Prospective Validation to Predict Radiofrequency Lesion Size During High-Power and Short-Duration Ablation Using a Novel Index Formula Incorporating Contact Force, Radiofrequency Power and Application Time in a Swine Beating Heart Model

BackgroundDuring radiofrequency (RF) ablation, lesion size increases with increasing contact force (CF), RF power and application time. The effects of CF and RF power on lesion size during high-power and short-duration (HP-SD) ablation have not been well-determined. This study aimed to, during HP-SD ablation: 1) examine the relationship between lesion size and CF, RF power and time, and 2) prospectively validate the ability of a novel logarithmic formula, incorporating CF, RF power and time (Force-Power-Time-Index, FPTI, gram x Watt x sec) to predict lesion size using a swine beating heart model. MethodsEight closed-chest swine were studied. A 7.5Fr CF ablation catheter with a 3.5mm irrigated-tip electrode containing 6 surface thermocouples (Qdot-Micro) was positioned in the right and left ventricles. In five swine (Phase1-Study), RF was delivered at [&le;]90Watts (modulated to maintain the surface electrode temperature<65{degrees}C) for 4sec to 103 ventricular sites with various CF (range 5-54g). Swine were sacrificed and lesion size was measured. A new logarithmic FPTI-Formula was created based on the relationship between lesion depth and CF, power and time. In the prospective validation study using the remaining three swine (Phase2-Study), RF(90W) was delivered for 4 sec at 72 sites with FPTI-Formula predicted lesion depths of 2-6mm. Actual lesion depth was compared to the predicted lesion depth. ResultsIn the Phase1-study, there was a close relationship between lesion depth and the product of Force x Power x Time (R=0.711, p<0.0001), creating a novel logarithmic FPTI-Formula to predict lesion depth. In the Phase2-study, lesion depth predicted by the FPTI-Formula correlated highly with actual lesion depth (1.9-6.1mm), with {+/-}1mm accuracy in 68/72(94%) lesions (R=0.867, p<0.0001). No steam pop or thrombus formation occurred. ConclusionDuring HP-SD ablation, the new FPTI-Formula prospectively predicted lesion depth with high accuracy while the surface electrode temperature control prevented steam pop and thrombus formation.