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
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Background
During 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.
Methods
Eight 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 ≤90Watts (modulated to maintain the surface electrode temperature<65°C) for 4sec to 103 ventricular sites with various CF (range 5-54 g ). 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.
Results
In 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.
Conclusion
During 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.
