3-Year Results of the RESILIENT Trial With the LifeStent: Are the Results of SFA Stents Durable?

What are the problems in stenting the superficial femoral and popliteal arteries?

A major source of concern over the years has been the effects of putting a permanent metal prosthesis in a blood vessel that has such dynamic movement, with flexion, stretching, torsion and compression. There has also been the concern about the potential for that device to fatigue and fracture. The chronic injury created by a device in this very dynamic vessel could also lead to a higher risk of restenosis. With lifelong injury occurring because of the presence of the stent, late or delayed restenosis has been a concern. Once in-stent restenosis occurs, then it becomes a much more difficult problem to treat versus a de novo vessel. 

Are the types of lesions that occur in this vessel more calcified?

The superficial femoral artery (SFA) tends to have a high percentage of calcified lesions; it’s probably the most heavily diseased vessel in the body. In the distal SFA near the adductor canal, it is very common to have very calcified, very tough lesions to treat. Total occlusions are also common in this vessel.

Why is the LifeStent (Bard Peripheral Vascular) being studied for use in the SFA?

The LifeStent is a second-generation nitinol stent that is more flexible because of both the orientation of the stent’s inner connections and its helical design. It is very flexible and it was thought, at least at the time the RESILIENT trial was started, that it would also be more resistant to fracture because of its flexibility.

This is a bare-metal stent. Why not a drug-eluting stent?

At the time the trial was designed, there were no drug-eluting stents that had been developed yet for peripheral vascular use. In fact, at that time, there was really only one stent approved by the FDA for femoral use, and that was an older coil stent design, the Intercoil stent, which is no longer commercially available. 

First things first, we needed a good stent that could be approved by the FDA for femoral use; which now, because of the RESILIENT trial, we have. Along the way, there have been attempts to develop or investigate drug-eluting stents in the femoral arteries, and for the most part, that has been frustrating and not as successful as in the coronaries. The only drug-eluting stent that has worked so far has been the Cook Zilver PTX paclitaxel-coated stent, which received FDA approval in November 2012.

Can you tell us about the RESILIENT trial (A Randomized Study Comparing the Edwards Self-ExpandIng LifeStent Versus Angioplasty-alone In LEsions INvolving The SFA and/or Proximal Popliteal Arteries)?

RESILIENT is a prospective, randomized, controlled, multi-center trial comparing balloon angioplasty plus the LifeStent (Bard Peripheral Vascular) to balloon angioplasty alone. The trial enrolled 206 patients needing treatment for lesions up to 15 cm in length in the SFA or proximal popliteal arteries. At 12 months, the LifeStent was far superior to balloon angioplasty with regard to target lesion revascularization and had better patency by duplex ultrasound.¹ At three years, we found that the initial benefit was maintained.² The three-year results with the stent were excellent; there continued to be benefit of stenting over angioplasty, and there were actually very few episodes of late restenosis outside of two years, so there did not seem to be a lot of late catch up or delayed restenosis in the stents, which allayed some of our concerns about putting a permanent implant in the femoral artery.

Any problems with fracture?

The fracture rate at 12 months was 3.1%; there were nine fractures identified at 12 months. We looked again at 18 months and found three additional fractures, for a total of 12 fractures and an overall fracture rate in the study of 4.2%. We did not look beyond 18 months, so do not have a three-year fracture rate. What we learned early on was that the first-generation delivery system that came with the LifeStent made it very easy to stretch out or elongate the stent during deployment, and most of those serious fractures occurred because of elongation of the stent during deployment. With the newer delivery system, that is much less of an issue. 

The LifeStent is a self-expanding stent. What is the advantage of that in the SFA?

Balloon-expandable stents are definitely not advised for the SFA or popliteal arteries, because they can be compressed or crushed, and they do not bounce back. If you take a balloon-expandable stent and squeeze it, it will flatten out and won’t expand open again, which is not a viable solution for the SFA or popliteal arteries where there is all this movement and flexing, twisting, stretching, and bending. So a self-expanding nitinol stent that is crush-resistant is best, and most or all of the nitinol stents now meet these criteria. 

How have the trial results changed your practice?

It has made me more comfortable about putting stents in the SFA. The one qualifier is that the study only looked at lesion lengths up to 15 centimeters, so it does not mean we can put in a full metal jacket of stent in the SFA and expect the results to be good. However, for appropriate lesions in the moderate length, up to 15 centimeters, the results with this stent were good. I now feel very comfortable using the stent for these types of lesions. I think others as well feel more comfortable stenting SFAs based on the results of this study.

What do you think about drug-eluting balloons?

There is a great deal of excitement about drug-eluting balloons and most, if not all, of the DEBs use paclitaxel, which is a drug we are all familiar with from the coronary drug-eluting stent experience. Paclitaxel is combined with a carrier or a molecule on the balloon to allow the drug to be delivered into the vessel wall. There have been a number of randomized trials now that have shown that drug-eluting balloons work better than regular balloons in terms of reducing the risk of restenosis, so that is very exciting. For those who are still reluctant to put in a metal stent, a permanent implant, into the SFA, drug-eluting balloons are a very interesting option. At the end of the day, the results in terms of patency at 12 months with a drug-eluting balloon versus a nitinol stent, are probably the same; you just get that result without having to put a stent in. In some cases, it might be preferred.

We don’t have the data yet.

We don’t have a direct comparison of drug-eluting balloons with stents. All we have is a comparison of drug-eluting balloons with regular balloons, where drug-eluting balloons clearly work better. If you look at the data, the outcomes look similar to what you would get with a stent. Big drug-eluting balloon studies are still underway in the United States. C.R. Bard bought a company called Lutonix that just completed a large U.S. randomized trial and Medtronic also has an ongoing U.S. trial comparing drug-eluting balloons with regular balloons. We will get some additional information in the next year or two. 

Dr. John Laird can be contacted at John.Laird@ucdmc.ucdavis.edu.

References and recommended reading

1. Laird JR, Katzen BT, Scheinert D, Lammer J, Carpenter J, Buchbinder M, et al. Nitinol stent implantation versus balloon angioplasty for lesions in the superficial femoral artery and proximal popliteal artery: twelve-month results from the RESILIENT randomized trial. Circ Cardiovasc Interv. 2010 Jun 1; 3(3): 267-276. doi: 10.1161/CIRCINTERVENTIONS.109.903468.
2. Laird JR, Katzen BT, Scheinert D, Lammer J, Carpenter J, Buchbinder M, et al. Nitinol stent implantation vs. balloon angioplasty for lesions in the superficial femoral and proximal popliteal arteries of patients with claudication: three-year follow-up from the RESILIENT randomized trial. J Endovasc Ther. 2012 Feb;19(1):1-9. doi: 10.1583/11-3627.1.