Different tissue thermodynamics between the 40 W and 20 W radiofrequency power settings under the same ablation index/lesion size index.

Introduction: The ablation index (AI) and lesion size index (LSI) are novel markers for predicting the ablation lesion quality, however, collateral damage is still a concern. This study aimed to compare the lesion characteristics and tissue temperature profiles between 20 W (20 Ws) and 40 W (40 Ws) ablation settings under the same AI and LSI.

Methods: An ex vivo model consisting of swine myocardium (5-6 mm thickness) in a circulating, warmed saline bath was used. Twenty-one tissue temperature electrodes were used. Radiofrequency applications with different power settings were performed with a 10 to 12 g contact force until the AI and LSI reached 350 and 4.5, respectively.

Results: A total of 120 radiofrequency (RF) applications and 2520 tissue temperature profiles were analyzed. The speed of the tissue temperature rise with 40 Ws was significantly faster than that with 20 Ws. However, the maximum tissue temperature did not significantly differ between 20 and 40 Ws with the same AI (44.6°C ± 3.9°C vs 45.1°C ± 6.4°C, P = .73), and was significantly lower for 40 Ws with the same LSI (42.8°C ± 3.4°C vs 40.0°C ± 3.4°C, P = .003). For both the AI and LSI, the number of electrodes exhibiting high temperatures (≥39°C) was significantly larger and the duration of high tissue temperatures was significantly longer with 20 Ws. The thermal latency with 40 Ws was greater.

Conclusions: Although the targeted AI and LSI were the same for both 20 and 40 Ws, the tissue temperature profiles differed greatly depending on the RF power setting. A high power setting based on the AI and LSI may reduce the collateral thermal damage.