Comparison of ex vivo lesion formation for two adjacent radiofrequency applications with very high-power short-duration in various inter-lesion times

Background/Objectives Very high-power and short-duration (vHPSD) ablation with QDOT MICRO (TM) facilitates speedy and safe ablation for pulmonary vein isolation. A brief time interval between ablating two neighboring sites with vHPSD may potentially influence the size and geometry of the lesions. This study evaluates lesion formation when delivering adjacent applications using vHPSD at various inter-lesion times (ILTs). Methods Radiofrequency applications were conducted by QDOT MICRO (TM) catheter with 90 W of strength and 4 s duration. Fresh swine heart tissue on the epicardium was ablated with 10 g of the contact force. Lesions were created using a single application (SA) and double applications (DA) of adjacent lesions with a 6 mm distance between them as measured on the 3D mapping system. The DA was performed with various ILTs, 60 s (DA-60 s), 10 s (DA-10 s), 5 s (DA-5 s), and 0 s (DA-0 s). Results Out of 90 lesions, 79 were analyzed. Eleven lesions were excluded for one steam pop event, seven out of the target distance, and three divided lesions of two applications. There were no significant differences in surface diameter, cross-sectional diameter, and maximal lesion depth in each application among the groups. The intermediate lesion depth was significantly more profound in groups with shorter and immediate ILT (DA-10, 5, and 0 s) compared to the group with a prolonged ILT between two applications (DA-60 s) (2.99, 3.03, 3.16 mm vs. 2.42 mm, respectively; p < .001). Conclusions Two adjacent radiofrequency applications with vHPSD in short ILT may result in deeper lesions in the middle of combined double lesions.