Evaluation of Setpoint Temperature and Pullback Speed on Vein Adventitial Temperature During Endovenous Radiofrequency Energy Delivery in an In-Vitro Model

Abstract

Endovenous occlusion of the greater saphenous vein with radiofrequency (RF) energy has been shown to be a safe and effective treatment for saphenofemoral reflux. Operating parameters initially developed for the VNUS ®Closure ®system were selected in order to provide sufficient energy to controllably and transmurally heat the vein wall to cause collagen contraction and destruction of the vein wall while limiting the degree of perivascular heating. Procedural advances, such as ultrasound-guided tumescent infiltration along the course of the vein to be treated, have provided an added level of thermal protection to the perivenous tissue during the application of RF energy. The purpose of this study was to evaluate the effect of raising the setpoint temperature from 85°C to 90°C while doubling the pullback speed from 3 to 6 cm/minute on vein adventitial temperature. An in vitro simulation of a peripheral vein surrounded by body tissue was created by fixing freshly excised bovine veins in beefsteak kept moist by normal saline. A VNUS RF generator, in conjunction with a VNUS Closure catheter, delivered temperature-controlled RF energy to the bovine vein intima. Adventitial temperatures were recorded as the catheter was withdrawn and peak temperatures from 4 treatment groups were analyzed. The mean peak adventitial temperatures for the groups in which the adventitia was lightly bathed in saline were 64.4°C and 64.9°C with a setpoint temperature of 85°C at a pullback speed of 3 cm/minute and 90°C at a pullback speed of 6 cm/minute, respectively. The mean peak adventitial temperatures for the groups in which the adventitia was bathed in a 2.0 mm layer of saline were 51.3°C and 47.7°C with a setpoint temperature of 85°C at a pullback speed of 3 cm/minute and 90°C at a pullback speed of 6 cm/minute, respectively. Temperature-controlled radiofrequency occlusion of the saphenous vein, performed using an intimal setpoint temperature of 90°C and double the pullback speed of the historical VNUS Closure treatment (6 vs 3 cm/minute), produced comparable temperatures at the adventitial surface in an in vitro model. The addition of a 2.0 mm layer of saline significantly reduced the peak adventitial temperatures.

Get full access to this article

View all access options for this article.

References

Weiss RA : Comparison of endovenous radiofrequency versus 810 nm laser occlusion of large veins in an animal model. Dermatol Surg 28:56-61, 2002.

Goldman MP , Weiss RA , Bergan JJ : Varicose veins and telangiectasias. Circulation 12:219-223, 1999.

Weiss RA , Weiss MA : Controlled radiofrequency endovenous occlusion using a unique radiofrequency catheter under duplex guidance to eliminate saphenous varicose vein reflux: A 2-year follow-up. Dermatol Surg 28:38-42, 2002.

Merchant RF , DePalma RG , Kabnick LS : Endovascular obliteration of saphenous reflux: A multicenter study. J Vasc Surg 35:1190-1156, 2002.

Kabnick LS , Merchant RF : Twelve and twenty-four month follow-up after endovascular obliteration of saphenous vein reflux. J Phlebol 1:17-24, 2001.

Hayashi K , Thabit G , Massa KL , et al: The effect of thermal heating on the length and histologic properties of the glenohumeral joint capsule. Am J Sports Med 25:107-112, 1997.

Morrison N , Neuhardt D : Radiofrequency Closure treatment of greater saphenous vein reflux utilizing increased heat and increased pullback rate. Poster presented at: 16th Annual Congress of the American College of Phlebology; November 7–10, 2002; Fort Lauderdale, FL.

Proebstle TM , Lehr HA , Kargl A , et al: Endovenous treatment of the greater saphenous vein with a 940-nm diode laser: Thrombotic occlusion after endoluminal thermal damage by laser-generated steam bubbles. J Vasc Surg 35:729-735, 2002.

Proebstle TM , Sandhofer M , Kargl A , et al: Thermal damage of the inner vein wall during endovenous laser treatment: Key role of energy absorption by intravascular blood. Dermatol Surg 28:596-600, 2002.

10.

Porto LC , da Silveira PR , de Carvalho JJ , et al: Connective tissue accumulation in the muscle layer in normal and varicose saphenous veins. Angiology 46: 243-249, 1995.