ABSTRACT
AIMS: The optimal interlesion distance (ILD) for 90 and 50â W 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 90â W-4â s and 50â W applications with low AI values to optimize catheter ablation outcomes in humans. METHODS AND RESULTS: Posterior intercaval lines were created in eight adult sheep using CARTO and the QDOT-MICRO catheter in a temperature-controlled mode. In four animals, the lines were created with 50â W applications, a target AI value ≥350, and ILDs of 6, 5, 4, and 3â mm, respectively. In the other four animals, the lines were created with 90â W-4â s applications and ILDs of 6, 5, 4, and 3â mm, respectively. Activation maps were created immediately after ablation and at 21 days to assess linear block prior to gross and histological analyses. All eight lines appeared transmural and continuous on histology. However, for 50â W-only applications with an ILD of 3â mm resulted in durable linear electrical block, whereas for 90â W applications, only the lines with ILDs of 4 and 3â mm were blocked. No complications were detected during ablation procedures, but all power and ILD combinations except 50â W-6â mm resulted in asymptomatic shallow lung lesions. CONCLUSION: In the intercaval region in sheep, for 50â W applications with an AI value of â¼370, the optimal ILD is 3â mm, whereas for 90â W-4â s applications, the optimal ILD is 3-4â mm.