New Stent Performs at 6- And 12-Month Follow-Up

Elsevier Global Medical News

SAN DIEGO -- The Zilver PTX Drug-Eluting Peripheral Stent appears to have excellent durability in the superficial femoral artery at 6- and 12-month follow-up, according to the interim results from a large registry study.

Manufactured by Cook Inc., the Zilver PTX is an investigational self-expanding nitinol stent coated with paclitaxel.

"It does not use a polymer or binder," Dr. Michael D. Dake said at the Vascular Annual Meeting. "This differentiates it from most of the drug-eluting stents in practice today."

Dr.Dake reported on the interim results from the registry arm of the study, which included 790 patients who were treated at 30 sites in Europe, Russia, Canada, and Korea. A randomized study that intends to enroll 400 patients is currently underway in the United States, Japan, and Germany.

The registry trial involved treatment of the above-the-knee femoropopliteal artery from a point 1 cm below the bifurcation to a point above the medial femoral epicondyle. The reference vessel diameters were 4-9 mm.

"The trial included all comers," Dr. Dake, chairman of the department of radiology at the University of Virginia Health System, Charlottesville, and the study's principal investigator.

"There was no lesion length limitation. Up to four stents per patient could be placed," Dr. Dake added.

The mean age of the study patients was 67 years and most (73%) were men. More than one-third (36%) had diabetes, 55% had high cholesterol, 80% had hypertension, and 79% were past or current smokers.

The mean lesion length was 9.6 cm, the reference vessel diameter was 5.4 mm, and the mean diameter of stenosis was 85%. The average number of stents placed per lesion was 1.9.

"These were very complex cases, with almost 45% being TransAtlantic InterSociety Consensus [TASC] C and D lesions," said Dr. Dake, who is also a professor of radiology at the university. "Roughly one-third of the patients were total occlusions."

He reported 6-month follow-up data on 435 patients and 12-month follow-up data on 200 patients.

In terms of stent integrity, the fracture rate was 1% at 6 months (8 of 825 stents) and 2% at 12 months (11 of 547 stents). "Actually these are fractures pending confirmation, so the rate may actually be less than that, but at least it's in the low single digits," he said.

Event-free survival was defined as freedom from death, amputation, revascularization, or worsening of Rutherford classification by two classes or to a class 5 or 6. The event-free survival was 94% at 6 months and 84% at 12 months.

Stent effectiveness as measured by the clinical end point of freedom from target lesion revascularization, defined as clinically driven reintervention or greater than a 50% stenosis within the treated segment, was 96% at 6 months and 88% at 12 months.

Clinical outcomes, as measured by ankle brachial index, Rutherford score, walking distance score, and walking speed score, demonstrated significant improvements at 6 and 12 months, compared with preprocedure values.

"There are no safety concerns apparent at this time with the Zilver PTX stent," Dr. Dake concluded.

"In terms oeffectiveness, this appears favorable, with the initial results appearing better than expected for complex TASC C and D lesions, occlusions, in-stent restenosis, and lesions longer than 7 cm."

Dr. Dake disclosed that he receives research support from Cook Inc., which sponsored the trial.

When asked to comment on this story, Dr. Frank Pomposelli, who is the chief of vascular and endovascular surgery at Beth Israel Deaconess Medical Center, Boston, stated: "The results of this study offer hope for one of the most challenging problems in endovascular treatment of the superficial femoral artery, namely the high rate of early restenosis. The results of this study demonstrate outcomes that may have less than half the rate of restenosis seen with PTA alone and perhaps 25% better than PTA with stenting.

"However, I am disappointed that the results do not include calculations of actual patency since 'clinically driven' reintervention can be imprecise and subjective making comparisons to other therapies difficult compared to 'hard' end points like patency and limb salvage.

"For example, in claudicants the improved exercise tolerance with successful stenting may lead to more exercise and continued clinical improvement even after the stented vessel reoccludes. For tissue loss, once the lesion heals, symptoms may abate and not necessarily return with stent occlusion or stenosis.

"Nonetheless, the current results are encouraging and I look forward to the final analysis."

Dr. Pomposelli is also an associate professor of surgery at Harvard Medical School, and an associate medical editor of Vascular Specialist