Transcatheter ablation of the sinus node in dogs using high-frequency current

Sinus node ablation by high-frequency current (HFC) (0.7 MHz. 5-10 W), delivered through the distal electrode of a conventional endocavitary catheter, was induced in seven thoracotomized dogs under autonomic blockade. The HFC was delivered for variable periods of time under ECG monitoring, while sinus tachycardia was produced or after attaining sinus arrest. The procedure was repeated until a stable non-sinus rhythm was obtained. Sinus rhythm was abolished in all seven dogs after a variable number (7-20) of discharges. The escape rhythm obtained after the last discharge, characterized by means of epicardial electrodes and analysis of P-wave morphology, length of PR interval and the rate, showed an atrial activation pattern different from sinus rhythm in all cases. The P-wave was retrograde in two cases, and in one case no atrial activity was detected after the last discharge; however, atrial activity recovered after 35 min, the activation pattern being different from the controls. After 2 h, sinus rhythm had not returned in any case. In no case was there perforation of the atrial wall. Acute histological findings showed coagulation necrosis of the endocardium, extending to the muscle fibres and affecting the sinus cells.