An initial ex vivo evaluation of temperature profile and thermal injury formation on the epiesophageal surface during radiofrequency ablation

Abstract

Introduction Few studies have examined heat transfer and thermal injury on the epiesophageal surface during radiofrequency application, or compared the risk of esophageal thermal injury between standard and high‐power, short‐duration (HPSD) ablation. We studied the thermodynamics of HPSD and standard ablation at different tissue interfaces between the left atrium and esophagus, focusing on epiesophageal temperature changes and thermal injury. Methods and Results Fresh porcine heart and esophageal sections were secured to a custom holder and submerged in a temperature‐controlled, circulating water bath. During ablation, thermistors recorded temperatures at the catheter tip–atrial interface, epiesophageal–atrial interface, and esophageal lumen. Samples were ablated in triplicate with the following parameters: contact force (15/25g), power (10/20/30 W standard; 40/45/50 W HPSD), and duration (10/20/30 s standard; 5/10/15 s HPSD). Epiesophageal and endoluminal temperature rises were greater in HPSD than in standard ablation (epiesophageal: 5.9 ± 5.6 vs. 2.2 ± 2.0°C, p < .01; endoluminal: 0.7 ± 0.5 vs. 0.4 ± 0.2°C, p < .01). Six of 30 HPSD ablations and 1 of 26 standard ablations caused esophageal injury. The delay between the peak epiesophageal and endoluminal temperatures was greater in HPSD than in standard ablation (24.2 ± 22.1 vs. 13.0 ± 11.0 s, p = .023). Likewise, the peak epiesophageal surface temperature differed more from the concurrent endoluminal temperature in HPSD ablation (5.1 ± 5.3 vs. 1.7 ± 2.0°C, p < .01). Conclusion Endoluminal temperature underestimates epiesophageal surface temperature substantially during HPSD ablation. Visible epiesophageal injury was associated with a 2.2 ± 2.1°C rise in endoluminal temperature, corresponding to a 10.2 ± 6.5°C rise in epiesophageal temperature.

Calculated parameters of luminal esophageal temperatures predict esophageal injury following conventional and high‐power short‐duration radiofrequency pulmonary vein isolation

“…Yavin et al found higher maximal LET in the HPSD group (39.2 ± 2.2°C vs. 38.1 ± 1.1°C) 24 . A study in isolated porcine hearts comparing HPSD to standard protocols also showed significantly higher esophageal (0.7 ± 0.5°C vs. 0.4 ± 0.2°C) and epi‐esophageal (5.9 ± 5.6°C vs. 2.2 ± 2.0°C) temperature rises with HPSD 25 …”

Further mechanistic evidence against luminal esophageal temperature monitoring?

“…To the Editor, We congratulate Kar et al on their elegant and insightful study evaluating ex-vivo temperature profiles and the resulting thermal injury formation on the epiesophageal surface during radiofrequency (RF) ablation. 1 In addition to being the first study to detail temperature profiles inclusive of the epiesophageal surface during RF ablation, we believe that the results add further concern to the use of temperature-sensing technology in the quest to reduce esophageal injury.…”

Procedural time reduction associated with active esophageal cooling during pulmonary vein isolation

“…[17, 18, 21] Proposed mechanisms for this finding involve physical limitations in adequately positioning temperature sensors to detect thermal insults, and inherent limitations in detecting temperature rise before damage has occurred. [3, 4] In contrast, three randomized, controlled studies have demonstrated benefits with active esophageal cooling, with the largest study of 120 patients showing reductions of all lesion formation of 83%, and reductions of severe lesion formation of 100% on per-protocol analysis. [2, 8, 22, 23] Shortening of the procedure time may provide further incentive to transition from a passive monitoring strategy to an active cooling strategy for esophageal protection.…”

“…[2] However, LET often notifies the electrophysiologist after the esophageal temperature has reached dangerous levels—after injury has occurred. [3, 4] Consequently, temperature alarms in ablations that utilize LET can result in frequent pauses to wait for luminal temperature to return to safe levels. These pauses lead to increased procedure times and suboptimal ablations given an increase in the continuity index of each ablation.…”