January 27, 2007 -- The Protégé® RX from eV3, Inc. was approved this week by the U.S. Food and Drug Administration, making it the fifth carotid stent available for marketing in the U.S. The Protégé is a self-expanding Nitinol stent which is part of a carotid stent system when paired with eV3's SpideRX® Embolic Protection Device. Carotid stenting systems comprise two actual devices: the stent itself and a separate but compatible filter, which helps prevent emboli that may be dislodged during stent placement from traveling upstream into the brain, causing a stroke.

eV3's Protégé RX/SpideRX system is similar to other carotid systems in certain respects -- the stent itself is made of self-expanding Nitinol, and it is available on what is known as a rapid exchange platform, or RX. Rapid exchange allows a single operator to perform the stent deployment; without an RX capability, stenting becomes a four-handed procedure, requiring an interventionalist and a trained assistant. The Protégé stent is also offered in both a straight and tapered version for a better fit in the carotid bifurcation.

According to Stacy Enxing Seng, President of ev3's Cardio Peripheral Division, the Protégé RX/SPIDER carotid stent system offers several advantages over the current systems on the market. One is "predictable deployment". Ms. Seng described these features to Angioplasty.Org:

"We have this proprietary EX.P.R.T.™ release technology on all of our self-expanding stents and that eliminates premature deployment or 'jumping'. It is a very exact placement system. The second aspect that is more developed and helpful to the physician is the visibility of the system. It has Tantalum markers that enhance the visibility and that also assist with precise positioning.

"On the embolic protection device, without question, the most significant difference that is very distinct is the guide wire of choice. What this allows is that physicians can use any .014" guide wire that they choose, whereas many of the other embolic protection systems are actually on their own dedicated wires, such as the Abbott system, where effectively, you have to use their wire, which doesn't give physicians the flexibility to use their everyday work-horse wire."

The whole field of carotid artery stenting (CAS) is relatively new; the first carotid stent was approved in the U.S. only a little over two years ago. Stenting competes with the invasive surgical procedure used to open the carotids, called carotid artery endarterectomy (CAE), which has been in practice for decades. Stent systems were approved by the FDA because the clinical trials run by the manufacturers showed equivalent results with surgery for the patient populations studied.

At present, the indications for carotid stenting are limited to the populations in whom it has been proven most effective. For example, the approved indications for the Protégé carotid stent are in patients who:

• have medical problems or anatomic abnormalities that would put them at high risk for adverse events from the surgical procedure of carotid endarterectomy, AND
• have had a stroke (are symptomatic) and have at least a moderate (> 50%) blockage in the blood vessels of the neck, OR
• have not had a stroke (are asymptomatic) but have a very tight (> 80%) blockage in the vessels of the neck
• the reference vessel diameter at the target lesion (blockage) must be within the range of 4.5mm-9.5mm

As part of its new emphasis on post-market surveillance, the FDA is also requiring eV3 to do three-years of follow-up for the 419 patients who were in the CREATE clinical trial which led to approval. Additionally the company will have to follow-up 1,500 new patients as the device is used: 1,000 of them will have follow-up for 30 days; the remaining 500 for a year.

Safety of all medical devices has been a concern recently, and specifically with carotid stenting, there were a number of questions raised by two European studies, published in October 2006: the EVA-3S and SPACE trials, both of which showed a poorer outcome for patients treated with carotid stents vs. surgery. These results were radically different than those seen in large studies, such as SAPPHIRE and BEACH, which showed equivalence between the two methods.

The publication of these negative studies raised much controversy, and interventionalists who have been working with carotid stenting for a decade, like Dr. Gary M. Ansel of Riverside Methodist Hospital in Columbus, Ohio, were not at all pleased with news headlines, such as "Study Warns Of Dangers Of Stents To Prevent Strokes" and "Neck Stents Present Stroke Risk".

As Dr. Ansel told Angioplasty.Org, the two European trials were:

"...poorly run, poorly performed, with operators that didn't have a lot of experience, utilizing embolic protection on a random basis, with not good antiplatelet therapy. We'd expect poor results from those trials, yet they got all the headlines. SAPPHIRE was a very well-done CORE-lab controlled study. Investigators had plenty of experience getting into that trial and you had the exact opposite results. You had a non-surgical therapy that had a lower complication rate, it had the same amount of prevention of stroke rate as open surgery, and it had a lower re-intervention rate."

Indeed, some of the physicians who did carotid stenting in the European trials had done less than ten procedures, and the embolic protection filter devices that are mandatory in the U.S. were not used in many of the patients. Furthermore, antiplatelet therapy to keep blood clots from forming immediately post-stenting was not uniformly prescribed.

A current trial, now enrolling patients, called CREST, is a very large multi-center trial and in the view of many physicians, both interventional and surgical, will be a watershed study on whether stents and surgery are equivalent.

For now, the clinical trials that have been judged by the FDA to be valid have shown that stenting can be an effective and safe procedure for the patient population at high risk for surgery. As second-generation devices come on the market, the population will no doubt expand.

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