title: Cryoablation in pediatric atrioventricular nodal reentry: electrophysiologic effects on atrioventricular nodal conduction.
abstract: BACKGROUND
  Cryoablation for treatment of atrioventricular nodal reentrant tachycardia (AVNRT) is safe and efficacious. Information on the effects of cryoablation on atrioventricular (AV) nodal conduction is limited.
  
  
  OBJECTIVE
  The purpose of this study was to evaluate the effects of cryoablation on AV nodal conduction in pediatric patients with AVNRT.
  
  
  METHODS
  We retrospectively analyzed electrophysiologic studies before and after successful cryoablation. Patients were divided into two groups: group 1 (n = 22, age 14 +/- 3 years) had baseline discontinuous atrial-to-His interval (AH) conduction curves; and group 2 (n = 13, age 12 +/- 4 years, P = .054) had continuous curves.
  
  
  RESULTS
  At baseline, group 1 had longer measurements of maximal AH with A1A2, AV nodal effective refractory period, and AV block cycle length. Postcryoablation, both group 1 and group 2 showed decreases in maximal AH with A1A2 pacing or atrial overdrive pacing and in the finding of PR > or = RR with atrial overdrive pacing (group 1: 55% vs 5%, P < .001; group 2: 69% vs 0%, P < .001). A significant increase in overall AV effective refractory period and a decrease in AV block cycle length were found in group 1 but not group 2. Fifty percent of group 1 patients had complete abolition of slow pathway conduction.
  
  
  CONCLUSIONS
  Successful cryoablation for treatment of AVNRT is associated with a reduction in PR > or = RR and with decreases in maximal AH with A1A2 pacing or atrial overdrive pacing. Further study is needed to determine the usefulness of these parameters for assessment of ablation efficacy or as proxies for AVNRT inducibility.
authors.affiliation: Division of Cardiology, Department of Pediatrics, University of California, San Francisco, California 94143-0632, USA. kathryn.collins@ucsf.edu
authors.forename: Kathryn K
authors.initials: KK
authors.lastname: Collins
authors.forename: Anne M
authors.initials: AM
authors.lastname: Dubin
authors.forename: Nancy A
authors.initials: NA
authors.lastname: Chiesa
authors.forename: George M
authors.initials: GM
authors.lastname: McDaniel
authors.forename: George F
authors.initials: GF
authors.lastname: Van Hare
mesh_terms: D000293:Adolescent; D016275:Atrial Function; D002036:Bundle of His / Q000503:physiopathology / Q000601:surgery; D002648:Child; D003452:Cryosurgery; D022062:Electrophysiologic Techniques, Cardiac; D005260:Female; D005500:Follow-Up Studies; D006327:Heart Block / Q000503:physiopathology / Q000601:surgery; D006801:Humans; D008297:Male; D012189:Retrospective Studies; D013611:Tachycardia, Atrioventricular Nodal Reentry / Q000503:physiopathology* / Q000601:surgery*; D016896:Treatment Outcome