Invited commentary

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According to the study results, Dr Bozier’s group claimed that closed cell stents and concentric embolic protection devices are associated with fewer neurologic events in symptomatic patients and in patients who have echolucent plaques. Coming from an experienced group with a large cohort of patients in whom the preoperative and postoperative symptoms were assessed by an independent neurologist, these conclusions deserve consideration. According to Houdart (P. Houdart, Lariboisiere Hospital, Paris; personal communication), the average free surface between the struts of the stents is around 5 mm², with ranges from 1.08 mm² for the carotid Wallstent to 11. 48 mm² for the Acculink stent. At first sight, it seems logical that stents which have the smallest free surface are those which are the more able to prevent particles and debris from drifting into the brain. Furthermore, with large open cells, some struts may even protrude into the lumen of the artery. In one of our recent cases, the wire of the filter was blocked by the floating strut, thus preventing the retrieval of the system.

The current study, however, has some weaknesses which, in my view, make Dr Bozier’s group’s conclusions still debatable.

Stent free surface is not the only factor of reliability of carotid stents. Mechanical properties including flexibility and radial forces are as important. In tortuous arteries, as well as in cases of wide discrepancies between the common and the internal carotid arteries, the greater the flexibility, the better the conformability. In these difficult situations, more flexible open or semiopen stents may offer a better option. Thus, a compromise between small cell area and vessel wall conformability represents the ideal stent.

In summary, the main merit of this study is to remind physicians that stent and cerebral protection devices (CPD) designs may play a role in the results of carotid artery stenting (CAS). We agree with Dr Bozier’s statement that further well designed comparative prospective studies are needed to explore this role. These evaluations should be put in the context of the two recently completed randomized studies comparing CAS and carotid endarterectomy (CEA) which showed no advantages of CAS over surgery.