Introduction: Cardiac ablation for atrial fibrillation has the potential to cause esophageal thermal injury. Thermocouple and thermistor-based systems are commonly used to monitor esophageal temperature at one or a few discrete locations, however, these systems have not eliminated thermal injuries and employ thresholds that are considerably lower than well-established temperatures required for irreversible tissue damage.
Hypothesis: To mitigate esophageal thermal injury we modulated delivery of cardiac ablation energy using temperatures obtained from a high-resolution, intra-body, infrared thermography catheter that images esophageal temperatures.
Methods: Esophageal temperatures were recorded from 28 patients undergoing pulmonary vein isolation using RF energy. An infrared catheter recorded surface temperatures from 7,680 points per second over a 6 cm length of esophagus. Physicians used a stepwise approach to set an esophageal temperature threshold. For initial cases a cutoff of 46°C was used and for subsequent cases the threshold was raised to a maximum value of 50°C. Full endoscopy was performed 1 to 3 days after the ablation procedure to document and quantify esophageal injury.
Results: Posterior wall ablation resulted in 196 thermal elevations >40°C (mean 7.0±4.2) and nearly all patients (27/28) experienced a peak esophageal temperature (Tpeak) >40°C. Eight patients experienced Tpeak>50°C; with a maximum recorded Tpeak=53°C. Tpeak exceeded the programmed infrared temperature threshold in 12/28 patients. All patients received a full endoscopy. None of these temperature excursions resulted in visible thermal esophageal injury.
Conclusions: Infrared thermography provided comprehensive monitoring of esophageal temperatures during ablation. By conventional metrics (e.g. Temperature>40°C) a large number of thermal elevations were documented. However, infrared imaging provided instantaneous temperatures that allowed for limited interruption of ablation while preserving esophageal tissue integrity.