Reply to letter to the editor re: Investigation on radiofrequency and laser (980 nm) effects after endoluminal treatment of saphenous vein insufficiency in an ex-vivo model.

We would like to thank Serge Mordon and his group for their stimulus to an important discussion, which was one of the aims of our paper to initiate. Our first series of experiments indicate that ELT leads to a wide variation in the effects on tissue within a certain treatment protocol. This may be due to a very complex mechanism of endovenous laser-induced thermal alteration. In ELT, energy level does not seem to be the single variable influencing thermal effects on endovenous tissue. Mordon et al. presented an interesting mathematical model for evaluation and demonstration of tissue heating during ELT. There findings confirm our own theoretical calculations. Human saphenous veins are, as a rule, completely surrounded by fatty tissue.This condition can be assumed and is adequately represented by our model. In addition, to our knowledge, heat conductivity of muscle tissue is only slightly higher than that of fatty tissue (fatty tissue: 0,1-0,37 W/(m K), muscle tissue: 0,34-0,68 W/(m K)). Experiments in our ex-vivo model were performed without tumescent anesthesia. We assume that heat conductivity of tumescent fluid (normal saline with highly diluted local anesthetic) is similar to tissue with around 0,5 W/(m K). We do not think that perivascular tumescence directly influences the intravenous thermal effects of ELT such as uniform distribution of heat inside the vessel, as proposed by Mordon et al. Tumescence may reduce vein-lumen diameter due to perivascular pressure and it enlarges the distance between treated vein and perivenous fatty tissue, nerves and skin thus avoiding thermal injury of these structures. In conclusion, we think that our ex-vivo cow’s foot model adequately represents the clinical situation for