Effect of esophageal cooling on ablation lesion formation in the left atrium: Insights from Ablation Index data in the IMPACT trial and clinical outcomes

Abstract

Introduction: The IMPACT study established the role of controlled esophageal cooling in preventing esophageal thermal injury during radiofrequency (RF) ablation for atrial fibrillation (AF). The effect of esophageal cooling on ablation lesion delivery and procedural and patient outcomes had not been previously studied. The objective was to determine the effect of esophageal cooling on the formation of RF lesions, the ability to achieve procedural endpoints, and clinical outcomes.

Methods: Participants in the IMPACT trial underwent AF ablation guided by Ablation Index (30 W at 350-400 AI posteriorly, 40 W at ≥450 AI anteriorly). A blinded 1:1 randomization assigned patients to the use of the ensoETM® device to keep esophageal temperature at 4°C during ablation or standard practice using a single-sensor temperature probe. Ablation parameters and clinical outcomes were analyzed.

Results: Procedural data from 188 patients were analyzed. Procedure and fluoroscopy times were similar, and all pulmonary veins were isolated. First-pass pulmonary vein isolation and reconnection at the end of the waiting period were similar in both randomized groups (51/64 vs. 51/68; p = 0.54 and 5/64 vs. 7/68; p = 0.76, respectively). Posterior wall isolation was also similar: 24/33 versus 27/38; p = 0.88. Ablation effect on tissue, measured in impedance drop, was no different between the two randomized groups: 8.6Ω (IQR: 6-11.8) versus 8.76Ω (IQR: 6-12.2; p = 0.25). Arrhythmia recurrence was similar after 12 months (21.1% vs. 24.1%; 95% CI: 0.38-1.84; HR: 0.83; p = 0.66).

Conclusions: Esophageal cooling has been shown to be effective in reducing ablation-related thermal injury during RF ablation. This protection does not compromise standard procedural endpoints or clinical success at 12 months.

Keywords: AF ablation; Ablation Index; efficacy; efficiency; esophageal cooling.

Figure 1

Collection and processing of Ablation Index data. (A) The posterior line is nearing completion. The operator has moved from point 110 at the left side of the line to a point abutting the right pulmonary vein lesion set, giving a distance of 25 mm between consecutive lesions, although adjacent lesions are <6 mm apart. (B) Data are stored in the CARTO system for each lesion, including a timestamp for the start and end of each delivery and three‐dimensional coordinates for its position. (C) Exported data are analyzed, including calculation of the interval between lesions from the time‐stamps, and calculation of the distance between consecutive points by trigonometry.

Figure 2

Sites of pulmonary vein reconnection. There were 13 reconnections in 11 patients, with one patient in the control group having 2 points of reconnection, one in each circumferential lesion set. Reconnections were all either posterior or carinal.

Figure 3

Scatter plots showing the relationship between AI and impedance drop in the protected and control groups in each location. (A) In the anterior left atrium, the AI values cluster just above the target of 450 for that region. (B) For the posterior PV encirclement lesions, the clustering of AI values is just above 350. (C) In the posterior wall line, the AI values are similar to the posterior PV set. AI, Ablation Index; PV, pulmonary vein.

Figure 4

Scatter plots showing the relationships between interlesion distance and interlesion time (A–C), and interlesion distance and impedance drop (D–F) in the protected and control groups in each location.

Figure 5

Population pyramid frequency plot of the Ablation Index values in the protected and control groups. RF, radiofrequency.

Figure 6

Kaplan–Meier graph of AF or atrial arrhythmia recurrence between the two randomized groups, showing no difference (21.1% vs. 24.1%; 95% CI: 0.38–1.84; HR: 0.83; p = 0.66). AF, atrial fibrillation.