It's a randomized pilot study to evaluate the incidence of esophageal thermal injury after left atrial ablation for the treatment of atrial fibrillation according to three different strategies of esophageal temperature monitoring.

These patients will be divided into 3 groups with different strategies of esophageal temperature monitoring: group 1 without monitoring, group 2 monitoring with single probe thermometer and group 3 monitoring with multi-probe thermometer.

The primary end point will be the incidence of esophageal lesions assessed by upper endoscopy.

This is a randomized pilot study on the effect of oesophageal temperature monitoring on the esophageal thermal injury after left atrial ablation for the treatment of atrial fibrillation (AF).

Sixty patients with paroxysmal AF or persistent and without previous AF ablation with indication of AF ablation will be selected to be included at the study.

After informed consent, these patients will be randomized in 3 groups with different strategies of esophageal protection for radiofrequency application in the posterior wall of the left atrium, by randomization in a ratio of 1: 1: 1 between groups.

Group I: no esophageal temperature monitoring technique. Group II: monitoring of esophageal temperature during radiofrequency applications in the posterior wall of the left atrium, with unipolar thermometer.

Group III: oesophageal temperature monitoring during radiofrequency applications in the posterior wall of the left atrium, with a multipolar and self expandable thermometer.

The primary end point will be the incidence of esophageal lesions assessed by upper endoscopy that will be done in all patients.

Inclusion Criteria:

• Patients with paroxysmal or persistent AF, diagnosed by electrocardiogram, 24-hour Holter, or monitors of implantable or non-implantable events, with at least one episode of AF up to 12 months before the procedure. Patients should be willing and able to sign an informed consent form, and to undergo all procedures described in both the study protocol and the consent form.

Exclusion Criteria:

• Atrial thrombus in the left atrium, history of AF ablation, history of cardiac surgery, contraindication to anticoagulation, permanent AF, New York Heart Association functional class III or IV, stroke in the last 3 months, pregnancy, history blood clotting abnormalities, previous oesophageal surgery, or advanced chronic kidney disease (creatinine > 2.5 mg/dl).