Abstract 13201: Optimal Combination of Power and Application Time to Produce Deeper Radiofrequency Lesions without Steam Pop
Introduction: Cooling an ablation electrode by saline irrigation (IR) prevents thrombus formation and impedance rise, but high RF power often produces tissue overheating and steam pop (a major cause of cardiac perforation during ablation). The purpose of this study was to determine the relationship between RF power, application time and lesion depth which would not produce a steam pop using a canine thigh muscle preparation.
Methods: In 10 dogs, the skin over the thigh muscle was incised and raised to form a cradle which was superfused with heparinized blood at 37 °C. A 7.5 Fr, 3.5mm catheter tip electrode with 56 irrigation holes (ThermoCool SF, Biosense Webster) was held parallel to the thigh muscle at 10 g contact weight. RF current was delivered (n=144) for 20, 30, 40, 50 or 60 sec at constant power of 20 W (IR: 8 ml/min), 30 W (IR: 8 ml/min), 40 W (IR: 15 ml/min) or 50 W (IR: 15 ml/min) in low blood flow (<0.1 m/sec) to favor thrombus. Electrode temperature, electrode-tissue interface temperature and tissue temperatures (3 mm and 7 mm depths) were measured. After each RF, blood was removed from the cradle to examine for thrombus.
Results: Fig. Lesion depth and tissue temperatures increased significantly with increasing RF power and/or application time. Steam pop occurred only at high RF power: 40 W with >40 sec (10/36) and 50 W with >20 sec application times (14/36). 50 W - 20 sec RF applications resulted in shallow lesions (6.2 ± 0.6 mm) with high incidence of steam pop (2/6, 33%). In contrast, 30 W - 60 sec RF applications produced deeper RF lesions (7.9 ± 0.2 mm) without steam pop. Small thrombus (<1mm≥) occurred only with 40 W and 50 W applications.
Conclusions: In the power and time range tested, RF applications with moderate power (30 W) and long application time (60 sec) produced deep lesions (8 mm) without steam pop. High RF power (50 W) and short application times (10–20 sec) were associated with the risk of steam pop, while producing shallower RF lesions (6 mm).
- © 2010 by American Heart Association, Inc.