ABSTRACT: Objective. The treatment of long superficial femoral artery (SFA) chronic total occlusions (CTOs) remains controversial. There are several percutaneous treatment options available for the recanalization of these lesions. Percutaneous transluminal angioplasty (PTA) alone, nitinol stents, and expanded PTFE-lined nitinol stents are all viable treatment alternatives to femoral-popliteal bypass surgery. There are, however, limited data on outcomes of patients with SFA CTOs undergoing endovascular treatment. This study was performed to evaluate the safety, efficacy and 1-year patency rates of the Viabahn (WL Gore and Associates, Flagstaff, Arizona) e-polytetrafluoroethylene (e-PTFE) stent grafts at a major medical center in Phoenix, Arizona. Methods. Thirty patients (32 limbs) were prospectively treated for activity-limiting claudication after failing medical therapy. These patients received traditional angioplasty and stenting techniques using the Viabahn e-PTFE stent graft. Follow-up ankle-brachial index (ABI) examinations and duplex surveillance were completed at 6 and 12 months in all patients. Results. The mean age of the patients was 58.4 years. There were 12 women (40%) and 18 men (60%). Five of the patients (16.67%) were diabetics. The procedural success rate was 100%, with no in-hospital morbidity or mortality. The mean preprocedural ABI was 0.54 and the mean SFA occlusion length was 15.4 cm. The mean stented length was 24.6 cm. The median stent diameter was 6 mm. One patient (3.3%) did have subacute stent thrombosis at 4 months. On follow-up testing, the mean post-procedure ABI at 1 year was 0.76 with a primary patency rate of 80% and a primary assisted patency rate of 86%. Silent asymptomatic occlusions were noted in 10% (3/30) of the patients. Restenosis was a prespecified endpoint and was defined as being significant if the proximal peak velocity ratio (PVR) exceeded 2.4 on duplex interrogation. This endpoint was detected in 6.6% of the patient population (2/30) (proximal peak velocity ratio is the ratio of the maximum intrastenotic PSV and the maximum prestenotic PSV). Conclusions. Percutaneous e-PTFE stent-grafting with the Viabahn stent graft is a viable treatment option for TASC D occlusions in the SFA in claudicants and patients with critical limb ischemia. Primary and primary assisted patency rates at 1 year are comparable to historical surgical outcomes using PTFE grafts as bypass conduits. Long-term data (> 5 years) in a larger patient cohort are necessary before definite conclusions can be drawn.
J INVASIVE CARDIOL 2009;21:278–281
Key words: Peripheral vascular disease; endovascular; intervention;
expanded polytetrafluoroethylene (e-PTFE); ankle brachial index (ABI)
Atherosclerotic peripheral vascular disease (PVD) is often an underdiagnosed, undertreated and debilitating disease.1 The 2007 Trans-Atlantic Inter-Society Consensus (TASC) for the Management of Peripheral Arterial Disease document estimates that there are currently 27 million people in Europe and North America who are afflicted with this disease. There are also an estimated 413,000 hospital discharges per year due to chronic PVD.2 The prevalence of PVD increases progressively with age, beginning after the age of 40, a relationship demonstrated by the National Health and Nutrition Examination Survey. The authors found that PVD was present in 0.9% of those between the ages of 40–49 years, 2.5% of those 50–59 years old, 4.7% in the 60–69 year-old group and 14.5% in those ≥ 70 years.3 PVD will thus continue to grow in clinical significance as the world’s population ages.
The use of percutaneous transluminal angioplasty (PTA) to revascularize the superficial femoral artery (SFA) can result in initial technical success rates > 95%, with a low risk of complications.4 However, late clinical failure remains an important concern. Restenosis occurs in 40–60% of treated segments after 1 year. The use of angioplasty to treat extensive disease of the SFA has particularly poor results: at 1 year, the rates of restenosis exceed 70% for lesions longer than 10 cm.5
Stents avoid the problems of early recoil and flow-limiting dissection after balloon angioplasty and can thus be used for the treatment of long and complex lesions. Initial studies of stenting of the SFA reported promising results, with patency rates > 85% at 18 months.6 However, subsequent studies found that exaggerated neointimal hyperplasia frequently leads to in-stent restenosis, and randomized, controlled trials failed to demonstrate any benefit of a stainless-steel stent over angioplasty alone.7
Investigation into evaluating efficacy of percutaneous stenting versus angioplasty alone has yielded conflicting results. The VIENNA trial demonstrated a 37% restenosis rate at 12 months in those with SFA stenting versus a 64% restenosis rate for those with angioplasty alone.8 This was further supported by the RESILIENT trial, which demonstrated superiority with target vessel revascularization (TVR) at 12 months in those with SFA stenting over angioplasty alone.9 It is important to note that the RESILIENT results were primarily from TASC A and B lesions, with significantly higher crossover than previous studies. In contrast, the FAST trial demonstrated no difference in binary restenosis at 12 months between PTA and stenting compared to PTA alone.10 This finding was confirmed by a recent meta-analysis, which concluded that while initial procedural success is higher with routine stenting, there was no detectable difference in restenosis or TVR in long-term follow up.11 Stenting of the SFA for TASC A and B lesions is currently recommended only as a bailout procedure after technical failure of angioplasty.12
The last decade has ushered in many new endovascular treatment modalities for PVD including endovascular cryoplasty, cutting-balloon angioplasty, subintimal angioplasty, excisional atherectomy, excimer laser-assisted angioplasty, drug-eluting stents, biodegradable stents and e-PTFE covered self-expanding stents.13,14 The TASC II guidelines recommend endovascular treatment for TASC A and B lesions. Surgical revascularization has been the recommendation for TASC D lesions (lesion classifications are provided in Table 1). The guidelines are ambiguous as to how TASC C lesions are approached. There remains equipoise, with some recommending a trial of endovascular therapy first, while others suggest open surgical techniques as the frontline therapy. Though the guidelines recommend open surgery for the more severe cases (TASC C and D), many of these patients may benefit from less invasive endovascular treatments because they are not candidates for surgery due to a prohibitively high perioperative cardiovascular risk or other medical comorbidities. Many of these patients are denied any treatment, and thus frequently end up with the catastrophic consequence of limb loss.
Chronic total occlusions (CTOs) of the SFA are a particularly challenging lesion subset. Recanalization rates in CTOs are reported as > 85%. Pooled results also show 1- and 3-year patency rates for CTOs of 65% and 48% for PTA alone, and 73% and 64% for PTA/stent.15 There are no long-term data for PTA/stent, but the 5-year patency rates of PTA alone for stenosis and occlusion are 55% and 42%, respectively. Because of these success rates, many feel that patients with more extensive disease should be considered for percutaneous treatment and then referred for surgery if this approach fails. Bypass surgery with venous grafts must still be considered the most durable and extensively studied revascularization technique for patients with chronic limb ischemia and extensive disease of the SFA. The Bypass Surgery versus Angioplasty in Severe Ischemia of the Leg trial found that the rates of amputation-free survival after surgery and balloon angioplasty were similar for at least the first 2 years.18
Nitinol stents may be an effective alternative to surgical revascularization for longer lesions in patients who are poor candidates for surgery, such as those with severe coexisting cardiovascular conditions. Furthermore, stenting may be an option for patients without available saphenous vein grafts, since the 12-month patency data for stents are similar to those for prosthetic bypass grafts, and stenting has a considerably lower rate of complications. However, the endovascular approach seems justified as long as the rates of complications are low and the surgical target zone for the distal anastomosis of a potential secondary bypass operation remains unaffected by the interventional procedure.
This study, conducted at a major teaching hospital, evaluated the safety, efficacy and 1-year patency rates of the Viabahn expanded-PTFE (e-PTFE) stent grafts (WL Gore and Associates, Flagstaff, Arizona) in patients with SFA disease and Functional Class II and III claudication.
Methods
Thirty patients (32 limbs) were prospectively treated for activity and lifestyle-limiting claudication. All patients included in this study were symptomatic and refractory to maximal outpatient medical management including smoking cessation, use of cilostazol and exercise therapy. Asymptomatic patients, despite known severe SFA stenoses or occlusions, were not included in this investigation. Twenty-eight patients (93.33%) were Functional Class III–IV claudicants, while 2 patients (6.67%) presented with critical limb ischemia. None of the patients had tissue loss.
Traditional angioplasty and stenting techniques were employed in all patients. During the procedure, these patients received the Viabahn e-PTFE stent graft. Access for the intervention was obtained from the contralateral route in 22 patients (73.3%), via the antegrade ipsilateral route in 4 patients (13.3%), and via the ipsilateral popliteal approach in 6 patients (20%). No stent grafts Results
The mean age of the patients was 58.4 years. In all, there were 12 women (40%) and 18 men (60%). Five of the patients (16.67%) were diabetic. The technical success rate was 100%, with no in-hospital morbidity or mortality. There were no incidents of myocardial infarction, pseudoaneurysm, groin infection or death. One patient (3.3%) did have stent thrombosis at 4 months. The patient presented with acute limb ischemia and was treated with an open surgical approach using an autologous vein for a femoral-popliteal bypass procedure. The angiogram was consistent with a thrombotic occlusion of the stent graft, and no attempt was made to perform thrombectomy as an alternative treatment strategy. The mean preprocedure ABI was 0.54, and the mean SFA length of occlusion was 15.4 cm. The mean stented length was 24.6 cm. The median stent diameter was 6 mm. On follow-up testing, the mean post-procedure ABI at 1 year was 0.76 (Figure 1), with a primary patency rate of 80% at 1 year. Silent asymptomatic occlusions were noted in 10% (3/30) of the patients. Restenosis was detected on duplex surveillance in 6.6% (2/30) of the patients, with subsequent TVR via PTA. The 1-year primary assisted patency rate was 86%.
Discussion
The advent of endovascular treatment modalities has heralded a new era in caring for those with PVD. However, early adoption was limited to those with milder forms of disease (short focal stenosis or occlusions). In addition, the poor results seen in the early days of PTA/stenting had resulted in less acceptance of this strategy as a primary form of treatment for the more severe cases. As stents were initially used provisionally for unfavorable PTA results, earlier studies may have had a bias against stenting.17 However, with the advancement in technology and the introduction of nitinol stents, as well as e-PTFE-lined stents, PTA/stenting can finally be applied as a primary treatment in a large number of patients.
Data have been scarce from randomized clinical trials comparing surgical bypass with percutaneous intervention. This can be attributed to the fact that the two procedures have been historically reserved for different patient subsets. In 2005, Adam et al published a randomized study of 452 patients evaluating the efficacy of angioplasty and surgery in patients with severe lower-extremity ischemia. In this study, the authors found no difference in amputation-free survival at 1 year.18 In contrast to this, Wolf et al conducted a multicenter, prospective randomized trial comparing PTA to bypass surgery in 263 male patients with iliac, femoral or popliteal obstruction. However, in the 56 patients with long SFA stenoses, the 1-year primary patency rates after PTA and surgery were 43% and 82%, respectively.19 The results of this study, however, suggest otherwise, even in the toughest subset of patients, and are more in line with results obtained by Shaikh et al.20 The primary and primary-assisted patency rates obtained at 1 year, 80% and 86%, respectively, are encouraging and comparable to autologous vein bypass surgery.
Long-term patency, however, continues to be an issue of concern with endovascular treatment in the SFA. Coverage of side branches that supply collaterals has also been suggested as a potential problem in using stent grafts in the SFA. In this small study, neither of these issues seemed to be a significant problem. Dual antiplatelet therapy was rigorously enforced and may have had a favorable impact on the low incidence of stent thrombosis (1/30 patients: 3.3%) in this study. The current generation of heparin-coated Viabahn stent grafts were not used in this study. The potential for further reducing thrombotic risk with heparin coating appears promising.
The anatomy of the SFA plays a major role in long-term success, or lack thereof, using endovascular intervention. The SFA is subject to extrinsic dynamic forces (compression, torsion, elongation) that predispose stents to restenosis and fracture.21–23 The Viabahn stent graft consists of an e-PTFE liner attached to an external nitinol stent structure with significant flexibility, which enables it to be more easily placed across tortuous segments of the SFA and conform more closely to the anatomy of the artery. The procedural success rate and 1-year primary and primary assisted patency rates seen in this study indicate that percutaneous e-PTFE stent grafting with the Viabahn stent graft is a viable treatment option for TASC D occlusions in the SFA in claudicants and the occasional patient with critical limb ischemia. Long-term data (> 5 years) in a larger patient cohort are necessary before definite conclusions can be drawn.
Study limitations. This is not a randomized study comparing stents with surgery. The number of patients enrolled in this single-center registry was small, and follow up, though 100%, was reported only for 1 year. In spite of these limitations, this study is thought-provoking and adds to the body of evidence that endovascular treatment for TASC D SFA lesions may not be farfetched, and a randomized, controlled trial comparing surgery and stenting for TASC C and D lesions is warranted to better define the preferred treatment approach for this difficult lesion subset.
_________________________
From the *Cardiology Fellowship, §Interventional Cardiology Fellowship, Banner Good Samaritan Medical Center and £Heart and Vascular Center of Arizona, Phoenix, Arizona.
The authors report no conflicts of interest regarding the content herein.
Manuscript submitted December 30, 2008, provisional acceptance given February 5, 2009, final version accepted February 16, 2009.
Address for correspondence: Nahel Farraj, DO, 7004 West Keim Dr., Glendale, AZ 85303. E-mail: nahelfarraj@yahoo.com
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