Induction of complete A V block in dogs by transcatheter ablation using high-frequency current: An alternative to direct-current high energy shock

The utility of high-frequency current applied through the distal electrode of a conventional electrode-catheter for altering atrio-ventricular conduction was studied in 18 anaesthetized dogs. Following adequate unipolar His bundle recording, current was applied over periods of 20-30 s, with an output power of 30 W. Complete AV block was achieved in all dogs (four dogs on the third attempt, five on the second, and nine on the first). Ten of the dogs were killed after four hours of continuous ECG monitoring (Group I); examination revealed circumscribed spheroidal myocardial lesions at the base of the right atrium over the posterior tricuspid valve; no thrombus formation was encountered. The remaining eight dogs (Group II) were kept alive for three months during which complete block persisted in all cases. The histologic study showed partial replacement of AV nodal and His bundle tissues and myocardium by fibrous tissue. In conclusion, electro-catheter ablation using high-frequency energy is effective for producing complete AV block. The resulting lesions are circumscribed. This method may prove to be an alternative to the transcatheter DC shock for ablation of the AV conduction system.