New studies have shown promising results with several innovative mesh-covered carotid stents. The findings suggest that the use of these devices may be associated with lower rates of early stroke compared with conventional carotid stents.

The two studies were published online December 10 in JACC: Cardiovascular Interventions.

The first reports on SCAFFOLD, a preliminary single-arm clinical study of the GORE Carotid Stent (WL Gore & Associates, Flagstaff, Arizona). The second is a meta-analysis of four trials involving two dual-layered mesh-covered stents, Roadsaver (Terumo Corp, Tokyo, Japan), and CGuard (InspireMD, Boston, Massachusetts).

Both articles report impressive 30-day stroke rates of 1.1% to 1.3%.

“I think we are seeing a new milestone with these mesh-coated stents in that we can achieve a very acceptable, low rate of complications and stroke even in high-risk patients,” the coauthor of an accompanying editorial, Harald Mudra, MD, Städtisches Klinikum, Munich, Germany, commented to Medscape Medical News. “If confirmed in larger and longer trials, these stents could open up a new population for carotid stenting who have previously been thought of as being too high risk for the procedure.

“We now only use these mesh-covered stents at our center,” he added. “I am convinced they are superior to conventional carotid stents. The extra layer of mesh keeps the small particles of plaque that can be released during the stenting process from entering the circulation.”

Asked how the stroke rate in these trials compared with those from other studies, Mudra said it is always difficult to compare stroke rates between trials, because the populations involved may be different, “but a 30-day stroke rate of around 1% after carotid stenting is a very low number, especially in the population involved in these studies, which were quite high risk with many elderly patients included.”

In these studies, stroke rates have been as low as or even lower than recent high-quality studies, such as CREST and ACT 1, which involved much lower-risk populations, Mudra noted.

However, he cautioned that the current studies are quite small and that longer follow-up in larger populations is needed to confirm these results.

The current articles explain that although recent trials that compared carotid artery stenting and carotid endarterectomy reported similar results regarding major outcomes (ie, death, stroke, and myocardial infarction [MI]) at 30 days, the rates of periprocedural minor stroke were higher in the patients who underwent stenting.

It has been suggested that a possible reason for this is that plaque protrudes through the stent, causing embolization.

Closed-cell stents provide more adequate plaque coverage and have been shown to be associated with a reduced risk for stroke compared with open-cell stents. However, closed-cell stents are less flexible, which makes correct placement difficult. A possible solution to the problem is the use of dual-layered mesh-covered stents, which offer both improved coverage and good flexibility, the researchers say.

SCAFFOLD Study

The SCAFFOLD study is the first US study to test the new Gore mesh-covered carotid stent. The authors describe these stents as having a smaller range of pore sizes, which allows for better coverage of the carotid plaque compared with existing open- and closed-cell stents.

The device consists of a self-expanding nitinol stent frame with a 500-mm pore size micromesh lattice on the exterior of the stent frame. It also has a heparin coating that is said to create a persistent antithrombogenic surface.

The trial involved 312 patients who were treated with the Gore mesh-covered stent; 94.6% of patients also received an embolic protection device (a distal filter). Symptomatic carotid stenosis was present in 15%, and the patients had a high degree of comorbidity. Anatomic high-risk criteria for surgery were present in 43% of the patients.

The primary analysis focused on the 265 patients who were determined by a screening committee to have no protocol violation (mainly anatomic exclusions). These patients constituted the per-protocol population. In this population, the 30-day rate of death, stroke, or MI was 3.0%, and the rate of stroke or death was 1.5%. The 30-day stroke rate was 1.1%. The two deaths that occurred were not stroke related.

Among all treated patients, 15 (4.8%) had experienced a major adverse event at 30 days. This composite included two deaths (0.6%), nine strokes (2.9%), and four MIs (1.3%).

Improved patient selection in the SCAFFOLD trial appears to have contributed to the difference in stroke rates between all treated patients (2.9%) and the per-protocol population (1.1%), the authors say. The low rate of stroke in the per-protocol population highlights the critical role of patient selection in carotid stenting, they add.

Commenting on this, Mudra said: “The analyses just focusing on the per-protocol population is not the most rigorous approach. That is not how trials should really be done. But I understand they had to try and compensate for investigators enrolling the wrong patients.

“And it does emphasize the importance of selecting the right patients for the procedure,” he added. “If the lesions are too calcified or too fragile or is in a difficult position to access, then it is not going to work as well. However, this can be quite subjective.”

The SCAFFOLD authors note that the mesh-covered stent is intended to provide additional protection against plaque protrusion and therefore reduce the incidence of late embolic stroke events. With this in mind, they point out that in this study, all stroke events occurred on the day of the procedure, with the exception of one hemorrhagic stroke, which occurred on day 6 and is more likely to have been a hyperperfusion event, given the timing.

“While the number of stroke events is too small in this study to make definitive statements, the lack of late stroke events is nevertheless supportive of the hypothesis,” they state.

The SCAFFOLD study investigators are continuing to collect follow-up data at 1, 2, and 3 years post procedure.

In his editorial, Mudra says the study shows that consequent use of a protection device, appropriate patient selection, and implantation of novel mesh-covered stents can reduce the 30-day stroke rate to 1.1%, which is lower than the rates observed in both the stenting and the surgery groups in the large randomized trials, despite higher patient comorbidity. However, the long-term outcomes with the GORE Carotid Stent have yet to be analyzed.

Meta-analysis of Four Trials

The second article in the same issue reports a patient-level meta-analysis of four trials with two different dual-layered mesh-covered stent models: two trials with Roadsaver (Terumo Corp, Tokyo, Japan), and two trials with CGuard (InspireMD, Boston, Massachusetts). The trials included a total of 556 patients.

The patient characteristics were similar to those in the SCAFFOLD trial, with a slightly higher rate of symptomatic stenosis (17.3%) and a slightly lower rate of use of an embolic protection device (92.4%).

Results showed a 30-day composite rate of stroke or death of 1.4%. There were six periprocedural strokes (1.08%), all of which were minor. During 30-day follow-up, there was one death (0.17%) from MI and one additional minor stroke (0.17%).

The cumulative 30-day mortality rate was 0.17%; the incidence of stroke at 30 days was 1.25%.

Mudra summarizes that “both reports show the use of mesh covered stents to be very safe.”

He adds: “Up to now, there is no evidence for a higher rate of stent thrombosis with mesh-covered stents, but a note of caution remains with respect to a potential higher restenosis rate.

“Due to their small pore sizes, treatment of unstable plaques in high-risk lesions is a potential target for this stent type, widening the indication for carotid stenting,” he concludes.

Large randomized trials with longer follow-up comparing mesh-covered stents with surgery and/or conventional stents are urgently needed, and if such trials can confirm the results of the current studies, this novel stent technology will represent a new milestone in carotid stenting, he states.