Evaluation of force time integral, force time current integral and lesion size index in a new force sensing catheter

FUNDING ACKNOWLEDGEMENTS: Type of funding sources: None. BACKGROUND: Radiofrequency current remains one of the most important ablation techniques in the EP lab. Creating durable lesions is key to successful ablation. Evaluating lesion quality and progression of lesion growth is difficult as many parameters influence lesion formation. Therefore, several approaches were developed, as monitoring RF duration, power and contact force seems insufficient in clinical practice. Force-time-integral (FTI) and force-time-current-integral (FTCI), as well as the ablation index (AI) and lesion size index (LSI) showed decent results in past studies. Recently, a new force sensing catheter (NFSC) was released. By now, data about lesion formation and correlation with the FTI, FTCI and LSI is lacking with this NFSC. This study aimed to further investigate lesion formation with the NFSC in an ex vivo model. METHODS: 30 RF-lesions were created using an ex vivo porcine cardiac model with the NFSC catheter. The experimental setup consisted of a saline-filled container, a dispersive electrode, a heated thermostat and a circulation pump to imitate in vivo conditions. Global impedance was kept at 120 Ohm as well as the temperature at 37°C. In a first set of lesions, CF was varied (1g, 5g, 10g, 20g). Three lesions were created in each CF-level with 30W. In a second set of lesion, CF was kept at 10 – 15 g, but ablation power was set to 20W, 30W, 40W, 50W, 60W and 70W. In every power level, three lesions were created. All parameters (power, temperature, global impedance, contact force, lesion size) were measured constantly during application of RF-current, enabling real-time correlation of RF parameters and lesion size. In case of an audible steam pop, RF application was stopped. RESULTS: 1640 measurement in 30 lesions were included into the analysis. Mean lesion diameter was 7.82 ± 1.52 mm, mean lesion depth 4.80 ± 1.08 mm. Baseline global impedance (GI) was 138.10 ± 10.93 Ω, mean GI-drop 28.10 ± 8.00 Ω. In average, CF of 12.10 ± 5.87 g was used. Correlations of lesion size, FTI and FTCI are shown in table 1. Interestingly, LSI correlated best with lesion size (r = 0.851 and r = 0.852 for lesion depth and diameter; p<0.001). Figure 1 illustrates a scatter plot of LSI and lesion depth (Figure 1a) and lesion diameter (Figure 1b). Figure 2 shows dynamic changes in lesion depth compared to changes in LSI and FTCI. During RF-application, development of lesion formation and LSI is comparable from approximately second 7 onwards. FTCI is rising in a linear manner, whereas lesion formation increases monoexponentially. CONCLUSION: In the NFSC, lesion size correlates strongest with the LSI in power levels up to 70 Watts. FTI and FTCI also showed decent correlations. Regarding dynamic changes in lesion size, LSI is best comparable to actual lesion growth. [Figure: see text] [Figure: see text]