title: Transcatheter cryoablation of tachyarrhythmias in children: initial experience from an international registry.
abstract: OBJECTIVE
  We sought to describe the early pediatric experience of transcatheter cryoablation, and identify whether specific arrhythmia substrates and/or ablation locations were particularly suited to cryoablation.
  
  
  BACKGROUND
  Radiofrequency (RF) ablation has become established therapy for pediatric tachyarrhythmias. However, challenges remain in terms of the safety and efficacy of RF ablation in specific locations; new methods may address these issues.
  
  
  METHODS
  Prospective data were available for 64 patients age 13 +/- 4 (mean +/- SD) years undergoing cryoablation at 14 centers participating in the Cryocath International Patient Registry. Dysrhythmia duration was 5.0 +/- 4.2 years, with diagnoses of atrioventricular node re-entrant tachycardia (AVNRT) (n=30), anteroseptal (n=11), midseptal (n=5), or other (n=15) accessory pathway (AP) mediated AV re-entry, ventricular tachycardia (VT) (n = 3), and ectopic atrial tachycardia (EAT) (n=2). Two patients had more than one arrhythmia substrate. Transcatheter cryoablation was offered by cardiologist preference after written informed procedural consent of each patient and/or legal guardian. Cryomapping was performed at -30 degrees C and cryoablation was delivered with 4-min applications at -75 degrees C.
  
  
  RESULTS
  Acute success was achieved in 45 of 65 (69%) cryoablation patients, with best success rates in AVNRT (83%) and right septal AP (75%), and lower success rates in other AP (43%), VT (66%), and EAT (0%). No device-related adverse events were reported. The success of radiofrequency (RF) ablation applied in 14 cryoablation failures was 4 of 4 for AVNRT patients, 1 of 1 for anteroseptal AP patients, 5 of 6 for other AP patients, 0 of 1 for VT patients, and 0 of 2 for EAT patients.
  
  
  CONCLUSIONS
  Transcatheter cryoablation is a safe and well-tolerated alternative to RF ablation in pediatric patients on the basis of our initial experience. Success is highest in AVNRT and in substrates recognized as technically challenging or risky for RF ablation.
authors.affiliation: Division of Cardiology, Department of Pediatrics, Hospital for Sick Children, University of Toronto, Ontario, Canada. joel.kirsh@sickkids.ca
authors.forename: Joel A
authors.initials: JA
authors.lastname: Kirsh
authors.forename: Gil J
authors.initials: GJ
authors.lastname: Gross
authors.forename: Stephen
authors.initials: S
authors.lastname: O'Connor
authors.forename: Robert M
authors.initials: RM
authors.lastname: Hamilton
mesh_terms: D000293:Adolescent; D017115:Catheter Ablation / Q000379:methods; D002648:Child; D002675:Child, Preschool; D003452:Cryosurgery; D006801:Humans; D007223:Infant; D012042:Registries; D013610:Tachycardia / Q000601:surgery*; D013611:Tachycardia, Atrioventricular Nodal Reentry / Q000601:surgery