Background/aims: We previously developed a multi-step, incremental expansion method (multi-step method) for radio frequency ablation (RFA) in vitro, which prevented increases in pressure and reduced the ablation time as compared with other methods. In this study, we evaluated liver parenchymal pressure and portal endothelium damage during RFA with different devices and protocols in an in vivo porcine model. Method: Nine healthy female pigs were anaesthetized. RFA was performed with two different devices and protocols; one involved the use of a LeVeen needle with a single-step full expansion method or a multi-step method, and the other used a cool-tip needle with 40 or 60 W power. We measured the pressure in the liver parenchyma and the gallbladder during RFA. We also evaluated portal endothelium damage by NADH staining. Results: The multi-step method with the LeVeen electrode resulted in the lowest parenchymal and intra-gallbladder pressures (multi-step method < single-step method < cool-tip 40 W < cool-tip 60 W). In contrast, the ablation time was shortest with the cool-tip needle at 60 W (cool-tip 60 W <cool-tip 40 W = multi-step method <single-step method). NADH staining revealed severe endothelium damage after ablation with the cool-tip needle, but only slight damage with the LeVeen needle. Conclusion: Ablation with the LeVeen needle, especially when used with a multi-step protocol, produced less of an increase in liver parenchymal and intra-gallbladder pressures and less damage to portal endothelial cells than did the cool-tip electrode.
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