Conference Coverage

Hybrid carotid stents eyed with cautious optimism


 

EXPERT ANALYSIS FROM THE NORTHWESTERN VASCULAR SYMPOSIUM

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CHICAGO – The next generation of hybrid carotid stents is slowly breathing life into the stagnant field of carotid artery stenting.

The new hybrid stents combine the flexibility of a traditional open-cell, nitinol stent with the stabilization typically offered by a closed-cell stent design. The initial clinical experience is limited, but shows promising results against embolization, Dr. Claudio Schönholz said at a symposium on vascular surgery sponsored by Northwestern University.

Last year, Dr. Schönholz and his colleagues at the Medical University of South Carolina in Charleston reported the first-in-man use of the investigational Gore Carotid Stent (W.L. Gore & Associates) (J. Endovasc. Thera. 2014 Aug;21:601-4).

As part of the Gore Carotid Stent Clinical Study for the Treatment of Carotid Artery Stenosis in Patients at Increased Risk for Adverse Events from Carotid Endarterectomy (SCAFFOLD) study, the team has successfully treated another four patients with no evidence of peri- or postprocedural neurological events. This included a case with such severe high-grade stenosis and slow flow that the external carotid artery was not even visible on imaging before the stent was placed, Dr. Schönholz said.

The Food and Drug Administration recently reviewed unreleased data for the first 100 patients enrolled in SCAFFOLD and given the green light for the multicenter, 312-patient study to resume with the start of the new year, he said.

Medtronic’s Cristallo Ideale hybrid stent is already approved outside the United States and was associated with no major neurological events and two cases of transient ischemic attack in 124 patients treated at four expert centers in Italy and Germany in the Cristallo study (J. Endovasc. Ther. 2008;15:186-92).

A more recent retrospective study revealed only one minor stroke in the perioperative period and during the first 30 days in 68 patients with symptomatic carotid stenosis treated by Turkish surgeons with the Cristallo Ideale stent and a proximal protection device (MO.MA, Invatec s.r.l., Medtronic, Italy) (Int. Angiol. 2014 Nov. 14. [Epub ahead of print]).

Better patient selection, increased operator experience, and use of embolic protection devices has reduced neurological events associated with carotid artery stenting, but embolization still occurs after protection devices are removed due to plaque protrusion through the stent struts, Dr. Schönholz said.

The unique design of the hybrid stents “may prevent plaque protrusion, eliminating peri- and postprocedural events,” he said.

The Cristallo Ideale hybrid stent is a nitinol-based stent that has a closed-cell portion at its center and an open-cell configuration on the distal and proximal sections.

In contrast, the Gore Carotid Stent has a closed-cell component throughout the entire device length that is created by placing an expanded polytetrafluoroethylene lattice with 500-micron pores over an open-cell frame. Once combined, both the stent frame and lattice are coated on all surfaces with Carmeda Bioactive Surface (CBAS) heparin. It’s action is limited only to the device surface and has no systemic anticoagulation effects, said Dr. Schönholz, who disclosed serving on Gore’s scientific advisory board.

The open-cell frame allows a high degree of flexibility and conformity to the native anatomy, while the stent lattice provides a high degree of plaque scaffolding that can reduce plaque prolapse, he said. The lattice also reduces the amount of emboli released during and after stent deployment and stabilizes the stent frame by resisting elongation as well as “fish-scaling,” or the misalignment of stent struts that protrude into the vessel wall, particularly when stents are deployed in tortuous anatomy.

When asked during a discussion whether the same results couldn’t be achieved by simply putting in another covered stent like a Viabahn, Dr. Schönholz replied that the Gore Stent isn’t a true covered stent because the 500-micron pores allow perfusion to be maintained to the external carotid artery. “It was intended to prevent plaque profusion, but at the same time allowing perfusion of the external carotid,” he said.

So far, the investigators have not incorporated intravascular ultrasound during stent placement, as it was not part of the SCAFFOLD protocol, but this will likely be used once the device is approved, he added.

Course director Dr. Mark K. Eskandari, chief of vascular surgery at Northwestern University in Chicago, said the results show that “carotid stenting isn’t dead yet and we can persevere. Advances in technology, both in regards to mechanical embolic protection devices and stent design systems, continue to improve the already great results of carotid artery stenting.”

pwendling@frontlinemedcom.com

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