Use of the Complete SE Stent in the Superficial Femoral and Proximal Popliteal Arteries

In late September 2013, the U.S. FDA approved the Complete SE vascular stent (Medtronic) for use in the superficial femoral and proximal popliteal arteries. The approval was supported by the one-year results of the Complete SE SFA study, with principal investigators John Laird, MD, and Prof. Dierk Scheinert, MD. CLD asked Dr. Laird to share his experience in stenting the lower extremities.

What are the challenges of stenting the superficial femoral artery (SFA) and proximal popliteal arteries?

The challenge arises from the nature of the disease that we are trying to treat. The SFA and popliteal arteries are probably the most extensively diseased vessels in the body. 

There is often diffuse disease, and frequently we are treating long occlusions and heavily calcified arteries. Then there are the mechanical forces at play, with the twisting, stretching and compression of the artery as people walk and perform their normal activities of life. It is a very challenging environment for any treatment, particularly a mechanical prosthesis.

How were treatment efforts directed prior to stenting?

A variety of strategies have been tried over the years, primarily balloon angioplasty. Balloon angioplasty can work reasonably well for a focal lesion of less than 4 cm in length, but for anything longer, patency after balloon angioplasty is quite poor, probably only in the range of 30-40% over 12 months. There is a need for something better, and that is why, over the past several years, we have been looking at stents, with the hope of improving outcomes in the SFA.

What are some of the most important outcomes when evaluating stenting in these arteries?

One important outcome is initial technical success. Can the stent be delivered precisely, without complications? Can a good initial angiographic result be obtained? Patency afterwards is obviously very important. Is the long-term patency improved by placing the stent in the vessel, compared to balloon angioplasty alone? We also look at stent fracture, because with some of the earlier stents, there was a significant incidence of stent fracture and a few studies demonstrated reduced patency when stent fracture occurred. Finally, clinical outcomes are very important. Can the patient walk further? Has his ankle-brachial index (ABI) increased? Is there improvement in the patient’s Rutherford category? These outcomes are assessed along with other parameters to quantify the clinical benefit of the procedure.

Can you tell us about the Complete SE SFA study?

Complete SE SFA was a prospective, multi-center, single-arm trial of 196 patients. It was conducted at 28 sites: 23 in the United States, 2 in Belgium, and 3 in Germany. The study evaluated the Complete SE vascular stent in the SFA and the proximal popliteal arteries for patients with intermittent claudication or ischemia at rest. The Complete SE stent (Medtronic) is a self-expanding stent, laser cut from a tube of nitinol. It has a tri-axial delivery system, with an outer stabilizing sheath that allows the stent to be deployed very precisely. We treated lesions from 40 mm up to 140 mm in length, similar to most of the other SFA stent trials and drug-coated balloon trials. Stent diameters ranged from 6-8 mm and stent lengths up to 120 mm. Primary endpoint of the trial was patency by duplex ultrasound at 12 months. We looked at the usual secondary endpoints, including assisted patency, secondary patency, and clinical outcomes, including ABI, Rutherford category and results of a walking impairment questionnaire. Initial procedural results were excellent. Delivery of the stent was achieved in 99.6% of cases. Angiographic success was 90%, measured by < 30% residual stenosis. Primary patency at 12 months by duplex ultrasound, using a peak systolic velocity ratio of < 2, was 72.6%. The way we measured primary patency was more stringent than some of the other trials that used a Kaplan-Meier analysis. We looked at all patients who had 12-month follow-up with duplex ultrasound, even outside the window. As a result, the trial shows a slightly lower patency rate than what has been seen with some of the other trials. Clinically, patients did extremely well. The clinically driven target revascularization rate was only 8.4%. Very importantly, patients had improvement in their ABI from 0.7 to 0.9 at follow-up, and 83% of the patients in the study were Rutherford category zero or Rutherford category one at 12-month follow-up, meaning they were either asymptomatic or only had very mild claudication symptoms. In addition, what was unique about the Complete SE SFA trial was the high percentage of calcified lesions. Ninety-one percent (91%) of the lesions were either moderately or severely calcified.

Is the prevalence of calcified lesions due to the fact that patients are presenting later in their disease process?

There is no question that patients with peripheral artery disease are often diagnosed late in their course. Many of these patients are diabetic, and diabetics tend to have significant vessel calcification, whether vessel calcification in the wall of the artery, medial calcification, and/or the lesion itself. It certainly impacts our ability to obtain successful outcomes and longer-term patency.

How did the study compare to real-world practice?

Like many of the other SFA stent trials and drug-coated balloon trials, we are treating lesion lengths that are on the shorter side. Operators could treat lesions up to 14 cm in length as part of the trial, but the actual lesion lengths in the study were shorter; the mean lesion length was around 6 cm. That is typical for these types of trials, where most of the lesion  lengths tend to be in the 6-8 cm range. The results of these trials cannot be extrapolated to longer lesions, long SFA occlusions, or diffuse disease. However, what we can say is that for medium-length lesions, clinical outcomes with the Complete SE stent are excellent. Despite the fact that the trial had a high percentage of very calcified lesions, good patency was seen and zero stent fractures occurred.

What about diabetics?

About 45% of the patients in the trial were diabetic, which is typical for a claudication study. For some of the critical limb ischemia trials, the diabetic percentages will be a little higher, in the 60-70% range.

People often focus on the stent performance, but as you mention, delivery is crucial. What about the design of the Complete SE delivery system has proven helpful?

The Complete SE stent has a tri-axial design that allows for very precise stent deployment. There is an outer stabilizing sheath that prevents forward movement of stent during its release. 

Complete SE SFA trial one-year results were presented in early 2012. How has the trial impacted your thinking?

The results of the Complete SE study are in line with several of the other SFA stent trials, and I think these trials give us more comfort about stenting in the SFA and popliteal arteries. We can feel reassured that good clinical outcomes are achievable, and that the incidence of stent fracture is now very low with these devices. It was 0% in the Complete SE SFA trial. Even when SFA stent fracture occurs, it does not seem to be associated with adverse outcomes. Good patency rates are being seen with current devices, but clearly we would like our patency rates to be even higher. In the future we would like to be able to treat longer segment disease with higher patency rates than what we are currently seeing.  

Disclosure: Dr. Laird reports he is a consultant/advisory board member for Abbott Vascular, Bard Peripheral Vascular, Boston Scientific, Covidien, and Medtronic; and research support from W.L. Gore.

John Laird can be contacted at john.laird@ucdmc.ucdavis.edu

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Study at a Glance: The Complete SE SFA Trial

Results of the Complete SE SFA Study, an independently adjudicated, single-arm, multicenter trial that enrolled 196 patients at 28 sites in the United States and Europe, supported FDA approval in September 2013 of new superficial femoral artery (SFA) and proximal popliteal artery (PPA) indications for the Complete SE stent.

The study showed a clinically driven target lesion revascularization rate of 8.4 percent at 12 months. There were no in-hospital major adverse events (MAE) among study patients, and the total MAE rate at 12 months was 11%. The Kaplan-Meier estimate of primary patency at 360 days was 90.9 percent; at the time of the last duplex ultrasound assessment, at 553 days, primary patency was 72.5 percent. No stent fractures occurred through 12 months. 

Patient population (n=196):

• 45% of the patients had diabetes, and 67% had a Rutherford classification ≥3 at baseline.
• 50% of the treated lesions were located in the distal segment of the artery, and 91% were moderately or highly calcified.

Measures of clinical and functional effectiveness:

• At 30 days, >80% of the patients had achieved a Rutherford classification of 0 or 1, the favorable end of the 0-6 scale, and that benefit persisted through six months and one year of follow-up. 
• On walking assessment measures at 12 months, absolute improvement in impairment was 37%, distance was 32%, speed was 22% and stair climbing was 23%.
• Over the 12-month follow-up period, 65% of the patients showed an improvement of 0.15 or more on their ankle-brachial index (ABI) or toe-brachial index (TBI) scores. The mean ABI/TBI score at 12 months was 0.9.