Surmounting Minor Stroke: New Devices, TCAR Aim to Cut Risk of Carotid Artery Stenting

HOLLYWOOD, FL—Carotid artery stenting (CAS) and endarterectomy (CEA) remain neck and neck in vying for prominence, but some experts say a minimally invasive surgical approach known as transcarotid artery revascularization (TCAR), as well as new filters and devices that aim to cut the risk of minor stroke with stenting, could well shift the balance away from surgery.

Moreover, still-pending results from the CREST-2 trial will clarify the position of medical therapy compared with revascularization.

“We were running a little bit behind milestones, and I think right now we’re about right at milestones in terms of achieving the actual enrollment,” Barry T. Katzen, MD (Miami Cardiac & Vascular Institute, FL), reported at the 2019 International Symposium on Endovascular Therapy (ISET). “So this trial is moving along quite well, just slightly below the projected accrual rate. Interestingly enough, endarterectomy was lagging behind stenting in terms of accrual, but now it’s pretty much 50-50, which is great news for the ultimate statistical analysis of this trial.”

As of March 31, 2018, CREST-2 had enrolled 986 patients in the randomized portion of the trial. According to the trial’s website, 1,291 out of 2,480 participants have now been enrolled.

CREST-2 is looking into how revascularization fares against rigorously controlled medical therapy alone in asymptomatic patients, with an unusual, two-arm design that will likely preclude direct comparisons between stenting and surgery. Its primary endpoint is any stroke or death within 44 days of randomization or ipsilateral ischemic stroke thereafter up to 4 years.

But the CREST-2 registry is also important for stenting practitioners, Katzen added, in that it enables operators to gain necessary skills required to earn the blessing of the US Centers for Medicare & Medicaid Services. “The rationale behind the registry is to develop enough carotid stenters to be actually able to safely randomize, so that we’re not comparing inexperience to experience as an external factor,” Katzen explained, adding that the focus here is on high-risk patients, though some treatment of low-risk patients is allowed.

“So is CREST-2 going to be the final answer? I’m not sure we’ll ever get a final answer in healthcare, but we’re very excited about CREST-2 approaching the conclusion of the trial,” he said. “And we’re very hopeful it is going to find us the answers we need about the role of medical therapy, carotid stenting, and surgery—again, just remember this isn’t a stenting versus surgery trial but a medical therapy versus revascularization trial.”

CAS ‘From Good to Great’

In that same ISET session, William A. Gray, MD (Lankenau Heart Institute, Wynnewood, PA), reflected on what technologies are set to move CAS “from good to great,” specifically as it pertains to reducing stroke risk.

The original CREST trial showed no difference in the primary endpoint (any stroke, MI, or death during the periprocedural period and ipsilateral stroke thereafter) out to 4 years, Gray pointed out. ACT I additionally showed no difference between CAS and CEA out to 5 years.

Minor stroke, though, occurred at nearly twice the rate with stenting compared with surgery in CREST, Gray said. Consistent results were seen in ACT I. “Take heart, most of those minor strokes resulted in no permanent deficit, but it’s still a mechanistic issue we need to address,” he added.

As to how technology can help, Gray highlighted the Paladin and Neuroguard embolic protection devices (both Contego Medical). The next-generation Neuroguard “is going to be an all-in-one system, so that there will be a stent on the balloon with the filter . . . . [It’s] a 5-minute procedure. Most of the mischief we get into with carotid stenting has to do with operator error, so this is a real advancement I think.”

Plaque prolapse, which “might be a provocateur of late stroke” after the intervention, is another area for improvement in CAS, Gray continued. Mesh stents such as CGuard (InspireMD), Roadsaver (Terumo), and Gore (WL Gore) have various features such as small pore sizes or layers of woven netting that provide better coverage, he explained.

The Gore stent has shown better performance in terms of clinical outcomes and surrogate markers, specifically in the SCAFFOLD study, than earlier devices, Gray noted. So, too, has TCAR, he added.

TCAR: A Different Take on CAS

Centering his presentation on TCAR, Marc Schermerhorn, MD (Beth Israel Deaconess Medical Center, Boston, MA), described an alternative form of carotid revascularization.

In this procedure, the catheter is inserted directly into the carotid artery through a small incision just above the patients’ clavicle. TCAR involves CAS along with a neuroprotection system, collectively called Enroute (Silk Road Medical), that temporarily reverses blood flow in the carotid artery to divert emboli away from the brain.

“TCAR represents a totally different way for approaching things,” and the 30-day stroke rate of 1.4% seen with the procedure in the ROADSTER study is one the lowest ever reported by a clinical trial of carotid stenting, Schermerhorn said. The method avoids the aortic arch and doesn’t require crossing the lesion to get embolic protection.

“But there have been limited data outside of the highly selected patients and providers in the ROADSTER study,” he noted, “so it leads to a question about generalizability: can we get those results more broadly?”

To flesh out the evidence base, the Society for Vascular Surgery’s VQI TransCarotid Revascularization Surveillance Project (VQI-TCAR) began in September 2016 and is comparing outcomes of TCAR enrolled in the study versus those of contemporaneous CEA cases. Analysis of the data through December 2018 shows similar death and stroke rates for the two procedures. With TCAR, though, mean operative time was shorter (75 vs 115 min) and the risk of cranial nerve injury was a relative 90% lower compared with CEA no matter whether patients were symptomatic or asymptomatic (P < 0.001 for all).

“From my perspective,” Schermerhorn said, “things that have a lesser impact on overall quality of life like cranial nerve injury become more important when you don’t have to accept a higher rate of stroke.” One-year follow-up data from VQI-TCAR will be reported soon, he concluded.

Asked by Katzen how he selects patients for TCAR, Schermerhorn replied that he focuses on patients at high risk for CEA. The main requirement, he added, is that the distance between the clavicle and the bifurcation must measure at least 5 cm. Other less common reasons for not pursuing TCAR are plaque at the common carotid puncture site or bifurcation anatomy that isn’t suitable for carotid stenting. Schermerhorn says he reserves transfemoral CAS for use in patients who aren’t TCAR candidates but for whom CEA is too risky.

“There are many vascular surgeons who have not necessarily been advocates for stenting, in fact may have been skeptical about stenting [but] now frequently are embracing this because of convenience and compensation. For the hospitals it’s a wash either way,” Katzen observed. “What are your thoughts about what’s driving this? Because I think for many of us [the treatment decision is] still an issue of who’s high risk. Is carotid endarterectomy still the gold standard, for instance?”

Surgery still comes out ahead for now, Schermerhorn commented, though TCAR is emerging as an alternative and the new technologies will continue to improve transfemoral CAS.