Published online before print December 3, 2008, doi: 10.1161/CIRCEP.108.807925
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Original Articles |
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
From the Heart Rhythm Institute (K.Y, H.N., A.I., R.L., W.M.J.), Department of Medicine/Section of Digestive Diseases (K.A.S.), Department of Pathology (J.V.P), Veterans Administration Medical Center, University of Oklahoma Health Sciences Center, Oklahoma City, Okla; and ProRhythm, Inc. (E.J., J.M., Y.Z.), Ronkonkoma, NY.
Correspondence to Hiroshi Nakagawa, MD, PhD, Heart Rhythm Institute, University of Oklahoma Health Sciences Center, 1200 Everett Drive (TUH-6E 103), Oklahoma City, OK 73104. E-mail hiroshi-nakagawa{at}ouhsc.edu
Received July 30, 2008; accepted November 3, 2008.
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.
Methods and 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 
50°C occurred only for HIFU Eso-balloon distance 
2 mm. For HIFU/SFU inside the PV, Eso-temp was 50°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 50°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 50°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.
Key Words: catheter ablation • atrial • fibrillation • complications
CLINICAL PERSPECTIVE
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