Ablation of atrial fibrillation and esophageal injury: Effects of energy source and ablation technique

Objective: The aim of this study was the evaluation of histologic changes induced on the esophagus by surgical ablation therapy for atrial fibrillation. Methods: Experiments were performed on 39 sheep. Circular lesions were created endocardially or epicardially in the left atrium and at the pulmonary veins by using different energy sources: cryoablation, microwave, laser, and unipolar or bipolar radiofrequency. Temperatures inside the esophagus were measured, and esophageal tissue was investigated macroscopically and histopathologically. Results: Esophageal damage was seen histologically in 24 of 39 cases. The epithelium was intact in all cases. Unipolar radiofrequency induced the most intensive esophageal lesions in 4 of 6 cases. The affected areas were small (1.56 - 3.01 mm) but reached deep into the tissue. Endocardial cryoablation resulted in wider lesions (2.01 - 8.54 mm), which were intensive in only 2 of 6 cases. Epicardial cryoablation and bipolar radiofrequency induced wide (1.11 - 6.8 mm) but mainly mild alterations. Endocardial and epicardial microwave energy affected the esophagus in single cases, and lesions were small (0.97 - 2.81 mm). Only in 1 case did laser energy induce a moderate alteration (5.30 mm) of the esophageal wall. Conclusions: Esophageal alterations were found in numerous cases. However, marked lesions were especially induced by endocardial unipolar radiofrequency and cryoablation.