[Radio frequency catheter ablation of the atrioventricular conduction system in a canine model]

Twenty dogs underwent catheter ablation of the AV conduction system with monopolar 300 KHz output to assess the efficacy and the safety of using radio frequency energy at catheter ablation. The energy (15 to 120 W) was delivered between the distal electrode and the back pad until 3 second after complete AV block, which was certified at ECG monitoring. Pathological observation was done with 7 dogs in 2 hours, 6 dogs in 4 to 7 weeks and compared with 10 dogs which underwent catheter ablation with DC energy. Complete AV block was achieved in 15 dogs and there was no return of AV conduction during observed period. The QRS complex of the escape rhythm was similar to those found in sinus rhythm in all dogs. Complete AV block was achieved only when the catheter was located where the H-V interval was longer than 26 msec at the His bundle electrogram before ablation. The damaged area was limited near His bundle and well delineated. AV node was intact in all dogs. Electron micrograph of the damaged areas in acute phase showed the swelling of mitochondria without broken cytoskeletal filaments, which indicate there were no mechanical shocks. There was no patchy fibrosis seen in chronic phase. I conclude that the catheter ablation of the AV conduction system with radio frequency energy is effective and safe, and the minimal damage of the tissue suggests the benefit and the possibility of clinical use.