High-Resolution Infrared Thermography of Esophageal Temperature During Radiofrequency Ablation of Atrial Fibrillation.

BACKGROUND: Catheter ablation for atrial fibrillation has potential to cause esophageal thermal injury. Esophageal temperature monitoring during ablation is commonly used; however, it has not eliminated thermal injuries, possibly because conventional sensors have poor spatial sampling and response characteristics. To enhance understanding of temperature dynamics that may underlie esophageal injury, we tested a high-resolution, intrabody, infrared thermography catheter to continuously image esophageal temperatures during ablation. METHODS AND RESULTS: Atrial fibrillation ablation patients were instrumented with a flexible, 9F infrared temperature catheter inserted nasally (n=8) or orally (n=8) into the esophagus adjacent to the left atrium. Ablation was performed while the infrared catheter continuously recorded surface temperatures from 7680 points per second circumferentially over a 6-cm length of esophagus. Physicians were blinded to temperature data. Endoscopy was performed within 24 hours to document esophageal injury. Thermal imaging showed that most patients (10/16) experienced >= 1 events where peak esophageal temperature was >40 degrees C. Three patients experienced temperatures >50 degrees C; and 1 experienced >60 degrees C. Analysis of temperature data for each subject's maximum thermal event revealed high gradients (2.3 +/- 1.4 degrees C/mm) and rates of change (1.5 +/- 1.3 degrees C/s) with an average length of esophageal involvement of 11.0 +/- 5.4 mm. Endoscopy identified 3 distinct thermal lesions, all in patients with temperatures >50 degrees C; all resolved within 2 weeks. CONCLUSIONS: Infrared thermography provided dynamic, high-resolution mapping of esophageal temperatures during cardiac ablation. Esophageal thermal injury occurred with temperatures >50 degrees C and was associated with large spatiotemporal gradients. Additional studies are warranted to determine the relationships between thermal parameters and esophageal injury.