Is current carotid stent design inadequate?


At CX33, there was a debate on the motion “Current carotid stent design is inadequate and contributes significantly to procedure-related stroke.” Sumaira Macdonald, Newcastle, UK, spoke for the motion and William Gray, New York, USA, against.

Macdonald stated that there remained an excess of minor strokes associated with stenting compared to endarterectomy, which is a consistent finding in almost every randomised trial seeking to compare the two interventions. “I believe that there is room for further improvement of stenting and stent design can and does impact on outcome. Attention to this fact will lead to further reductions in procedural risk,” she said.


“Why should stent design not impact on outcome? Individual arterial territories demand individualised solutions. The inexorable drive to improve aortic stent graft parameters is intended to improve outcomes with respect to length of stay and late interventions to better secure aneurysm exclusion from the circulation. The superficial femoral artery, a traditionally hostile territory for stent placement resulting from unique haemodynamics, has benefited from advances in stent design. The carotid bifurcation lesion presents a particular endovascular challenge, requiring that a stent couples conformability with scaffolding sufficient to ‘brace back’ friable plaque,” she said.


Macdonald told delegates when data conflict, there is bound to be a difference in opinion. The key is the definition of those populations in whom stent design is a crucial consideration and those in whom it is of secondary relevance.


She pointed to the overall event rates for stenting falling to 2.7% or 2.9% (all stroke/death) in independently reviewed registries with independent adjudication of events (ARMOUR, EMPiRE CAS registries evaluating the proximal embolic protection systems the Medtronic/Invatec Mo.Ma and the Gore flow reversal systems respectively), but noted that it was a statistical challenge to derive any meaningful difference in outcome between open-cell and closed-cell carotid stents unless several thousand patient outcomes can be compared.


Macdonald told delegates that the use of surrogate markers of stroke and death allows for a more convenient comparison of outcomes which can be stratified by stent design. “New hyperintensities on diffusion weighted MRI of brain and microembolic signals on transcranial Doppler following stenting are florid by comparison with stroke and death. However, though there are differences in these parameters based on stent design, an important limitation is that these surrogates may be dismissed as clinically dubious or irrelevant,” Macdonald said.


Speaking against the motion, Gray said, “The stent is only one of several other very plausible causes of stroke in carotid artery stenting. If only ~20% of all strokes related to stenting are plausibly related to the stent, then the stent cannot be significantly implicated in stroke generation.”


Gray noted that at-risk plaques (patients with recent symptoms and patients over the age of 80) do not exhibit higher “stent-related” stroke. “Stent minimum cell unsupported area does not significantly differ among stents,” he said.


Gray also noted that pharmacology of stenting demonstrates a greater correlation with outcomes than does stent type. He told delegates: “As an example, there is an increasing age-related resistance to clopidogrel that correlates with age-related carotid artery stenting outcomes.”


Speaking on the data available, Gray said that the well-controlled prospective, non-selection biased data demonstrated no differences by stent types.