Revisiting Cryoablation for AVNRT: A Commentary on Safety, Recurrence, and Clinical Implications

The article by Tachibana et al. [1] presents a comparative analysis of cryoablation versus radiofrequency ablation (RFA) in the context of the incidence of atrioventricular block (AVB) during slow pathway modification for atrioventricular nodal reentrant tachycardia (AVNRT). The attempt to compare the safety dynamics of the two ablation techniques is appreciable, particularly in the context of preserving AV nodal function, which is one of the major concerns in the treatment of AVNRT.

However, some methodological and interpretive aspects need to be explained further. Firstly, while the study reports a significantly higher incidence of transient AVB in the cryoablation group (24.1% vs. 6.4%, p < 0.01), the authors state that cryoablation is safer due to its reversibility and the gradual development of AV conduction issues. However, the high rate of AVB events in the cryoablation group is a concern regarding procedural stability and real-time safety during the ablation procedures undertaken in proximity to the compact atrioventricular node, particularly in those with smaller Koch's triangles [2].

Second, although the later onset of atrioventricular block (AVB) following cryoablation (mean to AVB 6.6 ± 3.7 s) compared with radiofrequency ablation (RFA) (1.2 ± 0.3 s) is an intriguing observation, it is not clearly indicated how such a finding relates in particular to effective risk reduction or improved operator response. Although the potential for earlier detection to be beneficial with delayed evolution is attractive, unless supported by active procedural monitoring strategies, this benefit remains theoretical [3].

Third, AVNRT recurrence was more prevalent in the cryo group (9.5% vs. 3.4%, p < 0.01) and challenges the precept of cryoablation's long-term effectiveness. The recurrence could be due to both lesion longevity and operator familiarity with ablation near the His bundle. The greater number of lesions ablated above the CS ostium in the cryo group lends support to this issue but is not addressed in detail. In addition, the research lacks adequate commentary on patient anatomy, lesion depth, or cooling dynamics, all of which are critical in the interpretation of energy delivery strategy results. Previous research has associated suboptimal cryo lesion formation with higher recurrence rates, especially in cases with delayed cooling or shallow lesion depth, issues that were not explored in this study.

Lastly, even though cryoablation showed no instances of permanent AVB in this cohort, the brief follow-up (median 221 days) and small sample size rule out conclusions about long-term AV nodal safety. Since certain AV nodal injuries may be delayed in presentation, longer follow-up and larger prospective trials would be required to confirm these results.

In conclusion, although the study indicates potential procedural safety of cryoablation in preventing permanent AVB, its increased transient AVB rates and AVNRT recurrence indicate that modality selection will still have to be individualized. Balanced interpretation, including procedural accuracy, risk of recurrence, and anatomy, is necessary in choosing ablation strategies for AVNRT.

The authors have nothing to report.

The authors have nothing to report.

The authors declare no conflicts of interest.

This article is linked to https://doi.org/10.1002/joa3.70072.