Computational method to predict esophageal temperature elevations during pulmonary vein isolation

Background: The esophagus is in close proximity to the posterior wall of the left atrium, which renders it susceptible to thermal injury during radiofrequency (RF) ablation procedures for atrial fibrillation (AF). Real-time assessment of esophageal position and temperature (T°) during pulmonary vein (PV) isolation has not been extensively explored.

Objective: To develop a protocol that allows estimation of the potential for, and avoidance of, esophageal heating.

Methods: In consecutive patients who underwent PV isolation, a thermal probe was used to monitor T° fluctuations in the esophagus during application of RF energy. The tip of the thermal probe was positioned at the level of the targeted PV and RF was discontinued for T° rise >0.5°C. The proximity of individual PVs to the esophagus was measured from the temperature probe tip to the closest posterior part of the Lasso catheter from review of biplane projections (left anterior oblique 60° and right anterior oblique 30°). These raw distances were entered into the Pythagorean theorem and the actual distance between the esophageal thermal probe and PV antrum was determined.

Results: The study cohort included 44 patients (60 ± 11 years, 61% male, 57% lone AF). The thermal probe in the esophagus was closer to the left-sided PVs (left common pulmonary vein: 20.9 ± 13 mm, left upper pulmonary vein: 20.5 ± 11 mm, left lower pulmonary vein: 23.4 ± 10 mm) than the right-sided ones (right common pulmonary vein: 31.0 ± 11 mm, right upper pulmonary vein: 41.9 ± 18 mm, right lower pulmonary vein: 34.5 ± 16 mm). A T° increase >0.5° C occurred during 116/1,495 (7.8%) deliveries. A T° rise was more likely during ablation of left-sided PVs than right-sided PVs (55% vs 10%, P < 0.0001) and when RF was delivered ≤ 24 mm from the esophagus (sensitivity 91%, specificity 81%, positive predictive value 75%, and negative predictive value 93%).

Conclusion: A thermal probe placed in the esophagus provides real-time T° monitoring and anatomic localization. A T° rise is more likely during ablation of left PVs and during RF deliveries within 24 mm of the esophageal thermal probe.