Abstract 16231: Improved Accuracy of Electrical Coupling Index in Predicting Radiofrequency Lesion Size by Using a Smaller Irrigated Ablation Electrode
Introduction: Electrical Coupling Index (ECI, EnSite Contact System, St. Jude Medical, SJM) has been used as a measure of electrode-tissue contact for RF ablation. We postulated that the sensitivity of ECI would be enhanced by using a shorter 2.5 mm ablation electrode due to the decrease in the electrode-blood interface area without changing the electrode-tissue interface area. The purpose of this study was to compare the relationship of ECI and initial impedance to RF lesion size between a 7Fr, 2.5 mm irrigated (Irg) electrode (Gen 2, SJM) and a 7Fr, 4 mm Irg electrode (CoolFlex, SJM).
Methods: Five dogs were studied closed chest. The 2.5 mm and 4 mm Irg electrode catheters were positioned in RV and LV under fluoroscopy. RF energy was delivered with each catheter at 3 sites in RV and at 3 sites in LV for 60 sec (2.5 mm electrode - 15 W in RV, 25 W in LV, 17 ml/min Irg; and 4 mm electrode - 30 W in RV, 50W in LV, 17 ml/min Irg) using a wide range of ECI: 1) 2.5 mm electrode ECI 119 - 461 (median 270); and 2) 4 mm electrode ECI 72 - 328 (median 149). Lower RF power was used with the 2.5 mm electrode due to less loss of power to the blood pool (smaller electrode-blood interface area), producing similar lesion depth. Dogs were sacrificed at 1 hour and lesion size was measured using TTC staining.
Results: At constant RF power and time, lesion depth increased significantly with increasing ECI for both 2.5 mm and 4 mm electrodes (Figs A-D). Compared to 4 mm, 2.5 mm electrode had better correlation between ECI and lesion depth (R=0.94 vs 0.81 in RV and R=0.89 vs 0.76 in LV). Steam pop occurred only with very high ECI (≥352 for 2.5 mm electrode or 306 for 4 mm electrode). There was poor correlation between the initial impedance and lesion depth.
Conclusions: At the same RF power, lesion depth increases significantly with increasing ECI. The smaller electrode (2.5 mm) increases the range of ECI and significantly improves the relationship between ECI and RF lesion size. Steam pop occurs only at very high ECI.
- © 2012 by American Heart Association, Inc.