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 (nϭ6) or inside (nϭ7) 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 Ն50°C occurred only for HIFU Eso-balloon distance Յ2 mm. For HIFU/SFU inside the PV, Eso-temp was Ն50°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 Ն50°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 Ն50°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. (Circ Arrhythmia Electrophysiol. 2009;2:41-49.)

A number of complications have been associated with ablation of atrial fibrillation (AF), including arterial thrombo-embolism, pulmonary vein stenosis, phrenic nerve injury, and pericardial tamponade. [1][2][3][4] Esophageal injury, manifested as esophageal perforation or left atrial-esophageal fistula, has been reported after catheter or surgical ablation of AF using radiofrequency (RF) current 5-8 and catheter ablation using high-intensity focused ultrasound (HIFU). 9 Left atrial-esophageal fistula usually is associated with a very high morbidity and mortality, including air embolism and sepsis. Article see p 162Esophageal injury during RF ablation in the left atrium is thought to be thermal injury. 10 -12 In this issue of Circulation: Arrhythmia and Electrophysiology, Singh et al 13 sought to determine whether the risk of esophageal injury would be reduced by measuring the luminal esophageal temperature (LET) during ablation and maintaining the LET below 38.5°C. The LET was measured using a 9Fr flexible temperature probe (with a single thermocouple) in the esophagus. The temperature probe was maneuvered in cranial-caudal direction to position the thermocouple close to the ablation catheter tip in the left atrium.We agree in principal with the authors' conclusion that esophageal temperature-monitoring may reduce the risk of esophageal injury during AF ablation. An esophageal ulcer was observed by endoscopy 1 to 3 days postablation in 4 of 67 (6%) patients with LET-monitoring (and discontinuing RF application at LET Ն38.5°C) compared to 5 of 14 (36%) patients without LET-monitoring. Importantly, in patients with LET-monitoring, this study showed no significant difference between patients with and without an esophageal ulcer and the maximum LET during ablation or the number of RF applications producing an increase in LET to Ն38.5°C. This study did not identify a safety LET cut-off, below which an esophageal ulcer would not occur. There was also no relationship between the average RF power and the maximum LET.The lack of relationship between the LET and the occurrence of esophageal ulceration in this study may relate to the inability of currently available probes (a single thermocouple within the esophagus) to locate and measure the highest esophageal temperature during left atrial ablation. This problem was identified in a canine model of esophageal injury where RF, HIFU, and cryo-ablation were performed in the left atrium adjacent to the esophagus. 12,14,15 An air-filled balloon (20 to 25 mm diameter) was positioned in the esophagus to move the esophagus close to the posterior left atrium. Temperature was measured along the esophageal balloon by 7 thermocouples (2 mm separation) facing the left atrium and the ablation catheter. Esophageal ulceration occurred consistently when the maximum LET was Ն49.6°C for RF energy and HIFU energy. 12,14 Lower LET was not associated with ulceration. During cryo-ablation, esophageal ulceration occurred consistently when the minimum LET was Յ1.3°C. 15 Esophageal ulceration was...

Clinical prompts are superior to evidence-based lectures for improving physician colorectal cancer screening practices. These prompts are simple low-cost measures that can improve quality of care.

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