Abstract 15973: Comparison Between Unipolar and Bipolar Radiofrequency Lesions Using an Irrigated Multi-Electrode Circular Ablation Catheter in the Canine Thigh Muscle Preparation: Effects of Electrode Contract on Lesion Size
Introduction: A circular radiofrequency (RF) ablation catheter with 10 irrigated (IRG) electrodes has been developed for pulmonary vein isolation (nMARQ, Biosense Webster, Inc). Each 3 mm electrode has 10 IRG holes, with 4 mm spacing (Fig ). The purpose of this study was to compare lesion size between unipolar (UNI) and bipolar (BIP) RF applications, with and without one of two electrodes (E) in contact (Fig) , in a canine thigh muscle preparation.
Methods: In 4 dogs (20-26 kg), the skin over the thigh muscle was incised and raised to form a cradle which was superfused with heparinized blood (ACT >350 sec) at 37 °C. Two adjacent E were positioned against the muscle in 2 modes: 1) both E in contact at 10 gram force; and 2) one E in contact (10 g) with one E lifted 1 mm from the surface (Fig ). RF was delivered simultaneously to each of the two E in UNI mode (25 W for 60 sec, max E temperature 47 °C, IRG 6 ml/min per E) at 12 sites with both E in contact and 12 sites with one E in contact, and in BIP Mode (15 W between the two E for 60 sec, max E temp 47 °C, IRG 6 ml/min per E) at 12 sites with both E in contact and 12 sites with one E in contact. These power and E temp limits were found to prevent thrombus in earlier thigh muscle studies.
Results: During UNI RF with E in contact, E temp reached 47 °C in all but 2 RFs limiting UNI power to median 16.7 W. In E without contact, UNI power was not limited by E temp (full 25W). BIP RF reached 47 °C at 3/12 sites with both E in contact (median 14.5 W) and reached 47 °C at all 12 sites with one E in contact (11.3 W). All UNI and BIP lesions with both E in contact were continuous, but lesion size was significantly greater for UNI RF (max depth: median 6.0 mm vs 4.3 mm; and length: median 14.7 mm vs 12.2 mm, Fig ). With one E in contact, lesions were shorter in both modes and shallower in UNI mode (Fig ).
Conclusions: With both E in contact, UNI and BIP RF lesions were continuous. UNI lesions were consistently deeper and longer. Loss of contact with one E limits both length and depth, and may prevent continuous transmural lesions.
- © 2013 by American Heart Association, Inc.