Development of a new intraoperative radiofrequency ablation technique using a needle electrode

We studied a new intraoperative technique for radiofrequency ablation using a needle electrode. The ventricles of 12 mongrel dogs were ablated. The needle electrode was inserted to a depth of 3 mm through the epicardium. Macroscopically, tissue defect was found only at the needle insertion site. The degenerated area had a well-demarcated bullet shape with microscopical coagulation necrosis. This characteristic shape allows the ablation of deeper areas of the myocardium by deeper insertion of the ablation needle. Compared with conventional epicardial surface ablation, this new method could be used to achieve deeper coagulation. For any given energy level and conductance, the ratio between the volume and the depth of the lesion with this new method is smaller than that of lesions made by the conventional radiofrequency ablation method. With this new method, the energy spreads vertically, a characteristic suitable for deep ablation. This may result from the shape of the needle electrode itself. For ablation of deep targets, this new method is superior to the conventional approach because less myocardium is coagulated and the target can be ablated with greater efficiency, requiring the destruction of less tissue. In conclusion, the needle electrode procedure can achieve a narrower ablation for deeper targets than can the conventional technique.