Transformational features of the vein wall during a long-term period of endovenous laser ablation using 1910 nm laser radiation. Results of in-vivo experiments.

Background: In this paper, results of in-vivo experiments on the animals of endovenous laser ablation (EVLA) using laser radiation with the wavelength 1910 nm are reported. The results of histological studies of the vein segments removed immediately after the procedure and in a long-term period (30 days and 3 months) are presented. Their structural transformation and the obliteration degree of the vein lumen using different values of the linear energy density of laser radiation (LEED=7.5; 15; 20 J/cm) are estimated.

Methods: Edilbay breed of sheep (males) were used as experimental animals. Laser radiation with a wavelength of λ=1910 nm and power of Рrad = 1.5, 3, 4 W was used for EVLA experiments, and speed of fiber traction (v) was 2 mm/s. 8 days after EVLA stitches and an elastic bandage were removed. Animals were observed for 3 months in the vivarium. Animals have duplex ultrasound scanning of coagulation veins under anesthesia, after analysis vein segments were excised for histological examination. As a result, the damage degree to the vein wall tissues (intima, media, adventitia) and peri-venous tissues was revealed.

Results: It is shown that in the long-time period, the intima and partial muscle layer transformed to connective tissue. EVLA using laser radiation with a higher value of LEED led to the growth of connective tissue, oedema of all vein layers and peri-venous tissue. The lumen closure occurred due to clot and the vein wall transformation, a maximum value was 25% using LEED=20 J/cm.

Conclusions: The connective-tissue transformation of the coagulated vein occurs in a long-term period and more pronounced for higher LEED. However, features of vein hemodynamics of animals and differences between the clot formation process of human varicose veins and healthy animal veins lead to incomplete occlusion. These features should be taken into account during extrapolation results of experiments on animals in clinical practice.