Approaches to Minimize Risk of an AEF
A rare but potentially devastating complication of AF ablation is injury to the esophagus, with the possible outcome of AEF or esophageal perforation leading to mediastinal infection, stroke, and/or death.866,867,1398 Another complication that is thought to be related to thermal injury to the periesophageal vagal plexus is gastroparesis.868 More information concerning the incidence, presentation, and management of these complications is presented under Section 10. Because of the serious consequences of an AEF, it is important to attempt to prevent severe esophageal and periesophageal injury. Some operators design the ablation lesions to avoid the esophagus. The location of the esophagus can be visualized using a variety of approaches, including multidetector CT, topographic tagging of the esophageal position with an EAM system, barium paste, and ICE.869,870,871,872,873,874,875,876 It is important to know that esophagus location can change during the procedure, and repeated imaging or visualization is needed to account for the motion of the esophagus. However, it is difficult to accomplish complete PV ablation without some ablation in close proximity to the esophagus. Strategies to prevent and treat esophageal injury follow.

Reduced Power Delivery on the Posterior Wall
Higher power and greater depth of tissue heating or cooling are associated with increased risk of esophageal injury. In order to minimize injury to the esophagus during RF applications on the posterior wall close to the esophagus, several approaches can be employed, including (1) reduction of RF power (e.g., ≤25 W); (2) shortening RF application time (e.g., ≤20 seconds); and/or (3) decreasing CF (e.g., ≤10 grams). The writing group recommends that RF power be reduced when creating lesions along the posterior wall near the esophagus (Class I, LOE C-LD, Table 3). Some reports employed the use of light conscious sedation to use pain to identify potential esophageal injury. However, there are conflicting data on the specificity of the pain response. It has been proposed that an alternative energy source, such as the CB for PVI, could minimize esophageal injury877,878; however, AEF or periesophageal vagal plexus injury after CBA has been reported.879,880 There are also data that other heat-based energy sources, such as high-intensity focused ultrasound or laser energy, can damage the esophagus.501,502,700,701,705,881 Although each of these approaches is variously adopted by different ablation centers, each remains largely unproven due to the rarity of an AEF as a complication.

Esophageal Temperature Monitoring
A strategy to avoid esophageal injury employed by 65% of the writing group members is luminal esophageal temperature monitoring, used to identify potentially dangerous heating of the esophagus.882,883,884,885 Unfortunately, because the esophagus is broad, the lateral position of the temperature probe or mapping electrode might not align with the ablation electrode, and the operator could receive a false impression of safety.1398 There is general agreement among those operators who employ temperature probes that an increase in esophageal temperature should trigger interruption of RF energy delivery. Three-quarters of the writing group members terminate ablation if they observe a 1°C or 2°C rise in temperature from baseline, or a recorded temperature of 39°C–40°C. During CBA, two-thirds of the writing group members monitor esophageal temperature, and terminate cooling if the esophageal temperature reaches 20°C–25°C. A variety of esophageal temperature probes are available for clinical use.886 A recent study has shown the superior thermodynamic profile of multisensor esophageal recording systems; however, no clinical trial has demonstrated superiority in terms of reducing AEFs.646,647 This type of study would be impossible to perform due to the very low event rate of this complication. Among the writing group members who employ esophageal temperature monitoring, single thermocouple probes are used by two-thirds and multithermocouple probes are employed by one-third. The potential benefit of multithermo-couple probes must be weighed against their increased complexity and cost.886,887,888,889 The writing group recommends that it is reasonable to use an esophageal temperature probe during RF ablation procedures to monitor esophageal temperature to help guide energy delivery (Class IIa, LOE C-EO, Table 3).
Another strategy to protect the esophagus uses active cooling.890,891,892,893 This technique has not been tested on a large scale, and the data describing this technique are limited. Selected operators use mechanical displacement of the esophagus.894,895 This technique appears to be promising, but its use has been limited to a small number of patients and is therefore an unproven approach.

Pharmacological Prophylaxis
Esophageal ulcers are found in a 5%–40% of patients following AF ablation. It is hypothesized that AEF occurs because there is transmural necrosis of both the atrium and esophagus with subsequent ulcer erosion from gastroesophageal reflux.896,897 To prevent ulcer erosion, proton pump inhibitors (PPIs) have been employed, and are used by 65% of the writing group members after ablation. PPIs are highly effective in gastroesophageal reflux disease by reducing the acidity of the gastric juice and healing esophagitis.898,899,900 PPIs are effective in reducing the size of iatrogenic-induced ulcers, therefore could also be helpful for ablation-induced ulcers.901 Other mechanisms, such as traumatic injury of the esophageal wall, could also play a potential role in fistula formation, although there is no proof of this concept. Prophylactic short-term use of PPIs after AF ablation is assumed to be effective; however, further large randomized studies are required to determine whether PPIs reduce AEFs. Because of the low event rate of AEFs, such a study will not likely be performed. At the moment, PPI therapy is justified as a singular preventive treatment.

Role and Indications for Endoscopic Screening for Ulceration Following AF Ablation
Because AEF can cause septicemia and air embolism leading to death, early detection of esophageal tissue injuries is essential. Data evaluating the role of gastrointestinal endoscopy for detection of esophageal tissue lesions are limited. In 185 patients who underwent gastrointestinal endoscopy after LA RF ablative therapy, ulcer-like or hemorrhagic esophageal thermal lesions (diameter: 2–16 mm) were observed in 14.6% of the patients.902 These lesions only occurred when the intra-luminal esophageal temperature had reached more than 41°C. The odds of an esophageal lesion increased by a factor of 1.36 (95% CI 1.07–1.74; P = .012) for every 1°C rise in temperature.
Gastrointestinal endoscopy in a cohort of 425 patients 1 to 3 days after AF catheter ablation, in whom intraluminal esophageal temperatures higher than 41°C were recorded, revealed esophageal tissue lesions in 11.6% of asymptomatic patients.903 Hence, these observations suggest that asymptomatic patients could benefit from routine gastrointestinal endoscopy after RF catheter ablative therapy when the intraluminal esophageal temperature during the procedure has reached a certain target temperature, such as 41°C. However, there are no reports on the value of this type of follow-up endoscopic examination after ablative therapy. Only one study did a follow-up endoscopy at least 7 days after the first examination in patients with an esophageal lesion diameter >5 mm and found regression of all 3168 lesions.903 A PPI was used in all the patients for 4 weeks after ablation.

Role and Indications for CT Imaging for Diagnosis of Atrioesophageal Fistula
After ablation, symptoms and findings suggesting the possibility of evolving AEF include chest pain, painful swallowing, fever, leukocytosis, TIA, and/or stroke typically occurring between 1 and 3 weeks postablation. If esophageal injury is suspected, CT imaging with intravenous and water-soluble oral contrast is recommended.904,905,906 Findings on CT imaging on an AEF include mediastinal or pericardial free air, evidence of free communication between the esophagus and pericardium or atrium, and inflammatory phlegmon between the esophagus and the heart. Unfortunately, these CT findings are usually observed late in the progression of AEF. The appearance of the CT scan early in the course of this complication can be entirely normal. If esophageal injury postablation is suspected, but if the CT scan is normal, the physician must continue to have a high index of suspicion and repeat imaging if symptoms or findings do not resolve. Esophageal ultrasound can also be useful in this setting to disclose muscle and external injury, beyond a simple ulcer. Although a barium swallow can detect a fistula, its sensitivity is low. If an AEF is suspected, endoscopy with air insufflation should be avoided, given that insufflation of the esophagus with air can result in a large air embolus, producing stroke or death. An alternative strategy, which some members of the writing group employ and which appears to have lower risk is to use CO2 instead of air for insufflation in this setting. If CO2 were introduced into the LA, there would be little adverse consequence. The early recognition of an AEF can be missed due to the low awareness of this rare complication. It is important for patients to be educated as to warning signs and to contact their AF ablation center should any suggestive symptoms develop.

Management of Atrial Esophageal Fistula
The management of AEF following catheter ablation for AF includes preventive measures and therapeutic options. If AEF is diagnosed, available therapeutic options are as follows:
surgical repair of the fistula via thoracotomy (combined LA and esophageal repair with an intercostal muscle flap inserted in between to prevent future recanalization of the fistula tract) via thoracotomy;
the less invasive esophageal stenting, followed by long-term antibiotic therapy; and
conservative management with aggressive chest tube drainage and treatment of sepsis.341,417,907,908,909,910,911
Of the above three, conservative treatment of AEF is associated with a high mortality rate.907,1398 Similarly, with esophageal stenting, earlier studies have reported fatality in the majority and survival in very few only after undergoing emergency surgical repair.341,417,896,897,907,910,911,912,913,914,1398 Mixed results have also been shown for surgical repair of AEF complicating RFCA, some with positive outcome and others with fatal ending.341,417,910,911 However, the only reported survival in patients thus far underwent surgical fistula repair, and failure of surgery has been mostly attributed to delay in diagnosis and intervention.341,417,910,911 Thus, based on currently available clinical information, it is apparent that early surgical intervention is critical for survival in AEF manifesting as a complication of AF ablation. Of note, there are few reports on successful resolution of the fistula with stenting in patients with cardioesophageal (connecting to CS) and esophagopericardial fistula.905,915,916 In cases of perforation (not thermal injury) before the fistula has formed, closure with stent or endoscopic clip can be considered.917,918,919

Summary
Although all of the approaches described above for the prevention of AEF have been variously adopted by different ablation centers, each remains largely unproven due to the rarity of an AEF as a complication. Among the writing group members, 67% employ an esophageal temperature probe (single thermocouple for two-thirds, multiple thermocouple for one-third), 36% use 3D image integration and import the esophagus location into the electroanatomical map, 91% decrease RF power when ablating on the posterior wall of the atrium, 7% use barium paste, and none (0%) mechanically displace the esophagus. Among the writing group members, 30% limit power to ≤20 W on the posterior wall, 45% limit it to 25 W, 18% to 30 W, and 7% use powers of >30 W. The writing group recommends that it is reasonable to use an esophageal temperature probe during RF ablation procedures to monitor esophageal temperature and to help guide energy delivery (Class IIa, LOE C-EO, Table 3). The writing group recommends that RF power be reduced when creating lesions along the posterior wall near the esophagus (Class I, LOE C-LD, Table 3).
Despite its rarity, the devastating consequences of AEF demand that the operator maintain a high index of suspicion for this diagnosis. Presenting symptoms, including fever, dysphagia, and neurological deficits, often occur in the several weeks after the procedure.918 Therefore, early signs of these symptoms should be reported by patients to their treating electrophysiologist to avoid the delayed diagnosis.908 If AEF is suspected, standard transesophageal endoscopy should be avoided, because esophageal perforation can be exacerbated and air embolism promoted by required air insufflation. An alternative strategy, which some members of the writing group employ and which appears to have lower risk is to use CO2 instead of air for insufflation in this setting. If CO2 were introduced into the LA, there would be little adverse consequence. In patients diagnosed with an AEF, surgical treatment is recommended.