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Introduction
The unique characteristics of the superficial femoral artery present challenges for revascularization. To safely and effectively treat this difficult multivariate disease state, a versatile treatment option is necessary. For a percutaneous device to be successful, it needs to be strong and flexible enough to withstand the anatomical forces without losing structural integrity.

Nitinol stents in the superficial femoral artery (SFA) have fared better than stainless steel self-expanding stents and balloon-expandable stents. The 1-year patency rates of nitinol stents are approximately 60–70% versus 50–60% for stainless steel self-expanding and balloon-expandable stents.¹ Percutaneous treatment of SFA lesions usually requires either contralateral femoral or ipsilateral common femoral antegrade access. In cases with flush SFA occlusions due to an inability to find the true ostium of the SFA, these approaches are not useful. Alternatives in this instance include referral to surgery for an open bypass procedure, a hybrid procedure like a remote endartectomy or an attempt via the popliteal approach. In this case report, recanalization of an SFA chronic total occlusion (CTO) via the popliteal approach with use of a self-expanding nitinol stent graft (Viabahn, WL Gore & Associates, Flagstaff, Arizona) is described.

Case Report
A 74-year-old patient presented with activity-limiting claudication of the left leg. He was initially treated conservatively and underwent non-invasive duplex imaging and ankle-brachial index (ABI) estimation. This documented an ABI of 0.5. Doppler imaging confirmed the presence of a long SFA occlusion. He was free of activity-limiting claudication for 1 year on medical therapy. At 15-months follow-up, he reported significant worsening of symptoms and interference with his lifestyle.

The patient underwent angiography via the femoral approach. This confirmed the findings of non-invasive imaging. A long SFA occlusion (TASC D) with recanalization at the adductor canal, two vessel run-off to the left foot via the anterior tibial and peroneal artery and patent plantar arch vessels were noted on angiography. He was advised of the alternative treatments, including a discussion about remote endartectomy, open bypass and a percutaneous attempt via the popliteal approach. In the prone position, popliteal access was obtained. An 8 Fr sheath was placed in the popliteal artery. A super stiff Terumo Glide Wire (Terumo Medical Corporation, Somerset, New Jersey) was used to probe the occlusion with and without backup catheter support. It was not successful in crossing the occlusion. A Frontrunner catheter (Cordis Endovascular Inc, Redwood City, California) was then used to cross the occlusion. Once the CTO was traversed, the Frontrunner catheter was replaced with a super stiff Terumo Glide Wire. With the wire in the iliac artery, angioplasty was performed with a 6-mm Fox (Jomed Inc., Rancho Cordova, California) balloon and then a Viabahn stent graft was advanced through the occlusion to the proximal SFA. Care was taken to deploy the graft proximal to the origin of the SFA bifurcation to preserve the ostium of the profunda femoral artery. Post dilatation of the graft was carried out at high inflation pressures and care was taken to ensure at least a 1.5 mm overlap between the two stent grafts used. A Perclose (Abbott Vascular Inc., Redwood City, California) was used to close the arterotomy site, and the patient was discharged the next day. At 30-day follow-up, the patient had marked improvement in his functional class and his ABI improved to 0.8.

Discussion
Major infrainguinal occlusions can occur with minimal symptoms due to the potential for collateralization and the frequent accompanying coronary atherosclerosis, limiting the patient’s activity level. Conservative treatment for functional class I is usually justified because the natural history of femoro-popliteal disease suggests slow progression of symptoms from stage 1 to more advanced stages.² The optimal treatment strategy for long SFA lesions in symptomatic patients remains controversial.

The time-tested surgical approach involves using a either an autologous saphenous vein or a prosthetic PTFE (polytetrafluoroethylene) graft to bypass the long SFA occlusions. The 4-year patency rates of either of these grafts for above the knee femoro-popliteal bypasses are in the 50–60% range.³ The outcome, as far as patency, is identical with in situ versus reversed saphenous vein grafts in femoro-popliteal bypass conduits.⁴ Intimal hyperplasia, progression of disease (proximally or distally) or lesions in the graft itself can produce signs of hemodynamic deterioration without thrombosis in the graft. This entity is called the “failing graft,” and without some intervention, graft thrombosis is almost certain to occur.⁵

Alternative treatment involves a remote endartectomy (RSFAE). RSFAE is a minimally invasive procedure performed through a limited groin incision (femoral arteriotomy). RSFAE can be performed with the MollRing Cutter device (Vascular Architects, Inc., San Jose, California). The distal plaque requires “tacking up” with a stent that is flexible and able to withstand compressive forces proximal to the knee joint. In one trial, the primary assisted patency rate was 88.5% ± 8.5% at 18 months in this difficult lesion subset.⁶ If results of this type can be duplicated in larger randomized trials, then RSFAE may become an important hybrid therapy available to these patients. However, the lesions addressed were not total occlusions.

Femoro-popliteal percutaneous translumial angioplasty (PTA) serves as niche therapy for focal lesions less than 5 cm in length. The primary patencies at 12 years for lesions that are < 5 cm are 58% and 51%, respectively.⁶ Short, focal lesions do not compromise the vast majority of lesions that require revascularization. Another new, minimally invasive technique is subintimal angioplasty. This is a technique with a niche role in patients with chronic limb ischemia with lesion characteristics in whom PTA alone is known to be a poor option. These include long occlusions (> 15 cm), highly calcified lesions, diffuse tandem lesions and flush occlusions. Subintimal angioplasty studies have suggested a technical success rate of 74–81% and 1-year patency rate of 55–74%.⁷ A variation of this concept is called the subintimal arterial flossing with antegrade retrograde intervention (SAFARI) technique. With this technique, the technical success has been reported to be 100%, with a 6-month limb salvage rate of 90%.⁸

The advent of low-profile, self-expanding nitinol stents has changed the landscape of endovascular femoro-popliteal disease treatment. Recently noted nitinol stent strut fractures, however, have sounded a sobering word of caution.¹⁰ In the SIROCCO trial, the primary unassisted patency rate of bare nitinol stents at 18-month duplex follow up was 82.9%.¹¹ There are no randomized controlled trials comparing nitinol-based self-expanding stents with PTA or for that matter, atherectomy. The RESILIENT and STRIDES trials will be two such trials, randomizing patients with SFA lesions less than 15 cm in length to PTA or self-expanding nitinol stents.

Another percutaneous option is use of stent grafts. The Viabahn endoprosthesis recently gained approval by the Food and Drug Administration in June of 2005 for treatment of SFA disease. The stent graft consists of a self-expanding helical nitinol stent and a tube of radially enforced, 0.1-mm thick, expanded polytetrafluoroethylene. The pore diameter is 30 um. Most published studies have shown favorable patency rates at 12 months of approximately 50–65%.13 However, Jahnke et al. reported a short (1-year) and a medium (2 years) patency rate of 78.4% ± 5.8 and 74.1% ± 6.2, respectively.¹² A potential drawback of use of stent grafts is the coverage of collaterals, thereby putting the treated limb at risk of limb-threatening ischemia in the event of stent thrombosis. Thigh discomfort has been reported in 6–20% of patients undergoing placement of stent grafts in the SFA.⁹ This symptom may be related to an inflammatory response. Additional symptoms may be a low-grade fever. This usually responds to conservative care and anti-inflammatory or analgesic medications. There have not been any reported cases of covered stent migrations. Endoleaks are not a concern with stent grafts when used to treat peripheral vascular stenoses/occlusions, since the purpose of the device is to create a new vascular channel rather than to exclude an aneurysm. With prosthetic grafts, restenosis occurs in the inflow vessel, outflow vessel or at the anastamotic site of the bypass graft. There are no data on the benefit of surveillance programs for femoral stent grafts or for nitinol stents. Outside of clinical trials, symptom progression or changes in the functional class serve as surrogate markers for graft failure. Most restenosis, however, occurs in the first year after the implant.

Conclusion
This vignette highlights several important aspects in the care of patients with long SFA occlusions. Due to the inevitable presence of dissection planes associated with recanalization of CTOs, atherectomy devices can propagate those dissection planes, and stand-alone angioplasty (cryoablative or otherwise) is insufficient to prevent acute re-occlusion. Hence, the only viable therapy other than a bypass procedure is routine stenting after initial recanalization. There is a dearth of data in the optimal management of patients with long SFA lesions, especially when CTOs are being treated. The presence of flush SFA occlusions should promptly alert the operator of the need to use the popliteal artery as the access site if percutaneous therapy is entertained. Stent graft utilization offers some theoretical advantages over nitinol-based stent technology, due to the demonstration of a slower rate of re-endothelialization in the presence of PTFE. Unfortunately, there has not been any demonstration of superiority in terms of target vessel revascularization in a randomized control setting for stent grafts versus nitinol-based stent technology. This controversy is even more difficult to resolve since there are no studies that focus only on CTOs in the peripheral vasculature. Yet regardless of which stent technology is utilized, oral antiplatelet therapy is still required to optimize long-term patency, as well as risk factor modifications.