
Orthodromic capture of the exit site from the defined entrance site was not systematically assessed in all cases.
Bidirectional functional interruption of the presumed epicardial pathway could not be confirmed.
Diagnosis of VOM/LOM-related AT was based solely on mapping; no VOM catheterization or ethanol infusion was performed to confirm.
Patients were retrospectively selected based on the performance of entrance-site ablation, meaning the true incidence and proportion requiring this approach cannot be determined.
Evaluation of conduction in the opposite direction was not systematically performed; bidirectional functional interruption could not be confirmed.
VOM/LOM-related ATs were diagnosed based solely on endocardial activation mapping and entrainment findings, without insertion of a thin electrode catheter into the VOM.
Ethanol infusion into the VOM was not used as a first-line treatment for VOM/LOM-related cases.

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Implication

Hypothesis-generating for entrance-site ablation in refractory epicardial atrial tachycardia; prospective trials needed before clinical adoption.

Abstract

Background Treatment of atrial tachycardia (AT) involving epicardial conduction remains challenging. While endocardial exit sites can serve as targets for radiofrequency (RF) ablation, this approach is sometimes ineffective and may result in treatment failure. Methods This retrospective study systematically investigated entrance‐site ablation for 10 ATs involving epicardial conduction in nine patients who were unresponsive to initial exit‐site ablation. The entrance site—identified using high‐resolution endocardial mapping and entrainment as the most downstream site where the postpacing interval closely approximated the AT cycle length (ATCL)—was targeted for RF ablation. Results The median ATCL was 328 ms (289–356). The missing activation time was 140 ms (93–157), corresponding to 42% (35–47) of the ATCL. Possible epicardial conduction inferred from entrainment findings was attributed to the vein/ligament of Marshall in four ATs, the septopulmonary bundle in four, and combinations involving the Bachmann bundle in two. RF ablation at the entrance site terminated four ATs with a single RF application, while in the remaining six, additional lesions with progressive cycle‐length prolongation achieved termination. Noninducibility was confirmed in all patients. Conclusions Systematic identification and ablation of the entrance site of epicardial conduction using detailed entrainment mapping provide a practical and effective strategy for managing ATs involving epicardial conduction, particularly when conventional exit‐site ablation is insufficient.

Discussion

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Cite This Study

Sakamoto et al. (2026) conducted an observational in Atrial tachycardia involving epicardial conduction unresponsive to initial exit-site ablation (n=9). Entrance-site radiofrequency ablation guided by entrainment mapping was evaluated on Acute procedural success (termination of atrial tachycardia and non-inducibility). Systematic entrainment-guided identification and radiofrequency ablation of the entrance site of epicardial conduction successfully terminated atrial tachycardia in 100% of cases unresponsive to exit-site ablation.

synapsesocial.com/papers/6a32623f8b0a6d04ea8e6a0a https://doi.org/10.1002/joa3.70390

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Entrance‐Site Ablation in Atrial Tachycardia Involving Epicardial Conduction: A Case Series

Figures

Key Points

Study Design

Structured PICO

Limitations

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Implication

Abstract

Discussion

Cite This Study

Entrance‐Site Ablation in Atrial Tachycardia Involving Epicardial Conduction: A Case Series

Figures

Key Points

Study Design

Structured PICO

Limitations

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Implication

Abstract

Discussion

Cite This Study

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