The purpose of this study is to determine if the use of Circa™ temperature monitoring system during ablation procedures will reduce the risk of esophageal lesions or damage. Esophageal lesions caused by ablation could later develop into a potentially fatal atrio-esophageal fistula, which is hole between the upper chamber of the heart and the esophagus. Although development of atrio-esophageal fistula following atrial fibrillation ablation is extremely rare, the complication is severe and potentially life-threatening. Therefore, monitoring of esophageal temperatures has been adopted to prevent the development of esophageal lesions. The Circa™ temperature monitoring system allows cardiac electrophysiologists to monitor and thereby limit temperatures as well as duration of ablation in the esophagus throughout the procedure.

Dr. Gregory Feld, M.D. is conducting a research study to find out more about the short-term effects on the esophagus of left atrial ablation (guided by Circa™ esophageal temperature monitoring system). The financial supporter of this study is Circa Scientific, LLC.

When the investigators perform a radiofrequency catheter ablation (RFCA) at UCSD, the investigators routinely use the Circa™ temperature monitor system to prevent damage to the esophagus. For this study, patients will receive an esophagoscopy, a procedure in which a flexible tube with a camera is inserted through the mouth into the esophagus. The esophagoscopy will be conducted the next day following the ablation procedure to examine the lining of the esophagus for possible lesions or damage. Patients are asked to participate in this study because they are scheduled to have an ablation for atrial fibrillation (AF). There will be approximately 40 participants in this study at the University of California, San Diego (UCSD) Cardiovascular Center. The use of the Circa™ temperature monitoring system used in standard ablation procedures at UCSD and will be used whether or not patients decide to participate in this study. Using esophagoscopy, this study will evaluate the lining of the esophagus, or swallowing tube between the throat and stomach, the day following atrial fibrillation ablation by using an endoscope, flexible tube equipped with a camera.

Patients enrolled in the study will proceed to their standard of care ablation procedure for treatment of atrial fibrillation. There will be no changes to the ablation as part of this research study. The Circa™ temperature monitor system will be used throughout the ablation as is standard clinical care for all patients receiving AF ablations at UCSD. For research purposes only, patients will undergo an esophagoscopy, or endoscopic evaluation of the esophagus, the next day following the atrial fibrillation ablation. This procedure will take 40-45 minutes, and will involve inserting a flexible probe (tube) with a camera, into the throat and esophagus (swallowing tube), where it will be inspected for any damage (thermal lesions) caused during the ablation procedure.

Following the procedure, patients will be monitored in the usual fashion in the procedure treatment unit (PTU), as is standard of care following AF ablation. Ablation patients will be discharged from the hospital in a standard manner after esophagoscopy and asked to schedule a follow-up appointment following ablation, as is standard of care. There will not be any research follow-up for this study. If for any reason patients cannot complete the ablation or esophagoscopy procedure, patient will be withdrawn from study.

Inclusion Criteria:

• Must have atrial fibrillation and be scheduled for AF ablation, during which the Circa esophageal temperature probe will be used to guide ablation.
• Must give written informed consent

Exclusion Criteria:

• Patient's refusal to participate in the study
• Any known esophageal disease or prior injury that would preclude esophagoscopy
• Any complications occuring during or after AF ablation that would result in esophagoscopy being an added significant risk to the patient beyond the known potential risks from the esophagoscopy
• Prior AF ablation

In two patients in each group of 20 patients originally approved by the IRB for enrollment (total 40 for the study) either the endoscopy could not be performed (2 patients) or the patients declined to undergo endoscopy after the procedure (2 patients). Thus, only 36 patients ended up completing the study and could be included in the data analysis.

Adverse event data were collected for each study participant from the time of ablation through the time of esophagoscopy, which included immediately after ablation in the first phase of the study (18 patients) and 24 hours after ablation in the second phase of the study (18 patients).