Patients treated with the Zilver PTX Drug-Eluting Peripheral Stent maintained clinical improvement at two years, according to interim results from the Zilver PTX Global Registry presented as a late-breaking clinical trial at the Society for Cardiovascular Angiography and Interventions (SCAI) 33rd Annual Scientific Sessions.

The prospective, single-arm study is ongoing to evaluate the drug-eluting stent for the treatment of peripheral artery disease (PAD). Results of a separate pivotal randomized study in a similar cohort of patients are expected to be available later this year.

In the meantime, this analysis includes 12-month follow-up data from 721 patients and 24-month follow-up data from 447 patients who received the Zilver PTX paclitaxel-coated stent in the superficial femoropopliteal artery (SFA), a major artery above the knee. The registry study was designed to evaluate stent integrity, event-free survival and freedom from target lesion revascularization.

PAD affects more than eight million people in the US and, if not treated, can limit the ability to walk and exercise, as well as place patients at risk for limb loss. PAD patients also have a greater chance of heart attack, stroke and death.

Although use of DES is common in the coronary arteries, the peripheral arteries, including those in the legs, experience different types of stress caused by walking and other movement. In some instances, blockages in these arteries are very difficult to treat, and may ultimately lead to limb amputation. The study is the third to evaluate the effectiveness of a drug-eluting stent outside of the coronary arteries, but the first to suggest clinical efficacy. The Zilver PTX is an investigational device.

The characteristics of the 787 patients who were enrolled and treated included restenosis of previously treated lesions in 24 per cent, in-stent restenosis in 14 per cent, and total occlusions in 38 per cent; 22 percent of patients had lesions longer than 15 cm. The mean lesion length was 10.0 ± 8.2 cm, the mean percent diameter stenosis was 84.6 ± 16.4 per cent, with an average of 2.2 Zilver PTX stents used per patient.

At 12 months, the event-free survival rate was 87.0 per cent, and freedom from target lesion revascularization was 90.5 per cent. X-ray evaluation found a very low rate of stent fractures, 1.5 percent of patients at 12 months. Patients available for 24-month follow-up had an event-free survival rate of 80.0 per cent, and freedom from target lesion revascularization was 83.3 per cent.

This low rate of target lesion revascularization translated into meaningful clinical improvement for the majority of patients, with both the average walking distance and average walking speed more than doubling following Zilver PTX stent implantation, and being sustained to two years. In addition there was a very good safety profile, and a very low rate of stent fractures.

"These interim data suggest this device is safe and efficacious for the treatment of SFA lesions," said William A Gray, FSCAI, who presented the study data and is associate professor of clinical medicine and director of endovascular services at Columbia University Medical Center/New York Presbyterian Hospital. "Prior attempts to demonstrate drug-eluting stent effectiveness using sirolimus or its analogues have fallen short, but the use of a paclitaxel-coated, non-polymeric stent appears to have improved the outcomes for patients who received this study stent. If these results are confirmed in the separate randomized study using the same device, it will be welcome news to patients who suffer from this disease."