Endovenous laser ablation: a review of mechanisms of action

The aim of this article is to summarize and review the proposed theories on the laser action during endovenous ablation.

Laser mechanics and laser-tissue interaction are summarized from articles found in literature. Several theories, like the "steam bubble theory," the "direct contact theory," the "heat pipe," and "direct light energy absorption" are discussed.

The laser light emitted intraluminally can be absorbed, scattered, or reflected. Reflection is negligible in the near-infrared spectrum. By combining absorption and scattering, the optical extinction of different wavelengths related to different biological tissues can be determined. The direct contact of the fiber tip and the vein wall may be a way of destroying the vein wall, but results in ulcerations and perforations of the vein wall. Avoiding this contact, and allowing direct light absorption into the vein wall, results in a more homogenous vein wall destruction. If the energy is mainly absorbed by the intraluminal blood, the laser fiber will act as a heat pipe. Histological studies show that a more circumferential vein wall destruction can be obtained when the vein is emptied of its intraluminal blood. The use of tumescent liquid reinforces spasm of the vein and protects the perivenous tissue.

Several factors play an important role in the mechanism of endovenous laser ablation. Direct energy absorption by the vein wall is the most efficient mechanism. It is important to empty the vein of its intraluminal blood and to inject tumescent liquid around the vein.