Minimal vascular flows cause strong heat sink effects in hepatic radiofrequency ablation ex vivo.

Abstract

The present paper aims to assess the lower threshold of vascular flow rate on the heat sink effect in bipolar radiofrequency ablation (RFA) ex vivo. Glass tubes (vessels) of 3.4mm inner diameter were introduced in parallel to bipolar RFA applicators into porcine liver ex vivo. Vessels were perfused with flow rates of 0 to 1,500ml/min. RFA (30W power, 15kJ energy input) was carried out at room temperature and 37°C. Heat sink effects were assessed in RFA cross sections by the decrease in ablation radius, area and by a high-resolution sector planimetry. Flow rates of 1ml/min already caused a significant cooling effect (P≤0.001). The heat sink effect reached a maximum at 10ml/min (18.4mm/s) and remained stable for flow rates up to 1,500ml/min. Minimal vascular flows of ≥1ml/min cause a significant heat sink effect in hepatic RFA ex vivo. A lower limit for volumetric flow rate was not found. The maximum of the heat sink effect was reached at a flow rate of 10ml/min and remained stable for flow rates up to 1,500ml/min. Hepatic inflow occlusion should be considered in RFA close to hepatic vessels.