DISCUSSION
AEF is a relatively rare condition that is often life-threatening. Despite significant refinement in surgical techniques, the operative mortality of open repair ranges from 25% to 100%.1-3There are several etiologies of primary AEF including thoracic aortic aneurysm, foreign body ingestion, esophageal malignancy, and prolonged gastric intubation.6,7 There are several etiologies of secondary AEF resulting from surgery in the posterior mediastinum such as aortic arch replacement, TEVAR to descending aorta, and esophageal surgery. 4,8 The number of secondary AEF is increasing due to increase in the number of TEVAR being performed. Treatment of secondary AEF can be more challenging than that of primary AEF due to the presence of adhesion in the pleural space and the poor general status of patients. In the patients in this study who underwent combined repair, reconstruction of the aorta and esophagus could not be completed due to severe adhesions caused by previous TEVAR. There have been few studies comparing the degree of adhesion between post-TEVAR cases and post-graft replacement cases. Moreover, there have been few studies regarding outcomes between post-TEVAR and post-graft replacement in secondary AEF cases. Further studies are warranted, however, according to the present study, secondary AEF after TEVAR can be more critical than secondary AEF after graft replacement.
The exact mechanism of secondary AEF after TEVAR remains unknown. Eggebrecht et al. reported that the incidence of AEF was 1.9% and occurred 1–16 months following intervention in a series of 268 patients who underwent TEVAR.5 Some reports suggested that its pathogenesis was related to inflammation of the aneurysmal wall.9,10 They also suggested that the pathogenesis was related to esophageal ischemia secondary to elevated pressure in the posterior mediastinum, inflammation due to the resorbed hematoma, and mechanical compression by a large aneurysm following TEVAR.9,10 In post-TEVAR cases, fistulas were reportedly caused by endoleaks into the residual aneurysmal sac, erosion of the stent-graft through the aorta, and ischemic necrosis of the esophageal wall due to compression of its feeding arteries by the stent-graft.4,5 In accordance with these reports, severe adhesion between the descending aorta and esophagus might occur more frequently in secondary AEF after TEVAR than after graft replacement. In aortic rupture cases, endovascular stenting does not remove the hematoma or the thrombosis, and thoracic compartment syndrome is likely to occur. Therefore, emergency TEVAR is associated with an increased risk of AEF occurrence.4,5,11 In the present study, in three (75%) patients who had undergone TEVAR previously, AEF developed after emergency TEVAR.
It has been previously reported that aggressive treatment for patients with AEF was associated with good outcomes5,10,12 and reduced short-term mortality. In the present study, although patients who received open surgical repair were hospitalized for a longer period, they were discharged without complications. However, the patients who underwent TEVAR alone were also discharged without complications. The treatment strategy should be carefully decided especially in patients with secondary AEF. In severely deteriorated cases, palliative treatment can be considered as an alternative.
Although TEVAR was proposed as an alternative surgical management strategy for open surgery,13 secondary AEF after TEVAR can have severe consequences when left untreated.4,5With the increasing numbers of TEVAR procedures being performed and the longer follow-up periods, late complications of TEVAR are becoming increasingly evident.4,5 The treatment strategy for secondary AEF after TEVAR should be carefully designed considering the presence of severe adhesions between the aorta and esophagus. Moreover, the patient’s frailty should be considered in the decision of treatment. Further studies on surgical treatment for secondary AEF cases, especially regarding patient inclusion and exclusion criteria are warranted.
This study had several limitations. First, a small number of patients was included owing to the rarity of secondary AEF. Therefore, accurate evaluation might be difficult because combined surgery was performed on severely ill patients. Second, it was a retrospective study and the data were obtained from a single institution. Therefore, the study results may not reflect the general features of patients with AEF. Third, endovascular treatment strategy has evolved during the time period of this study.