Background Linear Endovenous Energy Density (LEED) is the energy used per cm of vein in endovenous thermal ablation (EVTA) but does not include time. This study examines the effect of time during EVTA. Method EVTA was performed in a previously validated porcine liver model. LEEDs of 40, 60, 80 and 100 J/cm, using different powers were repeated 5 times each. Thermal spread, tissue carbonisation and device-tissue sticking during treatment were recorded. Result LEED positively correlated to thermal spread and carbonisation of the tissue. Power was correlated with carbonisation but not thermal spread. Pullback had no correlations with thermal spread or carbonisation. Catheter sticking found occurred in powers >= 15 W or LEED >= 80 J/cm. Conclusion LEED is a good measure of EVTA but does not include time. Power, which does include time, correlates with carbonisation and with device-tissue sticking. The power used must be quoted with the LEED.

Introduction: Endovenous thermal ablation (EVTA) is the first line treatment of symptomatic truncal venous reflux. Linear Endovenous Energy Density (LEED) is the measure of energy used per cm of treated vein. The rate of application of energy influences thermal spread and tissue damage. However, time is absent from LEED. The aim of this study was to test the effect of time during EVTA in a validated in-vitro model.Methods: We used a bipolar radofrequency catheter and the previously validated porcine liver model to assess any thermal effects. We used combinations of power and pullback speeds giving LEEDs of 40, 60, 80 and 100 J/cm. High-resolution digital images of the ablation tracts were taken. Each setting was repeated 5 times. Thermal spread was measured using digital measuring software, tissue carbonisation assessed by a defined scale and any device-tissue sticking during treatment was recorded.Results: LEED was significantly positively correlated to thermal spread (r(20) = .86, P < .00001) and carbonisation of the tissue (r(24) = .82, p < .00001). Power was significantly correlated with carbonisation (r(24) = .50, p = .009) but not with thermal spread (r(20) = .34, p = .121). Pullback had no significant correlations with thermal spread or carbonisation. Catheter sticking was only found when the power was >= 15 W or the LEED was >= 80 J/cm.Conclusion: LEED is a good measure of EVTA but does not take into account the time of energy application to tissue. Power, which does include time, has a significant correlation with tissue carbonisation, and is also important in device-tissue sticking. Pullback has no significant correlation to any tissue effects. Quoting the LEED alone in reporting EVTA is inadequate. It is essential to include the power used when LEED is quoted.

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