Medical Device Daily Associate Managing Editor

The first U.S. multicenter, prospective clinical trial to investigate the use of minimally invasive stent placement to treat severe peripheral arterial disease (PAD) below the knee has been cleared by the FDA, with its approval of an investigational device exemption (IDE) filed by the study's sponsors.

The study, sponsored by Viva Physicians (VPI; Rosemont, Illinois) and supported by a restricted educational grant from the maker of the stent, Abbott Laboratories (Abbott Park, Illinois), will be the first in the U.S. to evaluate the Xpert expandable nitinol stent in the blood vessels below the knee.

The Xpert is already cleared in the U.S. to treat blockages in the biliary ducts that carry digestive enzymes from the liver.

VPI submitted its IDE application to study the stent's use in the popliteal and tibial arteries below the knee to the FDA on Feb. 7.

“The Xpert stent is particularly appropriate for this trial because it is the only self-expanding stent that comes in a variety of sizes small enough to treat the blood vessels below the knee,” James Joye, MD, principal investigator for the XCELL trial, told Medical Device Daily.

Joye's center,El Camino Hospital (Mountain View, California), will be among the sites participating in the study, which is also the first study that VPI has undertaken since its formation in 2002.

“The study is also important because it is one of only a very few independent, physician-sponsored efforts,” noted Joye. “VPI set the protocol, applied for the IDE and is responsible for data collection, evaluation and reporting.”

He said that the primary endpoint of the XCELL study is avoidance of major amputation at 12-months follow-up after treatment.

Questioned by MDD as to why VPI chose the Xpert for its first study, Joye said the answer could be broken down into three parts.

First, he noted that critical limb ischemia is an important disease state, “whose options for treatment are not adequately appreciated by physicians and patients.”

It is estimated that 25 million people suffer from blockages in the arteries of the lower leg, and “those with advanced disease may be poor candidates for surgery and have few treatment options,” Joye said. “Many are at high risk of losing a limb. This is an important trial to expand patient treatment options, increase physician awareness and take an important step forward in preventing amputation.”

Secondly, Joye noted that the Xpert is, in his opinion, the first stent to be designed “potentially for the purpose of treating arteries below the knee,” particularly given the small vessel sizes – 2 mm to 4 mm – in these areas.

Finally, he said his group views this technology “as a stepping stone to future applications on a platform such as [the Xpert], wherein we could combine, potentially, stent technology with other medicated applications like we've seen in the heart, for example.”

The Xpert self-expanding stent is a tiny cylinder made of metal mesh that is placed in the artery during a minimally invasive interventional procedure. In the technique, a catheter is inserted through a small nick in the skin and threaded through the blood vessels to the site of the blockage under X-ray guidance. The stent is deployed through the catheter and expanded to prop open the diseased artery.

According to Joye, the procedure only takes from 60 to 90 minutes to perform and, for many of these patients, it can be performed on an outpatient basis.

Prior to this stent technology, Joye said doctors have had several options for treating PAD below the knee, including angioplasty, cutting balloons, and cryoplasty. While all of these have been successful in treating critical limb ischemia, he said secondary issues still could be better served.

He said that while the main tenet of this study is “does this application using this stent in this group of patients result in limb salvage?” several secondary questions including how quickly do the wounds heal?, what kind of quality of life do these patients have?, and does the vessel stay open longer?, cry out for better answers. These secondary issues are all things Joye and the other investigators hope this trial will address in a more satisfactory way than current surgical options are able to do.

The study is expected to enroll 140 patients at about a dozen centers, according to Joye. He said the patients will not be randomized because it would not be ethical to randomize patients to something else, particularly because this is a group in which 90% of patients end up as amputees. The results will be compared to what the results of surgical bypasses have been below the knee, an area in which a comprehensive amount of scientific literature exists.

He said if all goes well, the investigators hope to complete enrollment in the trial by the end of the year.

VPI said the XCELL study meets the group's goal of executing trials that will support standards of practice. The organization said it is also is involved in developing objective performance criteria for limb salvage and interventions for lower extremity peripheral arterial disease, and is investigating strategies to deal with in-stent restenosis and acute stroke intervention.

VPI describes itself as a not-for-profit organization involved in PAD education, research and therapy.

In a related technology announcement, Cordis Endovascular (Warren, New Jersey) this week reported nationwide introduction of what it called two “breakthrough devices,” Frontrunner XP CTO and Outback LTD Re-Entry Catheters to treat artery blockages in the lower leg.

Both devices facilitate placement of a guidewire in minimally invasive procedures such as angioplasty and stenting of chronic total occlusions (CTO). A CTO is a complete or nearly complete blockage of an artery that can lead to surgery or lower leg amputation.

In order to treat CTOs with less-invasive methods, a doctor must first cross through the blockage. The reentry catheters allow physicians to break through complete blockages allowing treatment with stents or balloons. By using these catheters, patients may avoid having to undergo difficult surgeries or even amputations, Cordis said.

“With the nationwide availability of these devices, many patients with diabetes or peripheral artery disease may now be able to avoid having amputations due to serious blockages in their legs,” said Dr. Dennis Donohoe, wordwide vice president, clinical and regulatory affairs for Cordis.

More than 20 million Americans who suffer from diabetes are at risk of amputation of a lower limb. In addition, patients without diabetes who have peripheral vascular disease may also develop CTOs. About 9 million people in the U.S. have peripheral vascular disease, and only 725,000 people are diagnosed annually and less than half receive either surgical or endovascular treatment.

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