Radiofrequency ablation—Real‐time visualization of lesions and their correlation with underlying parameters

Background Lesion durability and transmurality are crucial for successful radiofrequency (RF) ablation. This study provides a model of real‐time RF lesion visualization and insights into the role of underlying parameters, as local impedance (LI). Methods A force‐sensing, LI‐sensing catheter was used for lesion creation in an ex vivo model involving cross‐sections of porcine cardiac preparations. During 60 s of RF application, one measurement per second was performed regarding lesion size and available ablation parameters. In total, 1847 measurements from n = 36 lesions were performed. Power (20–50 W) and contact force (1–5 g, 10–15 g, 20–25 g) were systematically alternated. Results Lesion formation was most prominent in the first seconds of RF application during which nonlinear lesion growth was observed (max. 1.08 mm/s for lesion depth and 2.71 mm/s for lesion diameter). Power levels determined the extent of lesion formation in the early phase. After 20 s, lesion size growth velocity approaches 0.1 mm/s at all power levels. LI changes were also highest in the first seconds (up to – 12 Ω/s) and decreased to less than – 0.1Ω/s after prolonged application. Conclusion Lesion formation in irrigated RF ablation is a nonlinear process. Final lesion size resulting from an RF application is mainly influenced by high rates of lesion growth in the first seconds of ablation. LI seems to be a good surrogate for differentiating changes in lesion formation.