title: Clinical usefulness of cryomapping for ablation of tachycardias involving perinodal tissue.
abstract: OBJECTIVE
  Radiofrequency (RF) ablation near the AV node carries a significant risk of AV block. We report our initial experience of using cryomapping function to aid the safe cryoablation close to the compact atrioventricular (AV) node.
  
  
  METHODS
  Five consecutive patients with para-Hisian accessory pathways (AP) ( n = 2), or focal atrial tachycardia (AT) originating near the AV node ( n = 3) underwent cryoablation using a 7F 4 mm-tipped catheter. At each prospective ablation site, cryo-mapping (-30 degrees C) which causes transient electrical dysfunction was performed, and in the absence of AH interval prolongation, a full cryoablation (<or=-70 degrees C) was applied to the same site.
  
  
  RESULTS
  The AT foci, left in 2 patients and right in 1, and the APs were located 1.9 +/- 3.0 mm and 4.5 +/- 8.1 mm from the catheter recording the His deflection in two orthogonal radiographic projections. A His signal (0.18 +/- 0.07 mV) was recorded at the site of successful cryoablation in both patients with AP and 1 with right AT. There was no change in AV nodal function during/after ablation. At each successful cryoablation site, interruption of target pathway/focus function was observed during cryo-mapping after 19.8 +/- 12.4 s. Full cryoablation at sites where cryo-mapping had not caused an effect did not then produce any further electrophysiologic effect. All pathways and foci were ablated successfully without complications, using 3.2 +/- 3.9 cryothermic applications alone in 4 patients, and after a supplementary RF ablation in 1. All patients remained free of arrhythmia at 15 +/- 8 months follow-up.
  
  
  CONCLUSIONS
  Cryomapping may help identify sites for safe and effective ablation of pathways and foci located near the AV node.
authors.affiliation: St. Mary's Hospital, London, UK. tom.wong@imperial.ac.uk
authors.forename: Tom
authors.initials: T
authors.lastname: Wong
authors.forename: Vias
authors.initials: V
authors.lastname: Markides
authors.forename: Nicholas S
authors.initials: NS
authors.lastname: Peters
authors.forename: D Wyn
authors.initials: DW
authors.lastname: Davies
mesh_terms: D000328:Adult; D001281:Atrial Fibrillation / Q000175:diagnosis* / Q000601:surgery*; D001283:Atrioventricular Node / Q000601:surgery; D018780:Body Surface Potential Mapping; D017115:Catheter Ablation / Q000009:adverse effects / Q000379:methods*; D003131:Combined Modality Therapy; D003452:Cryosurgery / Q000379:methods*; D004562:Electrocardiography; D005260:Female; D005500:Follow-Up Studies; D006327:Heart Block / Q000517:prevention & control; D006801:Humans; D008297:Male; D008875:Middle Aged; D018570:Risk Assessment; D012494:Sampling Studies; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index; D016896:Treatment Outcome