title: Heat conduction from the exceedingly hot fiber tip contributes to the endovenous laser ablation of varicose veins.
abstract: Lower-extremity venous insufficiency is a common condition, associated with considerable health care costs. Endovenous laser ablation is increasingly used as therapy, but its mechanism of action is insufficiently understood. Here, direct absorption of the laser light, collapsing steam bubbles and direct fiber-wall contact have all been mentioned as contributing mechanisms. Because fiber tips have reported temperatures of 800-1,300 degrees C during endovenous laser ablation, we sought to assess whether heat conduction from the hot tip could cause irreversible thermal injury to the venous wall. We approximated the hot fiber tip as a sphere with diameter equal to the fiber diameter, having a steady state temperature of 800 degrees C or 1,000 degrees C. We computed venous wall temperatures due to heat conduction from this hot sphere, varying the pullback velocity of the fiber and the diameter of the vein. Venous wall temperatures corresponding to irreversible injury resulted for a 3 mm diameter vein and pullback velocities <3 mm/s but not for 5 mm and > or =1 mm/s. The highest wall temperature corresponded to the position on the wall closest to the fiber tip, hence it moves longitudinally in parallel with the moving fiber tip. We concluded that heat conduction from the hot fiber tip is a contributing mechanism in endovenous laser ablation.
authors.affiliation: Department of Dermatology, Erasmus Medical Centre, P.O. BOX 2040, 3000 CA, Rotterdam, The Netherlands.
authors.forename: Renate R
authors.initials: RR
authors.lastname: van den Bos
authors.forename: Michael A
authors.initials: MA
authors.lastname: Kockaert
authors.forename: H A
authors.initials: HA
authors.lastname: Martino Neumann
authors.forename: Rolf H
authors.initials: RH
authors.lastname: Bremmer
authors.forename: Tamar
authors.initials: T
authors.lastname: Nijsten
authors.forename: Martin J C
authors.initials: MJ
authors.lastname: van Gemert
mesh_terms: D016342:Angioplasty, Laser / Q000009:adverse effects / Q000295:instrumentation*; D002056:Burns / Q000209:etiology*; D004730:Endothelium, Vascular / Q000293:injuries*; D006801:Humans; D007834:Lasers / Q000009:adverse effects*; D008955:Models, Cardiovascular; D018570:Risk Assessment; D013814:Thermal Conductivity; D013997:Time Factors; D014648:Varicose Veins / Q000601:surgery*