Abstract and Introduction
Esophageal injury is a rare but serious complication of catheter ablation for atrial fibrillation using radiofrequency energy. Recent studies have begun to identify variables that may determine heat transfer to and thermal injury of the esophagus. There is significant variability in the relationship between the esophagus and left atrium among individuals. New imaging techniques can facilitate assessment of esophagus position relative to intended ablation targets. Strategies to minimize the risk of esophageal injury include avoidance of ablation near the esophagus, titration of RF energy delivery at the posterior left atrial endocardium, and the use of alternative ablation methods.
Atrioesophageal fistula was first reported as a fatal complication of endocardial surgical radiofrequency (RF) ablation for atrial fibrillation (AF), and has since been reported after percutaneous endocardial RF catheter ablation for AF (catheter ablation).[2,3] The incidence of atrioesophageal fistula after catheter ablation is estimated to be between 0.03% and 0.5%; however, underreporting is likely, and the true incidence is unknown. A recent report of 28 patients undergoing esophagogastroscopy 24 hours after catheter ablation revealed that 47% of patients had esophageal mucosal changes consistent with thermal injury and 18% demonstrated necrotic or ulcer-like changes. In this study, left atrial RF lesions were delivered without regard to the location of the esophagus. Thus, there is clear potential to produce transmural esophageal injury during catheter ablation for AF when employing a lesion set targeting the posterior left atrial wall and pulmonary vein (PV) antra using contemporary large-tip or irrigated-tip catheter ablation systems when endocardial target sites are in close proximity to the esophagus.
Atrioesophageal fistula after catheter ablation is thought to occur due to conductive heat transfer to the esophagus[7,8] that causes transmural tissue necrosis, mediastinitis, and a fistulous connection between the esophageal lumen and the left atrial blood pool. This can lead to sepsis and stroke. Other mechanisms of esophageal injury resulting from injury to the esophageal blood supply, or to the nerves and nerve plexi on the surface of the esophagus, have not been excluded. Though incompletely described, factors that likely determine heat transfer to the esophagus during catheter ablation include the magnitude and duration of local tissue heating, which is related to the total ablation energy delivered to cardiac tissue at an ablation site near the esophagus. Catheter tip size, contact pressure, and catheter orientation are important variables that determine what percentage of applied RF energy is actually delivered to cardiac tissue. Heat transfer to the esophagus is also dependent on atrial tissue thickness, and the thickness and character of intervening connective tissue including adipose tissue between the heart and esophagus,[8,11,12] which together determine the minimum possible distance between an ablation site at the posterior left atrial endocardium and the esophagus and the rates of heat conduction through tissue to the esophagus. Cadeveric and computed tomography (CT) studies of humans suggest that the connective tissue layer between the posterior LA wall and esophagus varies significantly in thickness between individuals, and also at different rostral-caudal levels of the esophagus-atrial contact region in the same patient.[13,14,15] Further, the thickness of the PV wall and PV antrum has been described to be as little as 2-3 mm, much thinner than atrial myocardium at the posterior or anterior free walls. Together, these observations suggest that heat transfer to the esophagus may be enhanced during RF ablation near the vein ostia if the esophagus is located adjacent to these regions, especially when coupling between ablation catheter and tissue is optimal for RF energy transfer, and when intervening tissue between heart and esophagus is minimal or absent. Indeed, an initial report of atrioesophageal fistulae after catheter ablation described fistula formation in the region of the posterior left PV antrum near the left superior PV os. Other factors could influence progression of esophageal injury to fistulae after RF ablation, such as inflammation or acid reflux; however, the respective roles of these or other variables are as yet unknown. Some centers routinely use proton pump inhibitors or other antacid or antireflux therapies such as sucralfate after catheter ablation; however, evidence is lacking regarding whether these therapies prevent progression of thermal esophageal injury to fistula formation.
Pacing Clin Electrophysiol. 2009;32(2):248-260. © 2009 Blackwell Publishing
Cite this: Strategies to Minimize the Risk of Esophageal Injury During Catheter Ablation for Atrial Fibrillation - Medscape - Feb 01, 2009.