A device for protecting the esophagus during a surgical ablation procedure within a heart of a patient comprises a catheter having a sensor (20, 60, 79, 80, 90) and positionable within an esophagus of a patient. An indicator (30, 62, 82, 106) is in communication with the sensor to indicate if a parameter exceeds a predetermined value, thereby indicating to the user to reduce or cease the ablation procedure within the heart of the patient.