Canine model of esophageal injury and atrial-esophageal fistula after applications of forward-firing high-intensity focused ultrasound and side-firing unfocused ultrasound in the left atrium and inside the pulmonary vein.
BACKGROUND
Left atrial-esophageal fistula is a serious and poorly understood complication of catheter ablation of atrial fibrillation. The purpose of this study was to (1) develop a canine model of esophageal injury and left atrial-esophageal fistula after applications of forward-firing high-intensity focused ultrasound (HIFU) and side-firing unfocused ultrasound (SFU); (2) examine the relationship to esophageal temperature (Eso-temp); and (3) study the evolution of injury/healing.


RESULTS
Twenty dogs were studied. After transeptal puncture, HIFU catheter (ProRhythm Inc; 13 dogs) was positioned close to the esophagus, either outside (n=6) or inside (n=7) the inferior pulmonary vein (PV). In 7 other dogs, an SFU catheter was placed deep inside the PV, close to the esophagus. A balloon (20- to 25-mm diameter) with 7 thermocouples (2-mm separation) was positioned in the esophagus (Eso-balloon). Variable air filling of the Eso-balloon controlled the distance from the esophagus to the sonication source, pressing the esophagus against left atrium/PV. One to 9 (median, 5) HIFU (35 W) and 5 to 7 (median, 5) SFU (40 W) sonications were delivered for 40 seconds. Maximum luminal Eso-temp was closely related to HIFU Eso-balloon distance. For HIFU outside PV, Eso-temp >or=50 degrees C occurred only for HIFU Eso-balloon distance <or=2 mm. For HIFU/SFU inside the PV, Eso-temp was >or=50 degrees C, with HIFU Eso-balloon distance up to 6.8 mm. Endoscopy identified esophageal ulcer immediately after ablation in 11 of 13 HIFU dogs and 7 of 7 SFU dogs, all with Eso-temp >or=50 degrees C. Endoscopy at 2 weeks showed ulcer healing in 5 of 11 chronic dogs and ulcer size progression with relaxation of the lower esophageal sphincter and esophagitis in 6 dogs. Two dogs developed left atrial-esophageal fistula and died at 2 weeks.


CONCLUSIONS
This model produces esophageal ulcer when Eso-temp is >or=50 degrees C. Eso-temp is higher with HIFU/SFU applications closer to the esophagus and with HIFU/SFU applications inside the PV. Ulcer progression and left atrial-esophageal fistula were associated with reflux esophagitis.
Yokoyama
Katsuaki
K
Heart Rhythm Institute, Department of Medicine/Section of Digestive Diseases, Department of Pathology, Veterans Administration Medical Center, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA.
Nakagawa
Hiroshi
H
Seres
Kenneth A
KA
Jung
Eugene
E
Merino
Jaime
J
Zou
Yong
Y
Ikeda
Atsushi
A
Pitha
Jan V
JV
Lazzara
Ralph
R
Jackman
Warren M
WM
D000818:Animals; D001831:Body Temperature; D017115:Catheter Ablation / Q000009:adverse effects*; D004195:Disease Models, Animal; D004285:Dogs; D004937:Esophageal Fistula / Q000209:etiology* / Q000473:pathology; D004942:Esophagitis, Peptic / Q000209:etiology / Q000473:pathology; D004945:Esophagoscopy; D004947:Esophagus / Q000293:injuries* / Q000473:pathology; D005402:Fistula / Q000209:etiology* / Q000473:pathology; D006325:Heart Atria / Q000601:surgery; D006331:Heart Diseases / Q000209:etiology* / Q000473:pathology; D011667:Pulmonary Veins / Q000601:surgery*; D013997:Time Factors; D014456:Ulcer / Q000209:etiology / Q000473:pathology; D014464:Ultrasonic Therapy / Q000009:adverse effects*; D014945:Wound Healing