AB-453068-4 BENCH EVALUATION OF OVERLAPPING LESION STEAM POP RATES

Abstract

Sequentially delivered, overlapping radiofrequency (RF) ablation lesions pose a risk of creating steam pops due to heat stacking. The relationship between inter-lesion distance and heat stacking is presently unknown. Therefore, the smallest inter-lesion distance for safe therapy delivery needs to be determined. The study objective was to quantify steam pop rates when creating sequential, adjacent, potentially overlapping RF ablation lesions at various inter-lesion distances in a non-perfused bovine cardiac tissue model with the intention of identifying the safest minimum inter-lesion distance. In a saline filled tank at clinically relevant conductivity and temperature, a TactiCath SE RF ablation catheter created sets of 2 lesions on isolated, non-perfused bovine right ventricular tissue. At 15g force and 40W, successive 10s lesions were created (transition time less than 1s between lesions) at center-to-center distances of 1, 2, 3, 4, 5, and 10 mm, and steam pop frequency was determined. If a steam pop occurred during the first 10s lesion prior to the drag, the trial was excluded and repeated. Using pilot data, it was determined a minimum of 49 samples at each inter-lesion distance would provide a robust sample size for statistical analysis. Steam pop rate at an inter-lesion distance of 10mm was used as the control for analysis as there was no lesion overlap at this center-to-center distance. Steam pop rates at 1 and 2 mm were significantly greater (p=0.002 and p<0.001) than at 10mm. Using a 2-proportions, 2-sample non-inferiority (NI) test, with a NI margin of 20%, statistical equivalence was claimed between steam pop rates at 10mm and 5mm (p=0.009), 4mm (p=0.005), 3mm (p=0.003). Lesions spaced closer than 3mm apart have a greater risk of resulting in steam pops. Therefore, a minimum of 3mm inter-lesion distance would be recommended as it has shown to have a similar steam pop rate to focal lesions.