Momentum Builds for Lower Extremity Stenting
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| The Protégé EverFlex (ev3) is one of several stents for the superficial femoral artery currently being evaluated in clinical trials. |
Generally, stenting the iliac artery is associated with very few complications, regardless of the generation of the stent. The consensus is that stents are the best choice for treating iliac lesions—“almost exclusively,” according to John Laird, MD, an interventional cardiologist at the University of California-Davis Vascular Center.
Newer stent designs have allowed operators to enter smaller openings in a safer fashion due to their flexibility. In fact, interventionalists can now access both sides of the vasculature from one access point. They can bring the stent down and across the bifurcation, or Y-junction, of the iliac, according to Gary Ansel, MD, an interventional cardiologist at Riverside Methodist Hospital, Columbus, Ohio. The restenosis rates with stents in the iliac arteries are “extremely low, as stenting has reduced the need for surgery associated with aortoiliac disease and carries a very high patency rate,” Ansel says. In addition, stenting the iliac can be performed in an outpatient setting.
Safety and efficacy of stenting the iliac arteries is recognized by the available approved stents including Palmaz (Cordis), Smart (Cordis), Zilver (Abbott) and Intrastent (ev3).
Traditionally, stenting the superficial femoral arteries (SFAs) has been more problematic, but that is changing with newer-generation stents. Earlier-generation stents for the SFA had very high crush rates, leading to high readmission rates. In the last 10 years, nitinol tubular stents have achieved high adoption rates due to their ease of use and perceived superior outcomes compared to balloon angioplasty. SFA stenting also can be conducted in an outpatient setting, but these lesions tend to be long in length and smaller in diameter, resulting in the potential for higher restenosis rates than iliac stenting.
Stenting the SFA
A stent-graft from W.L. Gore and the Intracoil stent from IntraTherapeutics had previously been approved for stenting the SFA, but new momentum is building as favorable trial data emerge and more stents near or gain FDA-approval. In February, the LifeStent FlexStar (C.R. Bard) was the first stent to be approved for stenting the SFA and the proximal popliteal arteries. The Protégé EverFlex (ev3) is expected to get the nod from the FDA soon, and other stents currently being evaluated in clinical trials include Complete SE (Medtronic) Smart and Zilver PTX.Krishna Rocha-Singh, MD, an interventional cardiologist at Prairie Vascular Institute in Springfield, Ill., questions the clinical utility of the approved second-generation stents. He says that their restenosis and fracture rates, as defined in large prospective evaluations, are not clearly known, particularly in longer lesions.
Treatment in the SFA with balloon angioplasty typically becomes an option for patients with shorter lesions—less than 4 cm. Stents are most often used for medium-length lesions, between 4 and 15 cm; however, atherectomy devices also are used as an adjunct to angioplasty in certain lesions, specifically those near vessel inlets (ostium) or in the popliteal segment where there are concerns for stent implantation. “It is not unreasonable to stent longer lesions, but these patients typically have a higher rate of restenosis,” Ansel says.
One caveat about these management strategies is that no clear, established gold standard exists, Rocha-Singh says. “Unfortunately, the current FDA regulatory process for the treatment of SFA interventions in claudicants does not hold as a primary study endpoint clinical improvement; rather a surrogate of the device’s durability—restenosis—is used.”
As a result, the Centers for Medicare & Medicaid Services (CMS), which currently reimburses for stenting these vascular beds, launched a review in July 2008 to consider the historical context of clinical practice standards and evidence supporting the use of peripheral stenting and vascular intervention in peripheral arterial disease (PAD). CMS has sent “a clear message through the AHRQ [Agency for Healthcare Research and Quality] mechanism that it is going to scrutinize current clinical practices, and is demanding clinically relevant trials,” Rocha-Singh says. “Trials will have to show clinical relevance to the patient. CMS may not accept a surrogate endpoint that reflects device durability, as opposed to a trial endpoint which reflects clinical benefit to the patient.”
Rocha-Singh adds that the TACS I Guidelines and ACC/AHA PAD Guidelines are “very thin in terms of recommendations, because there were relatively little data at the time they were written. The more recently revised TASC II Guidelines, published in 2005, also are behind the times because the techniques and technologies for treatment of these patients are moving so quickly.”
While no head-to-head comparisons currently exist, the SUPER UK trial is currently underway in the U.K. and is scheduled to conclude later this year. SUPER is a prospective, randomized trial comparing the patency rate at one year after either percutaneous transluminal angioplasty or stent placement with the Smart stent in 150 patients with SFA. Secondary objectives include the evaluation of clinical status and quality of life at discharge, three, six, nine and 12 months after the procedure, and evaluation of the cost-effectiveness of both stenting and angioplasty. Considering previous cost-effectiveness analyses, Laird notes that angioplasty (either stent or balloon) has been associated with lower initial costs, compared to surgery, though there can be “some catch up, if the patients need to return for additional treatment.”
As peripheral stenting has gained more attention from interventional cardiologists over the past decade, these practice considerations are now commonly weighed within the walls of the cardiology department, as disease in this vascular bed most often leads to complications in the coronary arteries. And, as the technologies and skill sets continue to improve, clinical efficacy questions linger as a final caveat to widespread adoption.