Analysis of the vein wall destruction under endovenous laser ablation in an ex vivo model

ABSTRACT This work was aimed at elaborating an experimental ex vivo endovenous laser ablation (EVLA) model and evaluating the possibility of using differential scanning calorimetry (DSC) to determine the degree of collagen denaturation of the venous tissue and optimize the laser treatment settings. The control (non-varicose) and varicose vein specimens were subjected to chemical, thermal and morphological analyses. Varicose vein fragments were irradiated with 1.56-μm and 0.97-μm lasers in conditions closely similar to those of the clinical EVLA procedure. The laser treated specimens were subjected to thermal and histological analyses. A noticeable difference in chemical composition and structure was detected between the control and varicose veins. Glycosaminoglycan content increased significantly in varicose vein (P = .02), elastin content decreased insignificantly (P = .26) while collagen content showed a slight, but not significant, increase (P = .14). Varicose vein demonstrated regional variability in wall thickness, some decrease in the amount of smooth muscle cells, thinning and loosening of collagen fibers and fibrosis. The critical laser radiation power was demonstrated simultaneously to cause complete denaturation of collagen (as indicated by the DSC data) and coagulation necrosis of all the three venous wall layers, total homogenization of the tissue and obliteration of vasa vasorum (as indicated by the histological analysis data). Lower laser radiation powers fail to produce these effects. Critical laser power provides the desired result of the thermal effect on the vein ex vivo, namely, tissue necrosis and vasa vasorum destruction. The complete degradation of the collagen recorded by DSC could be a marker of the irreversible destruction of the vein wall in modeling of endoluminal thermal treatment.