Applied Radiology

Percutaneous interventions for varicose veins

Dr. Martinez is a fellow in Vascular and Interventional Radiology at Georgetown University Medical Center, Washington, DC. Dr. Martinez received his MD from Ponce School of Medicine, Puerto Rico, and completed his residency in Diagnostic Radiology at The University of Connecticut Health Center, Farmington, CT.

Chronic venous disease plays a significant role in medical referral in today's world. Incompetence of the saphenofemoral junction (SFJ) with reflux into the greater saphenous vein (GSV) is one cause of chronic venous hypertension, which may lead to the development of varicose and telangiectatic leg veins. For years, surgical ligation and stripping of the GSV has been the gold standard for treatment of SFJ incompetence. This article reviews percutaneous interventional therapy for this condition as an alternative to surgery. Interventional radiologists should be involved directly in the clinical assessment and therapeutic management of symptomatic varicose veins.

Chronic venous disease of the lower limbs ranks as one of the most common conditions affecting humankind. Based on an earlier health survey conducted in the United States, the diagnosis of varicose veins was the seventh most common reason for medical referral. ¹ It is estimated that 3% to 8% of the U.S. population has symptomatic lower extremity venous valvular insufficiency, and 1% of adults older than 60 years of age have chronic ulceration. ² The total cost to the U.S. economy was approximately $1 billion in 2000. ² Although approximately half of the U.S. population has minor stigmata of venous disease (women 50% to 55%; men 40% to 45%), fewer than half of this population will have visible varicose veins (women 20% to 25%; men 10% to 15%). ²

The prefix "varic(o)" means twisted and swollen. ² Varicose veins in the lower extremities can be defined as any prominent vein that has permanently lost its valvular efficiency and, as result of continuous dilatation under pressure, becomes elongated, tortuous, pouched, and thickened (Figure 1). Among the predominant risk factors associated with the development of varicose veins include female gender, increased age, and pregnancy. ²

The venous system of the lower extremity has two components­­the superficial and the deep systems­­separated by a deep fascial layer. Bicuspid valves are present in the venous system and permit flow in only one direction, toward the heart. The number of valves increases from proximal to distal; therefore, proximal valve damage has greater consequences than does isolated damage to distal valves.

The first component of the venous system, the superficial system, collects blood from both the subcutaneous tissues and the skin. This system empties into the deep system and consists of three main branches: 1) the greater saphenous vein (GSV), 2) the lesser saphenous vein, and 3) the lateral venous system.

The first main branch, the GSV, originates as a continuation of the medial venous arch of the foot. This vessel courses upward along the medial aspect of the calf to the level of the knee. At this level, the saphenous nerve is in proximity to the vein, making it susceptible to inadvertent injury during saphenous vein treatment. From the knee, the vessel courses more medially, along the medial aspect of the thigh, to join with the common femoral vein in the groin (Figure 2). The second branch, the lesser saphenous vein, arises along the lateral aspect of the foot as a continuation of the dorsal venous arch. This vessel extends up in the posterior calf toward the knee and joins the popliteal vein (Figure 3). The final branch, the lateral venous system, is a system of small-caliber veins located along the lateral aspect of the leg. These veins drain toward the perforator veins of the knee (Figure 4). The perforating veins are small veins that connect the superficial to the deep venous system (anterior and posterior tibial, peroneal, popliteal, and superficial femoral veins), allowing flow in that direction only (Figure 5). The number of perforators found in the leg varies greatly; some reports suggest more than 15,000 perforators within a leg. In general, these veins are considered in loose regional groups. ³ Four distinct groups of perforator veins associated with the GSV tributaries are the Hunterian's, Dodd's, Boyd's, and Cockett's ⁴ (Figure 6).

Most varicose veins are associated with valvular insufficiency of one of the aforementioned branches of the superficial venous system. A second cause of superficial varicosities is valvular incompetence in the perforator veins, as a result of a high-pressure leak gradient toward the superficial venous system with subsequent dilatation and varicosity formation. Reflux within any of these perforators can result in varicose veins even in the absence of reflux within the saphenous system. ⁴

Clinical assessment

The clinical assessment of chronic venous valvular disease is usually performed using duplex ultrasonography. With duplex ultrasonography, detailed information about the venous anatomy and valvular function can assist the clinical diagnosis of valvular insufficiency. In a venous insufficiency duplex ultrasound, functional abnormalities are evaluated, and the imaging must be performed in a position that maximizes the reflux, such as the standing position. The patient performs Valsalva's maneuver during real-time duplex observation so flow changes can be evaluated and, in some cases, dysfunctional valves identified (Figure 7).

A saphenous vein mapping is also performed. The examination begins at the saphenofemoral junction (SFJ), following the saphenous vein from this point inferiorly to the ankle. The identity of the GSV should be confirmed throughout its course by noting its relationship to the surrounding fascial layers. When the GSV has been mapped in its entirety, the deep venous system should be examined in detail to ensure its patency. If the GSV is the primary venous conduit circumventing an occluded deep venous system, it cannot be sacrificed for any surgical or interventional procedure.

In general, there are four specific objectives of the color-duplex examination of patients with varicose veins that should be addressed: 1) determine whether the deep and superficial venous systems are patent, 2) identify and localize reflux in the deep and superficial venous systems, 3) determine blood flow source to the varicose segments, and 4) evaluate the potential benefits of occluding the source of inflow to the varicose segment. ⁴

Ascending and descending contrast venography are also alternative methods to evaluate the venous system. Although these methods yield anatomic information, they are invasive and do not always provide functional information.

Treatment

Traditionally, surgical ligation or vein stripping has been performed to treat varicose veins and they have been proven to be the most successful treatment methods for truncal varicosities when the SFJ and the GSV are incompetent. ^3,5 These treatments can be very painful and often require prolonged recovery. In addition, this surgical treatment is not free of recurrence. Sarin et al ⁶ reported an 18% rate of recurrence of GSV reflux after ligation and stripping and a 45% rate of recurrence after high ligation alone, appearing as early as 3 months after treatment. Similarly, Dwerryhouse and colleagues ⁷ found a recurrence rate of 29% after ligation and stripping of the GSV and a rate of 71% after high ligation.

Recently, new percutaneous endovenous techniques have been introduced that permit minimally invasive treatment of superficial venous insufficiency.

Endovenous radiofrequency vessel occlusion

In the treatment of varicose veins due to reflux arising from the SFJ into the GSV, the goal is to eliminate saphenofemoral reflux by obliterating a long segment of vein from within the lumen in lieu of ligation and stripping. Although the concept of endovenous elimination of reflux is not new, previous approaches relied on electrocoagulation of blood, causing thrombus to occlude the vein. The potential of recanalization of the thrombus is high through endothelial migration. ^8-14

Endovenous closure of the GSV by contraction of the venous wall produced by thermal heating can be obtained using a radiofrequency device, the Closure catheter (VNUS Medical Technologies, San Jose, CA). Radiofrequency is a form of electrical energy that may cause tissue destruction. Delivered in a continuous or sinusoidal wave mode, radiofrequency produces no stimulation of neuromuscular cells by using a high frequency between 200 to 3000 kHz. The frequency range (460 kHz) for the Closure device (VNUS Radiofrequency Generator, VNUS Medical Technologies) causes excitation of molecules (resistive heating) in a vessel wall with subsequent collagen contraction in the vein wall and thermocoagulation without causing muscle stimulation or other undesirable effects. Bipolar electrodes heat the vein wall, while insulated electrodes collapse when the vein shrinks, allowing maximal physical contraction ¹⁵ (Figure 8). Animal studies have shown endothelial denudation along with denaturing the media and intramural collagen, causing acute vein diameter contraction with a subsequent fibrotic seal of the vein lumen (Figure 9). Deeper tissue planes are then heated by conduction from the small volume of heat. Heat dissipation from the region occurs by further heat conduction into normothermic tissue identification ¹⁵ (Figure 10).

Consistent therapeutic outcomes with the Closure device rely on the attainment and maintenance of a stable target temperature for a specific period of time. The determinants of achieving a stable temperature during the Closure procedure consist of proper electrode-to-vein contact and blood flow through the segment of the vein treated. Inadequate electrode contact of the vessel wall will not allow establishment or maintenance of a target temperature. Flow of blood through the vessel during treatment can prevent proper heating of the vein wall by acting as a "heat sink" (Figure 11). Therefore, monitoring and maintaining good electrode-to-tissue contact (impedance) and restricting blood flow through the segment of vein being treated are important in achieving a consistent therapeutic outcome. ¹⁶

The Closure catheter includes a collapsible electrode, around which the vein shrinks, and a central lumen that allows fluid delivery. Heparinized saline (10 U/mL) is infused through the lumen at a rate of 2 m L/min to inhibit coagulum formation on the electrodes. The control unit displays power, impedance, temperature, and elapsed time so that precise temperature control is achieved. ¹⁵ Veins from 2 to 12 mm in diameter have been successfully closed in the experimental model. ¹⁷

The Closure procedure is performed initially by obtaining anesthesia, injecting a 0.1% lidocaine solution along and around the entire length of the GSV, and performing a small dermatotomy over the distal aspect of the GSV in the distal medial thigh. A 6F or 8F VNUS endoluminal catheter is then inserted approximately to within 1 to 2 cm from the SFJ (Figures 12 through 14). Manual pressure is placed on the groin area, and the VNUS Radiofrequency Generator is activated. After waiting for the vein to reach 85šC for 30 sec, the catheter is pulled back at a rate of approximately 3.5 cm/min. During the pullback, the temperature is maintained between 80š and 90šC, averaging approximately 85šC. During the catheter pullback, the temperature may drop briefly due to the electrodes crossing the ostium of a tributary or perforator vein. When that happens, the pullback speed is slowed to allow the temperature to return to 85šC and occlude the ostium of the tributary or the perforator. At the end of the pullback, the vein is assessed for closure using Duplex ultrasound (Figure 15). The distal varicose tributaries are then subsequently treated with standard ambulatory phlebectomy or sclerotherapy. ¹⁵ The clinical results of the Closure device demonstrate that 90% of treated limbs are reflux-free at 2-year follow-up ¹⁸ and 94% of veins treated were invisible sonographically at 2-year follow-up. ¹⁹ A recent study done by Rautio et al, ²⁰ comparing postprocedural pain, convalescent period, and cost of the Closure device with the conventional stripping operation, revealed that the postoperative average pain, recovery time (6.5 days vs. 15.6 days), and cost of the endovenous obliteration alternative is significantly less than with conventional surgery.

Endovenous laser vessel occlusion

The treatment of truncal varicose veins using an endovenous laser beam is based on the concept of selective photothermolysis. A variety of lasers have been developed recently for the treatment of vascular lesions. By using a wavelength of light well absorbed by the target and a pulse duration short enough to confine thermal injury spatially, specific vascular injury could be produced. Longer wavelengths of light within the visible spectrum penetrate more deeply into the tissue and are more suitable for deeper vessels, whereas longer pulse durations are required for larger caliber vessels. ²¹ Light within a wavelength range of 810 to 980 nm has been used for the different diode laser systems available. A laser beam within this range of wavelength, but more specifically 940 nm, has been shown to be absorbed more easily by water and hemoglobin, and absorbed less easily by melanin than other wavelengths (Figure 16). This allows a high specificity for vessels and a shorter tissue penetration, causing fewer heat-induced side effects, as well as enabling treatment of darker skin types. (Personal communication with spokesperson for Dornier MedTech, Kennesaw, GA, at the SCVIR Annual Meeting, April 2002).

In 1998, the Spanish phlebologist Dr. Carlos Bone, who used a fiberoptic laser fiber endovenously, introduced the alternative of using laser energy for the treatment of incompetence of the SFJ associated with GSV reflux. ²²

The procedure is performed under local anesthesia and ultrasound guidance. Treatment should be limited to GSVs with diameters of 2 to 12 mm (supine position). ²³ Once the sources of venous incompetence and venous mapping of the abnormal pathways are determined, access into the GSV is obtained at the knee level. A 5F introducer sheath (Cook Inc, Bloomington, IN) is inserted over a 0.035-in diameter guidewire. The sheath length ranged from 25 to 45 cm depending on the length of the GSV treated, and the intraluminal position of the tip is positioned approximately 2 to 3 cm from the SFJ. A sterile, bare-tipped 400- to 750-µm diameter laser fiber (Laser Peripherals, Minnetonka, MN) is then inserted into the vein through the sheath with its distal tip positioned approximately 1 to 2 cm below the SFJ. Correct positioning of the laser fiber tip with respect to the SFJ is confirmed sonographically and by direct visualization of the red aiming laser beam through the skin. Manual compression over the SFJ and red aiming beam is applied to achieve maximal vein wall contact with the laser fiber. ^22,23 Diode laser energy (810 nm wavelength by Diomed D15 Diode Laser, Diomed Inc, Andover, MA; and 940 nm wavelength by Dornier MedTech, Kennesaw, GA) is delivered through the fiber along the course of the GSV as the laser fiber is withdrawn slowly at 3- to 5-cm increments ²² (Figure 17). The parameters for the recommended laser energy delivered are 10 to 14 W in continuous mode with laser energy bursts of 1 to 2 sec in duration, for a fluence equivalent to 10 to 28 J, with a single average continuous burst of 15 to 20 J. These parameters produce focal thermal injury to the endothelium and vein wall with extension into the adventitia. ²² After treatment, compression stockings are worn for approximately 7 days. Patients are instructed to continue their normal daily activities without vigorous exercising (Figures 18 and 19). After closure of the GSV, sclerotherapy, ambulatory phlebectomy, or a subsequent intervention using the endovenous laser again is recommended to close remaining branch varicosities (Giacomini, anterolateral branch, etc).

The results of the endovenous laser treatment for GSVs show 99% vessel occlusion at 1 to 9 months follow-up as shown by Min and colleagues, ²³ and a 100% rate of successful occlusion as reported by Navarro et al. ²²

Sclerotherapy

Sclerotherapy as a treatment for GSV incompetence offers another alternative to surgery. By injecting a sclerosant into a vein, irritation of the intima is initiated, followed by an inflammatory reaction in the vein wall. Firm compression is then applied to keep the vein collapsed, thereby allowing granulation tissue and subsequent fibrosis to extend across the lumen of the collapsed vein. This results in a fibrous cord-like vein that is permanently obliterated. ²⁴ Multiple sclerosing agents are available (ethanol, iodine solution, sodium tetradecyl sulfate, sodium salicylate). ²⁵ Some investigators report comparable long-term results to surgery, with success rates of 85% to 90% at 6-year follow-up. ^24­27 Transcatheter duplex ultrasound-guided sclerotherapy is an innovative type of sclerotherapy that uses an endovenous catheter for GSV occlusion. The technical approach is similar to the previously described technique using the laser or radiofrequency systems. On image-guided sclerotherapy, a multisided-hole infusion catheter is placed over a guidewire within the GSV. The catheter tip is located 2 to 3 cm below the SFJ (Figure 20). Emptying the vein should be performed in the Trendelenburg position and by manual occlusion of the SFJ while the sclerosing agent is injected. Vein occlusion is maintained for approximately 2 minutes following catheter removal. Graduated compression stockings (30 to 40 mm Hg) are worn for a minimum of 7 days following treatment. ²⁸ The results of transcatheter duplex ultrasound-guided sclerotherapy showed a persistent vein occlusion at 3 to 12 months follow-up of the patients treated as reported by Min and Navarro. ²⁸

Future therapeutic alternatives

In addition to percutaneous ablation using sclerotherapy or laser or radiofrequency energy, other alternatives of therapy are being researched. The development of a percutaneously placed bioprosthetic bicuspid venous valve is being studied. This approach pursues the re-establishment of the valve mechanism within an incompetent vein. Active investigation is been done by Pavcnik et al, ^29-31 who is using a square stent (Cook Inc, Bloomington, IN) covered with a bioprosthetic material (porcine small intestinal mucosa). A central slit in the bioprosthetic material functions as a one-way hemostatic valve (Figure 21). The intended use of this mechanical valve would be within incompetent veins of the deep venous system in the lower extremities. Use of this device within the GSV is possible potentially, but stent deformation from trauma in a superficial vein can impair the closure valve mechanism. As reported by Pavcnik et al, ^29-31 the use of a square stent covered with porcine small intestinal mucosa in animals has shown positive mechanical and histopathologic results with host cells incorporating the bioprosthetic material into the vein wall as a body's own structure. This, therefore, will prevent the likelihood of failure. A percutaneously implantable, nonimmunogenic venous valve that remains patent and competent over time is an attractive alternative to direct venous valvular reconstruction or transplantation. The potential to treat chronic venous insufficiency and replace natural valves using a covered-square stent is encouraging and warrants further research.

Conclusion

Different therapeutic alternatives are available for the treatment of varicose veins. The introduction of new percutaneous techniques offers a new perspective to the formal treatment of surgery. These techniques have proven to be safe, painless, and more likely to give better results than surgery. The possibility of these procedures being done in an outpatient basis and without anesthesia, in addition to reducing cost and patient satisfaction, will make them the most reliable form of therapy in the treatment of GSV varicosities.