In September, the US Food and Drug Administration approved the Complete SE (self-expanding) vascular stent for use in the lower extremities, specifically the superficial femoral artery (SFA) and proximal popliteal artery (PPA). Vascular Disease Management spoke about the device and the Complete SE SFA study with study principal investigator John Laird, MD, medical director and professor of medicine at UC Davis Vascular Center in Sacramento, California.
Q: Please give an overview of the Complete SE SFA study.
A: The Complete SE SFA study was a prospective multicenter single-armed trial that was conducted at 28 sites around the world — 23 in the United States, 2 in Belgium, and 3 in Germany. We’re evaluating the complete SE stent for lesions in the SFA and the PPA. Lesion lengths that were treated were lesions greater than 40 mm in diameter and less than 140 mm in length by visual estimate, which is similar to previous SFA stent trials, which included lesion length in the moderate range.
Ultimately 196 patients were enrolled in the trial and 214 lesions were treated. The study parameters gave the option of treating patients who had two lesions in the SFA as long as the cumulative lesion lengths were not greater than that 140 upper threshold. Patients who were enrolled in the trial had moderate to severe intermittent claudication or ischemic rest pain. We did not include patients that had ischemic ulceration or gangrene (Rutherford categories V or VI).
Q: Were there any remarkable characteristics or demographics in that patient population?
A: It turns out that we included patients with extensive SFA calcification; 91% of the patients had either moderate or severe calcification, graded by the core laboratory. Almost 30% of patients had chronic total occlusion, so we had fairly complex lesion subsets.
Q: What do you think the most important results of the study were?
A: The technical success rate was extremely high with the Complete SE stent — 99.6% of the stents were delivered and deployed accurately — and I think that’s one of the strong features of this stent. The triaxial stent delivery system with a stabilizing sheath allows for very precise deployment.
The actual acute lesion success, meaning successful deployment of the stent with less than 30% residual narrowing was also high at 90% and the primary endpoint of the trial — the primary patency at 12 months — was 72.6%.
It’s important to note how this primary patency was derived. It was derived by the actual data that was collected rather than by Kaplan-Meier curve analysis so basically we looked at all the patients who has 12 month follow up data even if their data was accumulated outside that 12-month time window and did a direct calculation of primary patency, which is different from how patency has been determined in some of the SFA stent trials where Kaplan-Meier curve analysis was perfomed.
Other important outcomes from the study were that there were no stent fractures identified at 12 months on plain film radiograph—both straight and bent knee. Also, the clinical outcomes were excellent. The need for clinically driven target lesion revascularization was only 8.4% at 12 months and 83% of patients were Rutherford category 0 or I at their 12-month follow-up time period.
Q: Were there any results that were surprising or maybe didn’t turn out as well as you might have hoped?
A: The surprising result was that the fracture rate was actually zero with the stent in the trial, which is surprising in a good way. The initial core lab assessment suggested possible type-1 stent fractures, meaning a single-tine fracture.
However, when we actually looked at these very carefully and looked at all of the images over time and then compared the appearance of the stent with some benchtop tests we realized that what was initially thought to be a type-1 fracture was actually a deformation or indentation of some of the stent rings by the heavily calcified lesions that were present and in fact when we did look very carefully, there were no clear-cut fractures and certainty no complex type-3 or type-4 fractures in this trial, so I think that’s a surprising and very favorable outcome, particularly given the highly calcified lesions that were treated as part of the study.
Q: Did you come across any potential limitations of the Complete SE?
A: The obvious limitation is that this is a single-arm registry as opposed to a randomized trial, so we cannot make any comparisons between the results of this stent with some of the other SFA devices that have been tested. When one tries to make these comparisons, one has to keep in mind that lesions were different, patients were different in the different trials and the analyses was different. Our assessment of patency was different than the assessment of patency in many of the other clinical trials where Kaplan-Meier curves were used.
The other limitation of this trial is that the lesions ended up being relatively short (mean lesion length was only around 6 cm) which is very consistent with many of the other SFA stent trials and the drug-eluting balloon trials. Whenever you have 14 cm or 15 cm as your upper lesion length, you typically end up with mean lesion lengths around 6 cm to 8 cm. So we can’t really make any strong recommendations about use of this stent or other stents for lesions longer than 15 cm. We only know that it performs well for these kinds of medium-length lesions.
Q: Are there any unmet needs or challenges for vascular specialists that might be met by this device?
A: The precision of deployment is a real plus for this device; with the triaxial delivery system including the stabilizing sheath outside the stent you can deploy the stent with great precision. I think it’s encouraging to know that there were no fractures with the stent despite its use in heavily calcified lesions.
It is hard to know how the stent stacks up against the many other stents that are available for use within the SFA including several that are FDA approved for this vascular bed. We have to keep in mind the differences in the trial designs and the methods of outcome reporting. I think it’s also important to recognize that most of these trials only include lesions of up to 15 cm in length so we don’t know how well this and other devices perform for longer SFA lesions and long occlusions or for more complex lesions subsets.
John R. Laird, MD, is a medical director and professor of medicine at UC Davis Vascular Center in Sacramento, California. His practice focuses on interventions for carotid artery disease, abdominal and thoracic aortic aneurysmal disease, renal artery disease, and peripheral artery disease. Dr. Laird reports consultancy to Abbott Vascular, Bard, Boston Scientific Corporation, Covidien, and Medtronic as well as grants from W.L. Gore.