title: Cryoablation of substrates adjacent to the atrioventricular node: acute and long-term safety of 1303 ablation procedures.
abstract: OBJECTIVE
  Radiofrequency (RF) ablation is effective for ablation of atrial arrhythmias. However, RF ablation in the vicinity of the atrioventricular (AV) node is associated with a risk of inadvertent, irreversible high-grade AV block, depending on the type of substrate. Cryoablation is an alternative method. The objective was to investigate the acute and long-term risks of AV block during cryoablation.
  
  
  RESULTS
  We studied 1303 consecutive cryoablations of substrates in the vicinity of the AV node in 1201 patients (median age 51 years, range 6-89 years) on acute and long-term impairment to the AV nodal conduction system. The arrhythmias treated were AV nodal reentrant tachycardias (n=1116), paraseptal and superoparaseptal accessory pathways (n=100), and focal atrial tachycardias (n=87). In 158 (12%) procedures, cryomapping (38 cases) or cryoablation (120 cases) were stopped due to transient AV block (first-degree AV block 74 cases, second-degree AV block 67 cases, and third-degree AV block 17 cases) after which another site was tested. Transient AV block occurred within seconds of mapping up to 3 min of ablation. The incidence of AV block was similar for different substrates. In most cases, AV nodal conduction was restored within seconds but in two cases transient AV block lasted 21 and 45 min, respectively. There were no cases of acute permanent AV blocks. No late AV blocks occurred during follow-up (mean 24 months, range 6-96 months).
  
  
  CONCLUSIONS
  Cryoablation adjacent to the AV node carries a negligible risk of permanent AV block. Transient AV block during ablation is a benign finding.
authors.affiliation: Department of Cardiology, Karolinska University Hospital, S-141 86 Stockholm, Sweden.
authors.forename: Per
authors.initials: P
authors.lastname: Insulander
authors.forename: Hamid
authors.initials: H
authors.lastname: Bastani
authors.forename: Frieder
authors.initials: F
authors.lastname: Braunschweig
authors.forename: Nikola
authors.initials: N
authors.lastname: Drca
authors.forename: Kristjan
authors.initials: K
authors.lastname: Gudmundsson
authors.forename: Göran
authors.initials: G
authors.lastname: Kennebäck
authors.forename: Bita
authors.initials: B
authors.lastname: Sadigh
authors.forename: Jonas
authors.initials: J
authors.lastname: Schwieler
authors.forename: Jari
authors.initials: J
authors.lastname: Tapanainen
authors.forename: Mats
authors.initials: M
authors.lastname: Jensen-Urstad
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001145:Arrhythmias, Cardiac / Q000175:diagnosis / Q000503:physiopathology / Q000601:surgery*; D054537:Atrioventricular Block / Q000175:diagnosis / Q000209:etiology* / Q000503:physiopathology; D001283:Atrioventricular Node / Q000503:physiopathology*; D002648:Child; D003452:Cryosurgery / Q000009:adverse effects*; D022062:Electrophysiologic Techniques, Cardiac; D005260:Female; D006325:Heart Atria / Q000503:physiopathology / Q000601:surgery; D006801:Humans; D008297:Male; D008875:Middle Aged; D018570:Risk Assessment; D012307:Risk Factors; D013997:Time Factors; D016896:Treatment Outcome; D055815:Young Adult
keywords: AV block; AVNRT; Accessory pathway; Atrial tachycardia; Cryoablation