Objective. The aim of the study was to compare the laser radiation effects on venous walls in the continuous and in the pulsed regimes in an experiment.

Materials and methods. A Nd-YAP 1.4 mm laser was used to generate laser radiation in a pulsed mode and a diode 1.5 mm laser was used to generate the laser radiation continuous mode. A linear endovenous energy density (LEED) of radiation from 30 to 75 J / cm was used. The great saphenous vein washed from the blood and immersed in physiological saline was exposed to radiation. The bar tip fiber was used. The results were evaluated macroscopically (color change, degree of constriction, presence of carbonizations and perforations) and microscopically. For the microscopic evaluation, the preparations were stained with hemothoxylinosein and trichrome (MSB).

Results. Nine veins samples were evaluated macroscopically and microscopically for each regime. Almost all the preparations exposed to 30—50 J / cm of LEED had changes characteristic for thermal injury. With the same LEED of radiation, the changes intensity was larger with the pulsed radiation.

Conclusion. 1. The effectiveness of endovenous laser ablation (EVLA) is influenced not only by the radiation power and wavelength but by the laser radiation generation mode (pulsed or continuous) as well. 2. To achieve vein coagulation in EVLA using laser radiation generated in the pulsed mode, less energy is required than when using laser radiation generated in a continuous mode.