Preliminary investigation into the use of “micro-EVLA” endovenous surgery for bulging aesthetic veins using a 1940nm diode laser and 272-micron bare fibre in a porcine liver model

Aims:Prominent or bulging veins on the temple or around the eyes are usually treated with extra-corporeal laser. However, when too big for laser to be effective, other techniques need to be used. The aim of this study was to evaluate the potential of using an endovenous approach to treat these small veins – a technique that we call “micro-EVLA” (micro-endovenous laser ablation). Methods: We decided to use a 272µm bare laser fibre which we could pass through a 21G “green” hypodermic needle. In addition, we used a 1940nm diode laser, as we have previously shown that the increased affinity of water to this wavelength results in a reduced thermal spread in biological tissues at low powers. We performed 2 sequential studies. The first measured the thermal spread in the porcine liver model using 1W, 2W and 3W, with a pull-back rate of either 5 sec/cm or 10 sec/cm. Two blinded observers measured the total width of the ablation tract, and the spread of tissue ablation from the edge of the fibre. The second assessed the temperature of the liver surface using an infrared camera, above the laser fibre during treatment, with and without cold air cooling.Results: Increased power resulted in significantly increased thermal spread, as did the slower pull-back compared to the faster. We found that 2W at 5 sec/cm (LEED 10 J/cm) appeared to give the optimal ablation with 0.20mm (SD: 0.073) thermal spread from the edge of the fibre. When these settings were used with the fibre positioned 1.0-2.0mm under the surface of the liver, cold air stopped any significant heating of the overlying liver surface.Conclusion: Our micro-EVLA technique produced a controlled ablation tract which appears to avoid the risk of skin burns. Clinical studies are required to confirm this conclusion.