Closed-Cell Carotid Stents Edge Open-Cell Models

By Mitchell L. Zoler

PHILADELPHIA -- Closed-cell stents were found to be more effective than open-cell stents for preventing periprocedural adverse events in patients with symptomatic carotid-artery disease from a registry of about 700 patients, Dr. Joseph P. Hart said at the Vascular Annual Meeting, sponsored by the Society for Vascular Surgery.

"We're not just trying to establish flow in the carotid. We're also trying to prevent current and future embolization, and the thought [behind] closed-cell stents is that they do a better job of keeping debris out of the flow channel and thus out of the brain," said Dr. Hart, who is a vascular surgeon at the University of Rochester (N.Y.).

"It's a very attractive hypothesis, but it's based on a relatively small number of events. An analysis of a larger series of patients would be valuable," commented Dr. Robert Hobson, a professor of vascular surgery at the University of Medicine and Dentistry of New Jersey in Newark.

The categorization of stents as open or closed cell refers to the pattern of metal wires that is used to make up a stent's structure. Open-cell stents are made of parallel wire loops with few wires that cross these loops. The resulting pattern has lots of open spaces.

In contrast, closed-cell stents have many crossing wires, a design that creates much smaller spaces between the wires. In theory, closed cells should do a better job of trapping plaque against the arterial wall and should prevent pieces of plaque from protruding between the stent's struts and into the carotid lumen.

The registry data analyzed by Dr. Hart and his associates came from two Belgian hospitals: St. Blasius in Dendermonde, and Imelda Hospital in Bonheiden.

The researchers reviewed the outcomes of 701 patients who had a carotid stent successfully placed during January 2001 through August 2005.

The series studied included 304 patients with symptoms of carotid-artery stenosis, and 397 patients who were asymptomatic.

The incidence of death, stroke, or transient ischemic attack during the first 30 days following stent placement was 3.7% among all 701 patients.

Patients who received close- or open-cell stents had no significant difference in their periprocedural adverse-event rate for the entire patient series.

But in an analysis that focused only on symptomatic patients, those who received open-cell stents were four fold more likely to die or have a stroke or transient ischemic attack during the first 30 days, compared with patients who got closed-cell stents, Dr. Hart reported.

This difference in symptomatic patients was found to be statistically significant. However, a significant difference between the two stent designs was not seen in the asymptomatic patients.

Another analysis in the same patients looked at differences in 30-day outcomes relative to the type of embolic-protection device used.

The devices were divided into two types: those that are placed eccentrically in the distal carotid artery, and those placed concentrically. Eccentrically placed devices are believed to work better at trapping emboli.

The analysis showed that concentrically placed devices were associated with a threefold increased risk of adverse events, compared with those devices that require an eccentric placement in symptomatic patients; but this difference did not turn out to be statistically significant, according to Dr. Hart.

At the time of the meeting, two carotid stents were approved and were being marketed in the United States.

The Acculink carotid stent (Guidant Corporation), which was the first such model sold in the United States, has an open-cell design. The Xact stent (Abbot Vascular Devices) is a closed-cell model. Additional types of carotid stents are currently being sold in Europe, some of which have the open-cell design and others that have closed cells.