How RESILIENT is SFA Stenting?

Study results evaluating stenting of the superficial femoral artery (SFA) have been conflicting, with stent fractures playing a major role in patency loss. However, newer nitinol stents show more promise than previous-generation stents because of their flexibility and durability.

“Over the last 10 years, treatment approaches for peripheral arterial disease have evolved tremendously, starting with a push to use percutaneous balloon angioplasty. However, that seems to have been supplanted by an interest in stenting,” says Srinivas Iyengar, MD, an interventional cardiologist at the Bradenton Cardiology Center in Bradenton, Fla., and principal investigator of the OSPREY trial, which is investigating the Misago self-expanding nitinol stent (Terumo Medical) for the SFA.

In 2006, Shillinger et al published a study evaluating 104 patients who received either a self-expanding nitinol stent (Dynalink or Absolute, Abbott Vascular) or percutaneous transluminal angioplasty (PTA) (N Engl J Med 2006; 354:1879-1888). They concluded that their low fracture rate of 2 percent is “consistent with the hypothesis that differences in stent design may substantially influence the likelihood of fractures.”

The recent RESILIENT trial showed that stenting may trump PTA in the SFA, at least for medium-length lesions (Circ Cardiovasc Interv 2010;3:267-276). The trend toward stenting the SFA may be shifting the focus from other repair approaches, such as laser atherectomy, remote endarterectomy or PTA. While RESILIENT and other studies, like the Zilver PTX trial, have shown good patency rates with SFA stenting, Iyengar urges restraint in wholesale adoption of stenting over other techniques, due to the fact that stents often fracture or restenose.

Based on the RESILIENT trial, however, the FDA approved the LifeStent (Bard), a self-expanding nitinol stent, for medium-sized SFA lesions. (The median lesion length in the stenting arm was 71 mm.) Two other self-expanding stents are FDA-approved for the SFA: Viabahn (W. L. Gore) and IntraCoil (ev3). Yet, other stents are used off-label in the U.S. for the SFA, and the European Union has several more stents approved for this purpose.

The FDA has been hesitant to approve SFA stents because of their tendency to fracture and their high restenosis rates. In RESILIENT, John Laird, MD, medical director of the University of California Davis Vascular Center in Sacramento, Calif., and colleagues randomized 206 patients with obstructive lesions (up to 15 cm) in the SFA and/or proximal popliteal artery and intermittent claudication at a 2:1 ratio to receive either the stent or PTA.

At six and 12 months, patients in the stent arm had better target lesion revascularization—the trial’s primary endpoint, as well as better primary patency rates at 12 months. The stent fracture rate was 3.1 percent at 12 months, which the investigators wrote was comparatively low. “The RESILIENT trial results have made people less hesitant to use stents in the SFA,” says Laird.

Is stenting the answer?

The SFA is a “strange animal” because of its many complexities, says John D. Martin, MD, vascular surgeon and director of the Anne Arundel Medical Center Vascular Institute in Annapolis, Md. “SFA repair approaches are completely dependent on the extent of the disease, its location and its length,” he says.

While Martin prefers PTA for SFA repair, he says stenting becomes a viable option when PTA fails, especially for longer lesions that don’t respond well to PTA. In addition, stents become a “quick option” in cases of a recurrent lesion or a dissection.

Laird concurs that PTA works best for short-segment lesions that are less than 4 to 5 cm in length, but says nitinol stents show benefit in the treatment of medium length lesions (10 to 12 cm in length). He says that the second-generation self-expanding nitinol stents for femoral access offer more longitudinal flexibility “to reduce the likelihood of fracture,” while Martin says the helical pattern design of the LifeStent allows for the adjustment of the forces within the SFA.

Problems and alternatives

SFA Stent Trials Approved by the FDA

OSPREY will enroll 350 patients in the U.S. and in Japan to receive either balloon angioplasty or the Misago (Terumo Medical) self-expanding nitinol stent in the superficial femoral artery (SFA). COMPLETE SE SFA study will evaluate the Complete self-expanding nitinol stent (Medtronic) in the SFA and/or proximal popliteal arteries (PPA). STROLL will study the Smart self-expandable nitinol stent (Cordis). DURABILITY II will look at the Protégé EverFlex self-expanding nitinol stent (ev3) to treat lesions as long as 16 cm in the SFA or PPA. SUPERB will look at the Supera self-expanding nitinol stent (IDev Technologies).

Yet, stenting the SFA may not be ready to be considered the gold standard. “There is a wide disparity in terms of treatment of the SFA,” says Laird. “Everyone has their own approach, but the RESILIENT trial and other trials have shown that stents clearly are better than PTA alone for moderate length lesions. However, there hasn’t been a good comparison between atherectomy devices and PTA or atherectomy devices and stents.”

Iyengar adds, “In long lesions, patency rates have not been very good and patients with these lesions typically have repeat procedures to reopen the stents. We are still trying to find a stent with better restenosis rates.” He says there needs to be better options and/or stents for longer lesions and for lesions that have a dissection plane within the SFA.

At the 270-bed Anne Arundel Medical Center, almost 1,000 interventions are performed annually—60 percent endovascular and 40 percent open procedures. Martin says remote endarterectomy, a less invasive technique exposing the common femoral artery and proximal portion of the SFA, may be best for longer occlusions.

Remote endarterectomy achieves debulking of the entire segment of the artery and helps re-establish flow with a minimal incision. The approach has shown patency rates that are equivalent to above-the-knee femoropopliteal bypass surgery—60 to 70 percent at three years with a primary assisted patency rate of 80 percent. The approach also can result in a shorter length of stay and lower morbidity rates.

“We found patency rates are better with remote endarterectomy than when we have done long-suboptimal PTA down the entire length of the SFA or SFA stenting down the outer length of the leg,” says Martin. “Remote endarterectomy is the best option for patients not undergoing femoropopliteal bypass—particularly over PTA.”

While PTA has been accepted as the standard of care for patients with longer lesions in the SFA, this technique has a high risk for complications such as wound infections, MI, graft failure and restenosis. “Even though the angioplasties are less expensive, the cost adds up if you have to repeat them,” says Martin.

Keeping down costs

As healthcare reform takes shape, there will be more of a focus on disease management and bundling, says Martin. “Performing multiple angioplasties and stenting procedures in a short-period of time is not going to be the most cost-effective approach to this disease. A shift toward bypass surgery may be in the future, as it costs less and adds more value to the healthcare dollar.”

Not much cost-effectiveness data exist regarding the new generation of nitinol stents. Past analyses have noted that stenting or balloon angioplasty is initially associated with lower costs compared with surgery, but that can even out depending on the need for treatment for restenosis and fractures. The RESILIENT investigators did not perform a cost-effectiveness analysis.

Nevertheless, Laird concludes: “We can feel more comfortable deploying stents knowing that we will get good results, that the fracture rate will be low and that our patient outcomes will be quite healthy at 12 months.”