© 2002 by European Society of Cardiology
ELECTROPHYSIOLOGY
Catheter ablation using very high frequency current: effects on the atrioventricular junction and ventricular myocardium in sheep
Division of Cardiology, Hôpital Nord, University of Marseille, School of Medicine Marseille, France; Hôpital Central and Laboratoire d'Instrumentation Electronique Nancy, France
Manuscript submitted 6 September 2000. Accepted after revision 11 October 2001.
Correspondence: Paul Bru, MD, Department of Cardiology, Hôpital Saint Louis, 17019 La Rochelle-France.
Key Words: Catheter ablation, atrioventricular junctional ablaiton, atrioventricular block, radiofrequency, microwave
Background
Radiofrequency ablation is currently used in the treatment of various cardiac arrhythmias. However, this technique is limited by impedance rise, leading to coagulum formation and desiccation of tissue. We developed a new generator, providing very high frequency (27 MHz) current, which is in the intermediate range between radiofrequency and microwave energy. The aim of this study was to evaluate the results for catheter ablation of the atrioventricular junction and characteristics of the lesions obtained at ventricular sites.
Methods and Results
The generator was coupled to a specially designed 7-French coaxial catheter. The study included experiments performed on 10 sheep (Wt. 31–42 kg). In seven sheep, the catheter was introduced into the femoral vein and advanced across the tricuspid annulus to record the largest possible His electrogram. VHF current was applied for 25 s, with increasing energies. The energy needed to obtain complete atrioventricular (AV) block ranged from 60 to 100 Watts. Six animals were observed for 6 to 21 days. Complete AV block was found to be persistent. In those seven sheep in whom AV junction was ablated and in three additional sheep, the ablation catheter was positioned toward the right ventricular apex using the same approach and into the left ventricle via the femoral artery, and 20 to 90 Watts energy was delivered in order to assess the size of the induced lesions. Side effects included ventricular tachycardia degenerating into ventricular fibrillation in six cases, but the same effect was observed in this animal model with radiofrequency energy. No cardiac perforation was noted. No thrombus was observed at the catheter tip. The size of the lesion ranged from 3 to 45 mm in width and 1 to 15 mm in depth.
Conclusions
Catheter ablation using VHF current is feasible and appears effective in producing stable AV block when applied at the AV junction and results in substantial myocardial lesions. Further studies are needed to define its clinical interest and side effects.
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