Effects of Cerebral Protection With Filters vs. Flow Reversal on Cerebral Embolization After Carotid Artery Stenting

Overview

Carotid artery stenting (CAS) with cerebral embolic protection is the preferred treatment for narrowing of the carotid arteries in patients at high risk for open surgery. Special devices are used to protect the brain from particles(emboli) that may break off when the narrowing or blockage is cleared during the angioplasty and stenting procedure. Although filters are most frequently used, protection systems consisting of balloons and flow reversal are also available for cerebral embolic protection. However, there is little information about the effectiveness of filters compared with balloons and flow reversal for prevention of embolization during CAS. The aim of our study is to address this major problem. Our study was designed to answer two specific questions: First, the study will investigate whether balloon-based protection systems are more effective than filters in reducing the amount of particles that break off and travel to the brain during CAS. For this purpose two imaging techniques will be used: magnetic resonance imaging of the brain (MRI), and transcranial doppler (detection of microparticles in the small brain vessels using ultrasound). Second, it will be investigated whether the use of balloon-based protection devices are more effective than filters for prevention of stroke, heart attacks, and death after carotid stenting. The results of the study will provide important information to find out the best way to protect the brain from plaque fragments that may break off during CAS.

Description of Procedures to be performed Pre-Procedure Medication Regimen The standard of care premedication with antiplatelet therapy for CAS will be used for the study. To minimize the risk of neurological events related to stent thrombosis during the procedure, subjects should be provided antiplatelet therapy for a minimum of 48 to 72 hours prior to the procedure, to include: 1) Aspirin 325 mg daily and 2) Clopidogrel (Plavix®) 75 mg twice daily OR Ticlopidine (Ticlid®) 250 mg twice daily A protracted dose of premedication may be substituted by administering a loading dose of antiplatelet therapy at least 4 hours prior to the carotid intervention on the day of the procedure, to include: 1) Aspirin A 650 mg loading dose of aspirin, provided that it is not enteric coated or extended release, and 2) Clopidogrel (Plavix ®) 450 mg. Procedure: Patients will undergo CAS with FDA-approved carotid stents under embolic protection with the Accunet device or the Gore NPS. All CAS procedures will be performed through retrograde access from the common femoral artery. CAS procedures will be performed using a fixed angiographic unit (Allura Xper FD20, Philips, Bothell, WA). Procedural details and CAS protocols will follow techniques described in detail before.14 The procedure will be performed under local anesthesia with minimal sedation to facilitate continuous neurological evaluation. Baseline angiographic studies will be performed concurrently with the CAS procedure. The diagnostic angiography will be reviewed to ensure that the patient does not meet any applicable angiographic exclusion criteria. Once this has been determined, randomization will be performed. The Accunet filter or the Gore NPS will be used according to the instructions for use. Ultrasound-guided access to the ipsilateral or contralateral femoral vein will be obtained if the patient is randomized to CAS with the Gore NPS. Neurological monitoring of the subject's level of awareness will be evaluated every 5 to 10 minutes during the CAS procedure. Patients deemed ineligible by angiographic criteria will be considered screen failures and will be excluded from the study. These patients may receive further treatment outside of the study protocol according to usual practice and standard of care. Transcranial Doppler Protocol: Transcranial Doppler signals, using a portable digital 2-MHz PMD/spectral TCD unit (PMD150, Spencer Technologies, Seattle, WA), will be recorded from bilateral middle cerebral arteries via transtemporal windows. Monitoring will be started in the operative room immediately before CAS and continued until the end of the case or for at least 15 minutes after removal of the neuroprotection system. A head frame will be used for ultrasound probe fixation and continuous flow assessment in M1 segment of the middle cerebral artery (MCA). Several TCD parameters will be recorded: MES counts and microemboli shower detection during the different steps of the procedure, initial MCA mean velocity, mean MCA velocity during CAS, and final mean MCA velocity. MES will be identified according to the recommended guidelines.31 Data will be stored on a hard disk using a coding system and will be analyzed off-line on a later day by readers who will be blinded to patient information. Diffusion-weighted MRI exams: All patients will have DW-MRI scans of the brain obtained within 24 hours prior to CAS and 18 to 24 hours after CAS. Postprocedural DW-MRI studies will be compared to preprocedural studies to identify new procedure-related ischemic cerebral lesions.32, 33 DW-MRI will be obtained using standard head coils on 1.5 Tesla Siemens scanners (Siemens Avanto or Magnetom Sonata, Siemens, Erlangen, Germany). DW-MRI with echo-planar imaging sequence (B0 = 1000) and fluid-attenuated inversion recovery (FLAIR) images will be obtained in axial and coronal sections. The DW-MRI studies will then be evaluated by neuroradiologists blinded to the clinical status, the type of embolic protection and TCD data of the patients. On the postprocedural MRI, acute embolic lesions will be defined as focal hyperintense areas with restricted diffusion signal, which will be confirmed by apparent diffusion coefficient mapping to rule out artifacts. New postprocedural cerebral lesions consistent with microemboli will be recorded in terms of location and number for all DW-MRI exams performed.