Long-Term Outcomes of 6-mm Versus 8-mm Cryoablation for Pediatric AVNRT: A Large Single-Center Study

Cryoablation is commonly used for pediatric atrioventricular nodal reentrant tachycardia (AVNRT) due to its excellent safety profile and nearly zero risk of permanent atrioventricular (AV) block. However, limited data comparing 6- and 8-mm cryocatheter tips in large pediatric cohorts are available. This study aims to evaluate and compare the procedural characteristics, acute success, and long-term outcomes of 6- and 8-mm cryoablation catheters in children undergoing slow pathway modification for AVNRT.

We retrospectively reviewed 343 pediatric patients (≤18 years) who underwent cryoablation for AVNRT between 2016 and 2025. Patients were treated with either a 6-mm (n = 182) or an 8-mm (n = 161) cryocatheter. Baseline characteristics, electrophysiological parameters, procedural metrics, complications, and recurrence outcomes were analyzed. All procedures used three-dimensional electroanatomical mapping to improve anatomical accuracy and reduce fluoroscopy exposure.

Patients in the 8-mm group were older and heavier and had a higher rate of prior ablation (21.1% vs. 6.0%), indicating greater procedural complexity. Procedure duration, total cryotherapy time, and the number of lesions were significantly longer in the 8-mm group. Acute success rates were excellent in both groups (99.5% vs. 100%), and there were no cases of permanent AV block, pericardial effusion, or major complications. Over a median follow-up of 69 months in the 6-mm group and 30 months in the 8-mm group, recurrence rates were 15.4% and 10.6%, respectively (p = 0.246), showing a favorable but non-significant trend toward fewer recurrences with the 8-mm catheter.

Both 6- and 8-mm cryoablation catheters offer highly safe and effective treatment for pediatric AVNRT. Despite being used in more complex cases, the 8-mm catheter achieved comparable acute results and showed a potential long-term benefit, supporting its use in selected patient groups.