Characteristics of tissue temperature during ablation with THERMOCOOL SMARTTOUCH SF versus TactiCath versus QDOT MICRO catheters (Qmode and Qmode+): An in vivo porcine study

Abstract

Introduction: High-power short-duration (HPSD) ablation at 50 W, guided by ablation index (AI) or lesion size index (LSI), and a 90 W/4 s very HSPD (vHPSD) setting are available for atrial fibrillation (AF) treatment. Yet, tissue temperatures during ablation with different catheters around venoatrial junction and collateral tissues remain unclear.

Methods: In this porcine study, we surgically implanted thermocouples on the epicardium near the superior vena cava (SVC), right pulmonary vein, and esophagus close to the inferior vena cava. We then compared tissue temperatures during 50W-HPSD guided by AI 400 or LSI 5.0, and 90 W/4 s-vHPSD ablation using THERMOCOOL SMARTTOUCH SF (STSF), TactiCath ablation catheter, sensor enabled (TacthCath), and QDOT MICRO (Qmode and Qmode+ settings) catheters.

Results: STSF produced the highest maximum tissue temperature (T_max ), followed by TactiCath, and QDOT MICRO in Qmode and Qmode+ (62.7 ± 12.5°C, 58.0 ± 10.1°C, 50.0 ± 12.1°C, and 49.2 ± 8.4°C, respectively; p = .005), achieving effective transmural lesions. Time to lethal tissue temperature ≥50°C (t-T ≥ 50°C) was fastest in Qmode+, followed by TacthCath, STSF, and Qmode (4.3 ± 2.5, 6.4 ± 1.9, 7.1 ± 2.8, and 7.7 ± 3.1 s, respectively; p < .001). The catheter tip-to-thermocouple distance for lethal temperature (indicating lesion depth) from receiver operating characteristic curve analysis was deepest in STSF at 5.2 mm, followed by Qmode at 4.3 mm, Qmode+ at 3.1 mm, and TactiCath at 2.8 mm. Ablation at the SVC near the phrenic nerve led to sudden injury at t-T ≥ 50°C in all four settings. The esophageal adventitia injury was least deep with Qmode+ ablation (0.4 ± 0.1 vs. 0.8 ± 0.4 mm for Qmode, 0.9 ± 0.3 mm for TactiCath, and 1.1 ± 0.5 mm for STSF, respectively; p = .005), correlating with T_max .

Conclusion: This study revealed distinct tissue temperature patterns during HSPD and vHPSD ablations with the three catheters, affecting lesion effectiveness and collateral damage based on T_max and/or t-T ≥ 50°C. These findings provide key insights into the safety and efficacy of AF ablation with these four settings.

Keywords: atrial fibrillation; catheter ablation; esophageal injury; phrenic nerve injury; tissue temperature.