title: Successful use of "cryo-mapping" to avoid phrenic nerve damage during ostial superior vena caval ablation despite nerve proximity.
abstract: BACKGROUND
  The SVC may require ablation to treat atrial fibrillation. Phrenic nerve proximity identified with pacing maneuvers may preclude ablation.
  
  
  METHODS
  We tested a new method using "cryo-mapping" to ablate despite nerve proximity.
  
  
  RESULTS
  Of 833 patients undergoing ablation, 110 (12%) had arrhythmogenic substrate at the SVC/RA junction. Of these 110 patients, 66 (60%) had consistent diaphragmatic stimulation when pacing at 10 mA at the prospective site of ablation. Of these 66 patients, 7 had continued arrhythmogenicity despite attempts to modify this substrate. For these 7 patients, we paced 4 cm into the SVC where consistent phrenic nerve stimulation was obtained, and cryoablation at -30 degrees C was performed at sites requiring ablation. In 6 of 7 patients (86%), with continued diaphragmatic capture, cryoablation at -70/-80 degrees C was then performed. In 1 of 7 patients (14%), diaphragmatic stimulation ceased at -30 degrees C, and energy delivery stopped. In the 6 patients in whom cryoablation was completed, the arrhythmogenic substrate was successfully ablated without phrenic nerve injury.
  
  
  CONCLUSIONS
  A novel "cryo-mapping" technique during phrenic nerve pacing can be used to successfully ablate arrhythmogenic substrate at the SVC/RA junction despite phrenic nerve proximity.
authors.affiliation: Department of Medicine, Mayo Clinic, Rochester, MN, USA.
authors.forename: Chadi
authors.initials: C
authors.lastname: Dib
authors.forename: Suraj
authors.initials: S
authors.lastname: Kapa
authors.forename: Brian D
authors.initials: BD
authors.lastname: Powell
authors.forename: Douglas L
authors.initials: DL
authors.lastname: Packer
authors.forename: Samuel J
authors.initials: SJ
authors.lastname: Asirvatham
mesh_terms: D001281:Atrial Fibrillation / Q000503:physiopathology / Q000601:surgery*; D002304:Cardiac Pacing, Artificial; D017115:Catheter Ablation / Q000009:adverse effects; D003452:Cryosurgery; D003964:Diaphragm / Q000294:innervation; D004562:Electrocardiography; D005260:Female; D006325:Heart Atria / Q000503:physiopathology; D006801:Humans; D008297:Male; D008875:Middle Aged; D010791:Phrenic Nerve / Q000033:anatomy & histology* / Q000293:injuries / Q000601:surgery; D014683:Vena Cava, Superior / Q000503:physiopathology / Q000601:surgery*