Evaluation of setpoint temperature and pullback speed on vein adventitial temperature during endovenous radiofrequency energy delivery in an in-vitro model.

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 degrees C to 90 degrees 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 Adventitial temperatures were recorded as the catheter was withdrawn and peak temperatures from 4 treatment groups were analyzed.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 degrees C and 64.9 degrees C with a setpoint temperature of 85 degrees C at a pullback speed of 3 cm/minute and 90 degrees 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 degrees C and 47.7 degrees C with a setpoint temperature of 85 degrees C at a pullback speed of 3 cm/minute and 90 degrees 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 degrees 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.