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The Challenges of Preventing Lethal Esophageal Damage During Atrial Fibrillation Ablation Continue

An atrioesophageal fistula is a rare but lethal complication that results from both intraoperative and transcatheter radiofrequency (RF) energy applications to the posterior left atrium (LA), and the mortality rate is reported to be around 75%.1,2 Although its occurrence rate ranges from 0.05% to 1.3% depending on the reports, it appears to be underestimated, and at least 60 patients have suffered from this complication.2,3 Furthermore, other manifestations of esophageal thermal damage caused by RF energy deliveries have been reported not to be uncommon. The most frequent form of thermal damage has been found to be esophageal erythema and/or erosion of the anterior esophageal wall in 35.7–57.1% of patients as determined by esophageal endoscopy performed within 24 hours after RF ablation either with nonirrigated 8-mm tip or open-irrigated 3.5-mm tip ablation catheters.4 The fistula results from thermal damage to the anterior esophageal walls,1,3 and a sustaining inflammation in addition to the precipitating effects of the gastric acid cause the formation of the fistula.1-3 The thermal effects provoked by the RF energy delivery consist of three major factors, including resistive heating directly induced by the RF energy, convective cooling to the surrounding coolant, and conductive heating of the surrounding tissue.5,6 The extent of resistive heating is limited to within a few millimeters,5,6 and the distance between the LA posterior wall and anterior wall of the esophagus has been reported to be around 6 mm;7-9 therefore, the conductive heating is the only factor that appears to cause the fistula formation. Some prophylactic practices used to minimize the risk of an esophageal fistula have been raised, which include limiting the RF energy power and/or duration, identification of the esophageal location, real-time monitoring of the luminal esophageal temperature and/or pain during the RF ablation, and the use of intracardiac echocardiography,2-4,10-13 but no definitive methods have been proposed. Berjano et al. first proposed in 2005 an idea of esophageal cooling in order to prevent the thermal damage to the esophagus,14 and elegantly showed it by a computer simulation model. Tsuchiya et al. reported that esophageal cooling using a cooled waterirrigated intraesophageal balloon effectively lowered the luminal esophageal temperature in patients with atrial fibrilla-