Thermal damage of the inner vein wall during endovenous laser treatment: key role of energy absorption by intravascular blood.

BACKGROUND: Despite the clinical efficacy of endovenous laser treatment (EVLT), its mode of action is incompletely understood.

OBJECTIVE: To evaluate the role of intravascular blood for the effective transfer of thermal damage to the vein wall through absorption of laser energy.

METHODS: Laser energy (15 J/pulse, 940 nm) was endovenously administered to explanted greater saphenous vein (GSV) segments filled with blood (n = 5) or normal saline (n = 5) in addition to GSVs under in vivo conditions immediately prior to stripping. Histopathology was performed on serial sections to examine specific patterns of damage. Furthermore, in vitro generation of steam bubbles by different diode lasers (810, 940, and 980 nm) was examined in saline, plasma, and hemolytic blood.

RESULTS: In saline-filled veins, EVLT-induced vessel wall injury was confined to the site of direct laser impact. In contrast, blood-filled veins exhibited thermal damage in more remote areas including the vein wall opposite to the laser impact. Steam bubbles were generated in hemolytic blood by all three lasers, while no bubbles could be produced in normal saline or plasma.

CONCLUSION: Intravascular blood plays a key role for homogeneously distributed thermal damage of the inner vein wall during EVLT.