Is drug-elution the solution for stenting in the SFA?


Some of the major drawbacks for superficial femoral artery (SFA) stenting include longer, multiple and more complex lesions, a large plaque burden prior to symptomology, triplanar intermittent mechanical stresses, low mean flow and shear stress, high thrombotic potential and phenotypic differences in vascular remodelling. So far, drug-eluting stents delay but have failed to conquer restenosis in the SFA according to the results of the SIROlimus Coated Cordis SMART Nitinol Self-expandable Stent for the Treatment of Obstructive Superficial Femoral Artery Disease (SIROCCO) II study. After the disappointment of the SIROCCO trial, there are early indications that drug elution may provide the solution for stenting in the SFA.

STRIDES Drug-Eluting Stent Trial

Abbott Vascular have recently announced that they will be testing their drug-eluting stent (DYNALINK-E) in the STRIDES trial. The DYNALINK-E uses the ABSOLUTE stent tested in the Vienna ABSOLUTE Study that showed improved primary patency rates at 12 months compared to balloon angioplasty with optional stenting in longer SFA lesions. The DYNALINK-E combines this stent with the EVAL polymer and the everolimus drug. This drug-eluting stent has a higher dose of drug and a slower elution rate than the SMART stent used in the SIROCCO trial that had very fast elution rates of one week versus one month in the coronaries. The Principal Investigator is Johannes Lammer and the STRIDES trial is looking at the performance of the DYNALINK-E stent in occlusion or critical stenosis of the SFA between 3 and 17cm in length. The study hopes to enrol 100 patients from 14 sites across Germany, Austria, Switzerland and Italy. The primary endpoint is restensosis at six months by duplex and secondary endpoints are angiographic late lumen loss and restenosis at 12 months as well as patency, survival, and amputation-free survival up to five years. There is also hope that the high fracture rate shown in the SIROCCO studies with the SMART stent will not be repeated. There were five reported stent fractures in SIROCCO II at six months and one additional stent fracture detected by the core lab via biplanar flat x-ray at 18 months. This resulted in a 10.7% stent fracture rate in SIROCCO II when a maximum of two stents were used vs. 19% in SIROCCO I when a maximum of three stents were used. In the ABSOLUTE study stent fractures occured in one of 68 stented limbs (1.8%).

ZILVER PTX Drug-Eluting Stent Trial

Another drug-eluting stent is the ZILVER PTX which is the ZILVER stent combined with paclitaxel without a polymer. Initial results of the ZILVER PTX trial were presented for the first time in the United States at the ISET meeting and in Europe at the Charing Cross International Symposium by Dr Michael Dake, professor and chairman of the department of radiology at the University of Virginia Health System.

Dake, the national Principal Investigator for Cook’s ZILVER PTX Drug-Eluting Stent Trial, presented important nine-month data on the first 60 patients in the randomized trial examining the safety of using Cook’s ZILVER PTX stent to treat blockages of the SFA. To reduce or prevent restenosis, the ZILVER PTX stent is coated with paclitaxel, a drug approved for clinical use as an anti-cancer agent. According to the company, this is the first trial ever to investigate paclitaxel-eluting stents in the SFA. The data was compiled based on enrollment in the pilot portion of the clinical investigation, which began March 2005 and was completed last year.

Dake reported that the ZILVER drug-eluting stent showed an equal major adverse event (MAE) rate to conventional angioplasty for treating SFA lesions at its six-month follow-up point. The ZILVER PTX stent also displayed a 0% fracture rate for 41 lesions at six months and 18 lesions at one year. Effectiveness of the device in treating lesions of the SFA will be shown in the pivotal trial, expected to start shortly in the US, enrolling 420 patients at 50 sites.

“I’m very excited to be presenting this nine-month data from the ZILVER PTX trial,” said Dake. “Drug-eluting technology combined with devices is the future of medical treatment. The results of this trial will be invaluable to the treatment of PAD in the future.”

Enrollment in the pivotal trial (Phase II) is expected to begin in 2007. Additionally, a ZILVER PTX registry is ongoing worldwide, collecting data to support this technology.