Proximal Protection During Carotid Stenting Reduces Silent Infarcts

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Proximal protection with flow reversal during carotid artery stenting (CAS) reduces new ischemic cerebral lesions compared with distal filter protection, according to a small single-center study published online September 7, 2012, ahead of print in the Journal of Vascular Surgery.

Researchers led by Ignacio Leal, MD, of Hospital Virgen de la Salud (Toledo, Spain), looked at 2 groups of consecutive patients with carotid atherosclerosis at high risk for endarterectomy. The first group (n = 31) received transcervical CAS with flow reversal for cerebral protection, while the second group (n = 33) received transfemoral CAS with distal filter protection.

With flow reversal, antegrade blood flow from the common carotid artery and retrograde blood flow from the external carotid artery are halted, after which the suspended blood is aspirated, along with any particles, to protect the brain from emboli.

In the study, all procedures were performed by vascular surgeons experienced with CAS. Baseline characteristics were similar between groups, including presentation with symptomatic disease (stroke or TIA; 70% in each group).

All procedures were technically successful without residual stenosis and with similar mean surgical times (46 minutes in the flow reversal group vs. 52 minutes in the filter group; P = 0.324). On postprocedural diffusion-weighted MRI (DW-MRI), more new cerebral ischemic white matter lesions were found in the filter group, with most being located ipsilaterally (table 1).

Table 1. Postprocedural Ischemic Cerebral Lesions After CAS on DW-MRI

All white matter lesions were asymptomatic, and the Rankin stroke scale did not deteriorate in any patient.

After adjustment, age (RR 1.022 95% CI 1.021-1.042; P < 0.001), recent symptomatic status (RR 4.109; 95% CI 1.74-9.65; P < 0.001), and closed cell vs. open cell stent type (RR 0.082; 95% CI 0.019-0.359; P < 0.001) were independent predictors of embolization in the distal filter group, but not the flow reversal group.

Over a mean follow-up of 23.25 months, there were no new neurologic events, deaths, or admissions to the hospital. The Rankin stroke scale remained unchanged in all patients and according to ultrasound, all stents remained patent with no signs of restenosis.

“Our data strongly suggest that transcervical carotid stenting with carotid flow reversal may produce a significantly lower incidence of cerebral embolization compared with conventional transfemoral carotid stenting procedures with distal filter protection,” the authors conclude.

Distal Filters Problematic

They note that current distal filters can encounter a number of issues, including “internal carotid artery spasm, increased crossing profile for the initial wire access, and technical misadventures in attempts to retrieve the filter after stent deployment.” Moreover, the current generation of commercially available filters feature pore sizes of 100 µm to 150 µm, while microemboli less than 60 µm have been shown in experimental models at all stages of the procedure, including initial wire passage.

In a telephone interview with TCTMD, Christopher J. White, MD, of the Ochsner Heart and Vascular Institute (New Orleans, LA), agreed that distal filters can be problematic. “With a filter, by definition there’s flow through the filter, and particles smaller than the size of the filter get through, so no one should expect that a filter will stop everything,” he said. “With flow reversal, there’s no forward flow, so it will stop everything.”

Dr. White pointed out that while the 2 patient groups in the study underwent CAS by alternate access routes (cervical vs. femoral), the different cerebral protection devices was the key. “I don’t think the transcervical aspect is important,” he said. “This is good confirmatory evidence supporting proximal protection over filters and as part of several other trials, it seems like this is the real deal.”

No Infarct Better Than Any Infarct

Dr. White noted that proximal protection (performed during transfemoral CAS) is currently preferred over filter devices at his institution. Nevertheless, while many believe flow reversal is more effective at stopping periprocedural embolic debris, the clinical consequences of such silent cerebral lesions are unknown. “The clinical impact of these is uncertain—nobody knows what they mean,” he acknowledged. “But everyone agrees it would be better if they weren’t there. We all agree they are related to the procedure and they probably represent micro-infarcts, and no infarct is better than any infarct at all.”

In terms of the patients at highest risk of microemboli during CAS, Dr. White indicated they include the elderly with large, bulky plaque. “They’re at very high risk of embolic material and are the best candidates for proximal protection,” he said.

In the paper, the authors note that “the existence of worse prognostic data in older patients, symptomatic patients, and CAS with open-cell stents only in the transfemoral group could be critical subgroups that benefit most from the use of. . . flow reversal.”

Currently, approved flow reversal systems in the United States include the MO.MA device (Medtronic/Invatec, Minneapolis, MN) and the Gore flow reversal system (W.L. Gore, Flagstaff, AZ).

Study Details

Carotid Wallstents (Boston Scientific, Natick, MA) or Protégé Rx (ev3 Endovascular, Minneapolis, MN) stents were used for CAS procedures, as were self-expanding Filter Wire EZ (Boston Scientific) devices in the filter group. The authors achieved flow reversal by first cannulating the common carotid artery (CCA) and internal jugular vein with 8-Fr introducers and then connecting them with tubing to allow arteriovenous flow. A Rummel loop is then placed around the CCA to interrupt flow during the procedure.

Source:

Leal I, Orgaz A, Flores A, et al. A diffusion-weighted magnetic resonance imaging-based study of transcervical carotid stenting with flow reversal vs. transfemoral filter protection. J Vasc Surg. 2012;Epub ahead of print.

Disclosures:

• Dr. Leal reports no relevant conflicts of interest.
• Dr. White reports serving as the national principal investigator of the CABANA trial, which evaluated a filter device and was sponsored by Boston Scientific.

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