More questions asked of carotid artery stenting

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At the 14th International Workshop on Endovascular Therapy, Ajaccio, Corsica, endovascular specialists from around the world gathered to analyze and debate the latest developments, therapies, materials and techniques, as well as the indications for intervention. As ever, the International Workshop tackled the most controversial issues and the highlight this year’s programme organised Dr Jos van den Berg under the direction of Drs Lucien Castellani, Geoffrey Gilling-Smith and Torben Schroeder, was a fascinating session on carotid stenting that highlighted many key questions regarding the future of carotid stenting.

The session assessed stent design, the importance of medical therapy in future trials, the significance of plaque type as well as the degree of stenoses and a discussion on the ‘Achilles Heel’ of carotid stenting – the aortic arch.

The session began with a review of carotid stenting trials and examined in detail the reasons for the different results in different trials. Dr Clement Darling, Albany, USA, said that although there is much data available most of which is from many different sources and therefore there is a disparity of results from multi-centre trials to single centres, industry non-industry sponsored registries. He added that there were few registries that provide ‘real world’ data as they are limited by a lack of objective monitoring, patient selection bias, lack of strong follow-up, minimal risk factor stratification, voluntary self reported data and variable endpoints.

Robin Williams, Newcastle, UK, examined several carotid stenting trials (SAPHIRE, SPACE, EVA-3S and ICSS) and commented that although three of the trials (SAPHIRE, SPACE, and EVA-3S) were stopped early they did provide some significant insights. Most importantly, they highlighted the long and flat learning curve for operators (which Williams placed at 50-100 cases), issues of conflicts of interest and the absence of consensus especially in defining what constitutes a ‘high-risk’ patient. He concluded that current trials such as ICSS and CREST must be allowed to run to their conclusions.

In a commentary, Ross Naylor, Leicester, UK, said that the design and methodology of carotid stenting trials needs re-examining, and asked delegates to consider what is ‘high-risk’ and is a ‘high-risk’ patient one who will benefit the most from carotid stenting. He added that there is no compelling evidence that the asymptomatic patients in trials (SAPPHIRE) or registries are ‘high-risk’ for stroke and that there continues to be a discrepancy between what is happening in trials and registries, and in the ‘real world’.Access, stent design and EPDs

The issue of access was then discussed by Patrice Bergeron, Marseille, France, who reminded delegates that aortic and carotid anatomy dictates only the technical approach to intervention, and not the indication. He added that it was very important to be selective and respect the contraindications for carotid stenting: highly calcified lesions, floating thrombus, arch difficulties or carotid tortuosity or difficult arch anatomy. Bergeron said he preferred the femoral approach as brachial access demands a high level of expertise. Occasionally, he utilised cervical access, but this was normally in difficult arch anatomy with patients over 70-80 years of age and severe CCA tortuosity.

Dr Mark Wholey, Pittsburgh, USA, then discused stent design. He began by stating that the purpose of a stent is to support the plaque against the vessel wall, optimise scaffolding, allow angiographic outcome, prevents recoil and will not fracture over time. Regarding the debate between open vs. close cell configuration, he said that it was the size of the cell that was of crucial importance. However, he noted that pore size will always be much larger that the size of embolic particles, which are approximately 100 microns whereas the smallest cells are 600 microns. Wholey went on the outline that there are some 20 factors that affect outcome and stent design is only one, adding “the literature doesn’t seem to care which one.”

Wholey stated that in his mind one of the most important aspects surrounding carotid stenting was the aortic arch, its ‘Achillles Heel’. One interesting concept was the ‘covered stent’, although Wholey acknowledged that it can block the external carotid artery.

Following Wholey, Dr Carlo Setacci, Italy, discussed the use of embolic protection devices (EPD) and the different systems available such as distal filters, proximal filters and the flow reversal concept. Interestingly, he cited data from the BIC (Belgium-Italian) registry that reported no significant difference in outcomes between EPDs. He concluded that the use and selection of an EPD required a differentiated strategy and depended on anatomy, although recommended using the distal filter in standard cases. Again, Peeters re-iterated his thoughts and added that current EPDs are good, it is the stent design that is inadequate and a new concept of stent design was needed.

Discussion

The session finished with a frank and revealing discussion, including an overview of carotid stent usage in West Europe and North America. Drs Ted Diethrich, Pheonix, USA, and Wholey stated that in the US (due to the recent decision by the CMS not to expand reimbursement) stenting is only allowed if part of an Investigation Device Exception (IDE) clinical trial. In Europe there is a similar situation, with Drs Pascal (France), Malina (Sweden) and Naylor all stating that carotid stenting was utilized in their countries primarily within a clinical trial.

Elsewhere in Europe, Professor Peeters (Belgium) informed delegates that there was no reimbursement following a Health and Technology Assessment report that concluded there was no evidence in favor of carotid stenting, and this would not change unless it could be proved stenting was superior to surgery. Professor Jan Brunkwall (Germany) stated that there was no reimbursement in Germany with approximately 5-10% carotid stenting penetration, which was mostly performed by cardiologists. For Denmark, stenting penetration was also very low with only symptomatic patients considered ‘high-risk’ for surgery receiving stents.

Interestingly, there was opposition to so-called ‘un-audited’ registries and suggestions that many of the data from randomised controlled trials were now obsolete, as there had been a dramatic improvement in medical therapy. This in turn led to calls for by both Frank Veith (New York) and Naylor for the Transatlantic Asymptomatic Carotid Intervention Trial (TACIT) and ACST-2 to possibly unite and include a medical therapy arm as well as carotid surgery and stenting arms. Diethrich asked whether the reluctance to include a medical therapy arm was because there is a real worry that medical therapy could win?

The discussion then moved towards plaque and the degree of stenosis. Both Giorgio Biasi (Milan, Italy) and Diethrich agreed that although the degree of stenosis was important, further investigation into plaque type was warranted. Wholey agreed and stated that at his center Intravascular ultrasound (IVUS) is performed on each patient. Indeed, the Carotid Artery Plaque Intravascular ulTrasound evALuation (CAPITAL) study may go someway to providing some much needed answers. The aim of this study is to assess the safety and feasibility of Volcano Corp Eagle Eye Gold Catheter system to correlate the presence and characteristic of carotid artery atherosclerotic disease with anatomic and histologic analysis.

The audience discussion at the Ajaccio Workshop highlighted that both registries and randomised controlled trials were either biased or flawed in their design, and that any new trials should incorporate a medical therapy arm. There were also calls for some form of consensus on the definition of ‘high-risk’ from surgery, renewed calls for new stent designs and further analysis of plaque type. In conclusion, it can be stated that carotid artery stenting although seemingly safe and feasible, has not yet achieved the same outcome (non-inferior) as carotid surgery.