Evaluating Temperature Gradients Across the Posterior Left Atrium with Radiofrequency Ablation.

INTRODUCTION: Esophageal injury is a well-known complication associated with catheter ablation. Though novel methods to mitigate esophageal injury have been developed, few studies have evaluated temperature gradients with catheter ablation across the posterior wall of the left atrium, interstitium and esophagus.

METHODS: To investigate temperature gradients across tissue, we developed a porcine heart-esophageal model to perform ex vivo catheter ablation on the posterior wall of the LA, with juxtaposed interstitial tissue and esophagus. Circulating saline (5 L/min) was used to mimic blood flow along the LA and alteration of ionic content to modulate impedance. Thermistors along the region of interest were used to analyze temperature gradients. Varying time and power, radiofrequency (RF) ablation lesions were applied with an externally irrigated ablation catheter. Ablation strategies were divided into standard approaches (SA, 10-15g, 25-35W, 30s) or high-power short duration (HPSD, 10-15g, 40-50W, 10s). Temperature gradients, time to maximum measured temperature and the relationship between measured temperature as a function of distance from the site of ablation were analyzed.

RESULTS: In total, 5 experiments were conducted each utilizing new porcine posterior LA wall-esophageal specimens for RF ablation (n=60 lesions each for SA and HPSD). For both SA and HPSD, maximum temperature rise from baseline was markedly higher at the anterior wall (AW) of the esophagus compared to the esophageal lumen (SA: 4.29°C vs. 0.41°C, p<0.0001 and HPSD: 3.13°C vs. 0.28°C, p<0.0001). Across ablation strategies, the average temperature rise at the anterior wall of the esophagus was significantly higher with SA relative to HPSD ablation (4.29°C vs. 3.13°C, p=0.01). From start of ablation, the average time to reach maximum temperature as measured at the anterior wall of the esophagus with SA was 36.49 +/- 12.12 sec, compared to 16.57 +/- 4.54 sec with HPSD ablation, p<0.0001. Fit to a linear scale, a 0.37°C drop in temperature was seen for every 1 cm increase in distance from the site of ablation and thermistor location at the anterior wall of the esophagus.

CONCLUSION: Both SA and HPSD ablation strategies resulted in markedly higher temperatures measured at the anterior wall of the esophagus compared to the esophageal lumen, raising concern about the value of clinical intraluminal temperature monitoring. The temperature rise at the anterior wall was lower with HPSD. Significant time delay was seen to reach maximum measured temperature and a modest increase in distance between site of ablation and thermistor location impacted accuracy of monitored temperatures. This article is protected by copyright. All rights reserved.