Bimodal electric tissue ablation: Positive electrode studies

Background: Bimodal electric tissue ablation is a novel variation to standard radiofrequency ablation that produces significantly larger ablations by the addition of a direct electrical current. The negative electrode is attached to the radiofrequency current and the positive electrode is placed nearby. It has been identified that an electrolytic injury can occur at the positive electrode site. It is suggested that by increasing the surface area that is in contact with the positive electrode, the risk of tissue injury is reduced. This hypothesis was tested in a pig model. Methods: Thirty-six ablations were carried out in the livers of six pigs (six ablations per pig). Two were standard radiofrequency ablation controls and two were carried out with positive electrode attached to a scalpel blade. Two were carried out with positive electrode attached to a grounding pad. After 48 h, liver was harvested and the ablation sizes were compared. Skin biopsies were taken from the scalpel site and one from the pad site and examined histopathologically. Results: The scalpel blade ablations were significantly larger than controls and the grounding pad ablations (P < 0.001). The grounding pad ablation was significantly larger than controls. The scalpel blade skin site showed full-thickness tissue injury. The grounding pad site appeared microscopically normal. Conclusion: By increasing the surface area that connects to the positive electrode, significantly larger ablations can be carried out while minimizing the risk of associated tissue injury.