Cryo-ablation for septal tachycardia substrates in pediatric patients: mid-term results.

OBJECTIVES The aim of this study was to evaluate the efficacy and safety of catheter-based cryo-therapy for septal tachycardia substrates in pediatric patients. BACKGROUND Cryo-therapy may be particularly useful for ablation of septal tachycardias, including atrioventricular nodal re-entry tachycardia (AVNRT), atrioventricular reciprocating tachycardia (AVRT), and ventricular tachycardia (VT) originating high in the conduction system. METHODS Thirty-one pediatric patients (median = 13.7 years, range 5.3 to 19.6 years) with septal tachycardia substrates underwent cryo-ablation (CA). Twenty-two had AVNRT, 8 AVRT, and 1 VT. Applications were considered cryo-maps (CMs) if the temperature set-point was -35 degrees C or the application time was <120 s. Other lesions were considered CAs. RESULTS A total of 242 CMs (4 per patient, range 0 to 40 CMs) and 89 CAs (2 per patient, range 1 to 8 CMs) were performed, for a total cryo-therapy time of 689 s/patient (range 158 to 3,300 s). Procedural success with cryo-therapy was achieved in 27 of 31 patients (87.1%), including two procedures with a His potential at the CA location and three performed in tachycardia. The success rate for AVNRT was higher than for AVRT (95.5% vs. 62.5%, p < 0.05). For AVRT, a sustained effect on accessory pathway conduction occurred -3.3 +/- 4.9 s after reaching -25 degrees C, whereas for those sites at which the effect was transient, the effect took 24.8 +/- 25.5 s (p = 0.07). Transient atrioventricular (AV) block occurred during eight cryo-applications (1 CA, 7 CMs) with immediate return of normal AV conduction upon cessation of application. There were no other complications. CONCLUSIONS Cryo-therapy was used to effectively and safely ablate septal tachycardias in this group of 31 pediatric patients. Cryo-therapy may be more effective for AVNRT than septal AVRT.