In vivo Lesion Index (LSI) validation in percutaneous radiofrequency catheter ablation

Introduction: Lesion Index (LSI) has been developed to predict lesion efficacy during radiofrequency (RF) catheter ablation. However, its value in predicting lesions size has still to be established. The aim of our study was to assess the lesions size reproducibility for pre-specified values of LSI reached during RF delivery in an in vivo beating heart. Methods: Ablation lesions were created with different values of LSI in 7 domestic pigs by means of a contact force sensing catheter (TactiCathTM , Abbott). Lesions were identified during RF delivery by means of a 3D mapping system (EnSiteTM Precision, Abbott) and measured after heart explantation. Histology was carried out after gross examination on the first 3 lesions to confirm the accuracy of the macroscopic evaluation. Results: A total of 64 myocardial lesions were created. Thirty-nine lesions were excluded from the analysis for the following reasons: histological confirmation of macroscopic lesion measurement (n=3), transmurality (n=24), unfavorable anatomic position (n=10), not macroscopically identifiable (n=2). In a final set of 25 non-transmural lesions, injury width and depth were respectively 4.6±0.6 mm and 2.6±0.8 mm for LSI=4, 7.3±0.8 mm and 4.7±0.6 mm for LSI=5, and 8.6±1.2 mm and 7.2±1.1 mm for LSI=6. A strong linear correlation was observed between LSI and lesion width (r=0.87, p<0.00001) and depth (r=0.89, p<0.00001). Multiple linear regression analysis identified LSI as the only ablation parameter that significantly predicted lesion width (p<0.001) and depth (p<0.001). Conclusion: In our in vivo study, LSI proved highly predictive of lesion size and depth.