Cath Lab Digest

Introduction
Successful treatment of symptomatic varicose veins requires a balance between treatment of the underlying etiology and achievement of an optimal cosmetic outcome. In the overwhelming majority of cases, saphenous vein reflux is the primary problem. This superficial venous reflux must be addressed, or recurrence of the varicosities can be expected. In many cases, the varicose veins causing symptoms in the distribution of either the greater or lesser saphenous vein (GSV/LSV) do not need to be excised if the incompetent saphenous vein has been successfully ablated. Current minimally invasive strategies designed to eliminate reflux within the saphenous vein include endovenous radiofrequency ablation and endovenous laser ablation. Foam sclerotherapy also holds promise for the treatment of saphenous vein reflux. Remaining varicose veins can be treated later with stab avulsions, transilluminated powered phlebectomy or sclerotherapy.

Minimally Invasive Treatment of Saphenous Vein Reflux
Minimally invasive endovenous radiofrequency and laser procedures require an initial capital investment for equipment. Also, there will be an acquisition of new disposable items that are specific to each procedure. Duplex ultrasound is utilized during the procedure to identify anatomy and assist with infiltration of tumescent anesthesia. Correct identification of the saphenofemoral junction/saphenopopliteal junction (SFJ/SPJ) with duplex ultrasound is essential to appropriately positioning the ablation/laser catheter. These new endovenous techniques require the treating physician to have ultrasound imaging skills and detailed knowledge of venous anatomy.

Radiofrequency Ablation (RFA)
The Closure procedure (VNUS Medical Technologies, Inc., San Jose, California) is a novel, endovascular, computer-feedback-controlled application of bipolar electrothermal energy that ensures transmural heating of the treated vein wall while minimizing thermal spread to neighboring tissues.^1,2 In most cases, the greater or lesser saphenous vein can be accessed in a percutaneous fashion with cut-down reserved for the difficult-to-access vein. This is a catheter-based procedure in which the saphenous vein is ablated from within by resistive heating.^1,2 Bipolar delivery of radiofrequency (RF) energy directly to the vein wall causes resistive heating that results in total loss of vessel wall architecture, disintegration, and carbonization.^3,4 The device provides continuous impedance and vein wall temperature feedback to a computer generator that allows the operator to vary catheter pull-back speed to ensure effective radiofrequency ablation of the vein.^1,2 Numerous studies have demonstrated that the Closure procedure is an effective surrogate for surgical stripping.

The VNUS system has two main components. The catheter is a sterile, single-use disposable device with sheathable electrodes and a thermocouple at the tip. The catheter comes in two sizes, 6 Fr and 8 Fr, and the tip provides continuous temperature feedback to the RF generator.^1,2 Each catheter also has a central lumen that facilitates through-catheter cannulation with a 0.025” guidewire. This feature is handy for the occasional case in which the catheter does not easily pass from the insertion site to the SFJ. The 6 Fr catheter has four fanned electrodes that can expand from 2–8 mm in diameter, and the 8 Fr catheter has six paired electrodes with an expansion range between 4 and 12 mm.^1,2 The electrodes are designed to engage the intima of the vein wall at the range of diameters of each catheter. Once the electrodes engage the intima, controlled resistive heating causes shortening and thickening of the collagen fibrils as the catheter is slowly withdrawn from its insertion site.^1,2 This process ultimately leads to permanent closure of the treated vein.

The second component of the Closure system is the RF generator. This compact unit recognizes each catheter and selects the appropriate algorithm to effect vein closure.^1,2 The generator has a test button that confirms electrode contact with the vein wall. For instance, “test” numbers would be lower than expected (“normal” at the SFJ for the 6 Fr catheter is > 200 ohms, 8 Fr > 150 ohms) if the catheter was in the large-caliber common femoral vein. These numbers might approximate those seen when the electrodes are opened in saline (100–150 ohms for the 6 Fr catheter and 40–70 ohms for the 8 Fr catheter). During actual treatment, ohms will be > 150 with the 6 Fr catheter and above 100 with the 8 Fr catheter. The RF generator maintains the set temperature with as little wattage as is possible, capped at 6 watts.^1,2 If the temperature or impedance exceed limits set within each catheter’s algorithm, the operator is notified with a displayed error message on the generator. If the condition continues, the RF generator will automatically switch off. Common conditions that disrupt the algorithms include poor vein wall contact by catheter electrodes or thrombus/coagulum at the thermocouple tip.^1,2