Boost for stenting in the SFA

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Following on from the disappointing results from several studies (such as the Femoral Artery Stenting Trial [FAST]) that failed to show any clear benefit of stenting in the superficial femoral artery (SFA), there was better news for the proponents of stenting at the International Symposium on Endovascular Therapy (ISET), Miami, FL. The results from three studies revealed that stenting is a safe and effective treatment option for treating SFA lesions.

Dr Barry Katzen, Baptist Cardiovascular Institute, Miami, FL, reported positive 12-month data from a randomized study comparing the Edwards self-expanding LifeStent vs. angioplasty-alone in lesions involving the SFA &/or Proximal Popliteal Artery (RESILIENT).

The Edwards self-expanding LifeStent is a Nitinol with tantalum markers and boasts flexibility without kinking due to the helical design. A Phase I (Feasibility) study demonstrated excellent outcomes with the Nitinol stent design with no safety issues reported, 0% stent fractures and 90% clinical patency at 12% months.

The Phase II (Pivotal) study is randomised, prospective, multi-center study. The purpose of which is to evaluate safety and efficacy of the Edwards LifeStent NT compared to PTA-alone for the treatment of de novo or restenotic (non-stented) lesion(s) of the native SFA &/or proximal popliteal artery. Patients were randomized to control (PTA-alone) or treatment (PTA with stenting) on a 1:2 basis. Patients enrolled in the RESILIENT trial have occlusions/ stenosis =150mm. The first RESILIENT patient was enrolled in July 2004 and enrolment was completed in August 2006 (24 sites). Clinical follow-up occurs at 30 days, six months, 12 months, and annually for a maximum of three years. Safety endpoints for the study include periprocedural death, stroke, myocardial infarction, emergent surgical revascularisation, significant distal embolization in the target limb, and thrombosis in the target vessel. Efficacy endpoints for the study include vessel patency and target lesion/vessel revascularisation (TLR/TVR).

Inclusion criteria included: lifestyle-limiting claudication defined as rutherford category 1-3 (mild to severe claudication); the target lesion(s) must meet the following criteria de-novo or restenotic (stenosed, occluded, restenosed, or re-occluded) located within the native sfa and/or proximal popliteal artery; 3cm above the knee joint and 1cm below the origin of the profunda femoris artery; if the lesion(s) is restenosed or reoccluded; prior PTA-only treatment must have occurred >6 months prior to the study procedure; the target lesion(s) has angiographic evidence of stenosis or restenosis >50% or occlusion (by visual estimate) and is amenable to PTA-alone or PTA with primary stenting; the target vessel reference diameter is >4.0 mm and <6.5 mm (by visual estimate); the lesion or series of lesions has a total length <150mm; there is angiographic evidence of at least one vessel runoff to the foot; prior to enrollment/ randomization, access is obtained to the target vessel and the balloon (uninflated) is across the most distal target lesion. Thirty-day clinical success was 87.9% (n=51) in the PTA arm and 95.8% (n=138) in the stenting arm with primary patency (Duplex) 57.4% (n=27) in the PTA arm and 99.2% (n=118) in the stenting arm. Freedom from re-intervention was 58% (n=40) in the PTA arm and 99.4% (n=160) in the stenting arm. At six-months, clinical success was 56.8% in the PTA arm and 67.4% in the stenting arm with primary patency (Duplex) 41.2% in the PTA arm and 89.7% in the stenting arm. Freedom from re-intervention was 56.5% in the PTA arm and 94.6% in the stenting arm. The number of stent fractures was four (elongated stents) from 192 implanted stents (no. of patients 120), equating to a fracture rate (per evaluable stents) of 2.2% (data from VEITHsymposium 2006). The 12-month interim results revealed a freedom from intervention rate of 44.1% for the PTA arm and 81.5% in the stenting arm. Moreover, the number of stented subjects at 12-month follow-up was 81, with a total of 136 stents inplanted. The number of fractures reported was five (no clinical symptoms), equating to a fracture rate (per evaluable stents) of 3.7%. “The pivotal RESILIENT is complete and data analysis will provide level I evidence regarding PTA vs stenting in the SFA,” said Katzen. “Both 30-day and six month data is very promising regarding the benefit of stenting. The Phase II interim results demonstrate robust outcomes with a novel, flexible Nitinol stent design.” He added that at 12-months there were no safety issues, a low stent fracture rate and a clinical patency rate of 80%. Katzen concluded that future studies are planned to evaluate the FlexStar XL stent deliverability and deployment accuracy, and chronic efficacy of long (170mm) stents. ZILVER PTX Drug-Eluting Stent Trial

Also at ISET, Dr Michael Dake, 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 whether 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, professor and chairman of the department of radiology at the University of Virginia Health System. “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.

VIBRANT

Next, Dr Gary Ansel, an interventional cardiologist at Riverside Methodist Hospital, Columbus, OH, presented 30-days results from the VIaBahn veRsus bAre Nitinol stenT (VIBRANT) study. Sponsored by Gore, the study is a randomized, prospective, multi-center clinical trial intended to demonstrate patency superiority in the treatment of SFA lesions 8cm or longer with the GORE VIABAHN Endoprosthesis compared to bare Nitinol stents. Patients will be followed for a total of three years with patency surveillance via duplex ultrasound at one, six, 12, 24, and 36-month intervals. An independent core laboratory will interpret results of the follow-up ultrasound imaging. Approximately 150 patients will be entered into the study randomized to either the GORE VIABAHN Endoprosthesis or bare Nitinol stent. Study endpoints will be centered on primary and secondary patency -or the state of vessel blood flow – of the treated artery. Nationally, ten centers are participating in the study.

The GORE VIABAHN Endoprosthesis is constructed with a durable, reinforced, biocompatible, expanded polytetrafluoroethylene (ePTFE) liner attached to an external Nitinol stent structure. The self-expanding ePTFE/Nitinol device is designed to allow relining of luminal surfaces in tortuous arterial anatomy. In contrast, bare Nitinol stents commonly used in the SFA do not feature an inner lining and are composed solely of a metal scaffold. The flexibility of the GORE VIABAHN Endoprosthesis enables it to traverse tortuous areas such as the SFA and conform closely to the complex anatomy of the artery. Along with its flexibility, the GORE VIABAHN Endoprosthesis is engineered for strength and durability. According to the company, this strength and durability makes it well-suited to withstand the relentless forces and challenges of the SFA.

Ansel said that patients with complex SFA occlusive disease, treated with bare Nitinol stents or the Viabahn stent grafts have a low target lesion revascularisation rate at 30-days, demonstrating a good early safety profile. “The VIBRANT trial will allow physicians to determine whether adding a bypass-like covering to a stent will improve on the short and longer term results of bare metal stents.”

Date: Feb/2007

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