Pattern of thermal damage and tissue carbonisation from endovenous radiofrequency ablation catheter – Using an in vitro porcine liver model

Abstract

Background Successful endovenous thermoablation relies on transmural vein wall ablation. We investigated the pattern of thermal spread and tissue carbonisation from RadioFrequency-induced ThermoTherapy (RFiTT) at different powers and pull back methods, using a porcine liver model. Methods We used a previously validated in-vitro porcine liver model. Different powers from 5–25 W were used to administer 150 J. We compared continuous and pulsed energy delivery. Length, lateral spread, and total area of thermal damage, together with any tissue carbonisation, was measured using digital analysis software. Results All experiments used 150 J total energy. Total thermal damage area was smaller with lower power and pulsed energy. Continuous energy caused more tissue carbonisation than pulsed except at 25 W. Conclusion Reduced thermal damage with lower power or pulsed energy results from cooling due to increased time of treatment. Increasing the power increases tissue carbonisation. Optimal treatment is determined by the highest power used continuously that does not cause tissue carbonisation.

Defining the Parameters for Endovenous Microwave Ablation to Achieve Equivalence With Endovenous Laser Ablation, Using the Porcine Liver Model

“…18 However, using this approach, the authors only achieved a 65% occlusion rate at 1 year, although they claimed that 85% had reflux under .5 s. In addition, the use of a live animal model breaks the reduction criteria of the "3 Rs" principle of animal experimentation, when a viable alternative exists. 19 Hence, the porcine liver model, with its ability to measure thermal spread from an EVTA device, has proven very useful in assessing such devices, both RFA and EVLA, 10,13,14 and has been shown to correlate well both histologically with exvivo great saphenous vein 11 as well as with clinical resultsleading to an occlusion rate of 100% at 1 year. 12 However, the aim of this study is not to dictate optimal settings for EMWA, but to use the porcine liver model to show which settings of EMWA produce an equivalent effect as recognised power and pull-back combinations for EVLA.…”

“…Hence, the porcine liver model, with its ability to measure thermal spread from an EVTA device, has proven very useful in assessing such devices, both RFA and EVLA, 10,13,14 and has been shown to correlate well both histologically with ex-vivo great saphenous vein 11 as well as with clinical results - leading to an occlusion rate of 100% at 1 year. 12…”

“…The porcine liver model has been described and validated previously. [10][11][12][13] The previously described protocol for assessment of thermal spread and the blinding of the observers using this model was followed. 14 The fresh porcine liver was acquired from a local butcher and allowed to reach room temperature (21°C) before the experiment commenced.…”

“…The porcine liver model has been described and validated previously. [10][11][12][13] The previously described protocol for assessment of thermal spread and the blinding of the observers using this model was followed. 14 Figure 1 shows the porcine liver model in use.…”

Defining the parameters for endovenous microwave ablation to achieve equivalence with endovenous laser ablation, using the porcine liver model.

“…EVTA requires transmural death of the vein wall for successful long-term ablation by fibrosis. 15,16 The porcine liver model, with its ability to measure thermal spread from an EVTA device, has proven very useful in assessing such devices, both RFA and EVLA, 10,13,14 and has been shown to correlate well both histologically with ex-vivo great saphenous vein 11 as well as with clinical results. 12 As such, we have produced a table of parameters that doctors might refer to when using the ECO EMWA device to attain an equivalent treatment they would achieve with their preferred setting with the Vari-lase 1470nm radial fibre.…”