Efficacy and safety of cryoenergy in the ablation of atrioventricular reentrant tachycardia substrates in children and adolescents.

INTRODUCTION: Cryoenergy has evolved as a safe and effective alternative for ablation of arrhythmia substrates in adult patients. Due to two specific features, cryomapping and cryoadhesion, this technique appears very attractive for pediatric patients minimizing complications and fluoroscopy time. The aim of the study was to investigate efficacy and safety of cryoenergy in the ablation of supraventricular tachycardia (SVT) substrates in pediatric patients.

PATIENTS AND METHODS: Thirty-two patients (mean age: 10.1 +/- 3.5 years) with SVT (accessory pathways: n = 19; atrioventricular nodal reentrant tachycardia (AVNRT): n = 13) underwent electrophysiological study under the guidance of the LocaLisa system. Cryomapping at -30 degrees C was performed to predict cryoablation outcome and to ascertain AV conduction. Cryoenergy was delivered subsequently at the same spot (cryoablation at -70 degrees C) as verified by the LocaLisa system.

RESULTS: Successful cryoablation was achieved in 24 of 32 patients (75%). A median of two (1-10) cryoablations were delivered. In the remaining 8 patients, radiofrequency (RF) current application was effective in 5 resulting in an overall success rate of 90.6%. In 4 patients with an accessory pathway cryomapping was not predictive for successful cryoablation (negative predictive value 66.6%). In 3 additional patients with AVNRT transient high-grade AV block occurred during cryoablation despite previous "safe" cryomapping at the same location. No other major complications were noted.

CONCLUSION: Cryoablation of SVT substrates in pediatric patients was associated with a lower success rate compared to RF catheter ablation. Cryomapping decreased the number of permanent lesions but did not predict cryoablation outcome in all tachycardia substrates.