Optimal Interlesion Distance for 90- and 50-Watt Radiofrequency Applications with low Ablation Index Values: Experimental Findings in a Chronic Ovine Model.

AIMS: The optimal interlesion distance (ILD) for 90 and 50W radiofrequency applications with low ablation index (AI) values in the atria has not been established. Excessive ILDs can predispose to interlesion gaps whereas restrictive ILDs can predispose to procedural complications.The present study sought, therefore, to experimentally determine the optimal ILD for 90W-4 sec and 50W applications with low AI values to optimize catheter ablation outcomes in humans.

METHODS AND RESULTS: Posterior intercaval lines were created in 8 adult sheep using CARTO and the QDOT-MICRO catheter in a temperature-controlled mode. In 4 animals the lines were created with 50W applications; a target AI value ≥350; and ILDs of 6, 5, 4 and 3 mm, respectively. In the other 4 animals the lines were created with 90W-4 sec applications and ILDs of 6, 5, 4 and 3 mm, respectively. Activation maps were created immediately after ablation and at 21 days to assess linear block prior to gross and histological analyses.All 8 lines appeared transmural and continuous on histology. However, for 50W only applications with an ILD of 3 mm resulted in durable linear electrical block, whereas for 90W applications only the lines with ILDs of 4 and 3 mm were blocked. No complications were detected during ablation procedures but all power and ILD combinations except 50W-6 mm resulted in asymptomatic shallow lung lesions.

CONCLUSION: In the intercaval region in sheep, for 50W applications with an AI value of ∼370 the optimal ILD is 3 mm, whereas for 90W-4 sec applications the optimal ILD is 3-4 mm.