Safety of Protected Carotid Artery Stenting in Patients with Severe Carotid Artery Stenosis and Carotid Intraplaque Hemorrhage

Study Population

From a prospective registry of 91 consecutive patients who were treated with elective CAS and distal embolic protection, we selected 80 patients who underwent neck 3D TOF MRA within 1 month before CAS. Two patients whose neck MRA was of insufficient quality for reliable evaluation were excluded, leaving 78 patients in the study. This study was a retrospective analysis approved by our institutional review board. Informed consent for the retrospective analysis of the patient data was waived by the institutional review board.

According to previously published criteria,¹⁴ all 78 patients undergoing protected CAS are at high surgical risk for carotid endarterectomy. The high-risk features included were high cervical carotid stenosis (n = 38), clinically significant cardiac disease (n = 12), contralateral carotid occlusion (n = 10), age ≥80 years (n = 8), tandem stenosis ≥70% (n = 6), and severe pulmonary disease (n = 4). All patients had severe carotid stenosis (70% to 99%, based on NASCET criteria) on conventional angiography.

To evaluate baseline characteristics of the patients, the risk factors considered were defined as follows: history of ischemic heart disease was defined as a previous MI or coronary artery bypass grafting; dyslipidemia was defined as hypercholesterolemia (total cholesterol >220 mg/dL, low-attenuation lipoprotein >160 mg/dL, triglyceride >150 mg/dL, or high-attenuation lipoprotein <40 mg/dL) or treatment with cholesterol-lowering medication; hypertension was defined as systolic blood pressure >140 mm Hg and/or a diastolic blood pressure >90 mm Hg, or treatment with antihypertensive medication; diabetes mellitus was defined as a fasting serum glucose level >110 mg/dL, HbA1c >6.5%, or use of antidiabetic medication.

Symptomatic carotid artery stenosis was defined as the onset of focal neurologic symptoms (TIA or nonfatal stroke) occurring within 6 months of CAS and attributable to an ipsilateral carotid artery vascular distribution.

Carotid Stent Placement Procedure

Between August 2006 and June 2010, 91 consecutive patients with severe carotid stenosis and high-risk features were treated with protected CAS at our institution. The CAS procedures were performed by 1 interventional neuroradiologist with 10 years' experience in neurovascular intervention (W.Y.). Written informed consent for the CAS procedure was obtained from all patients. All patients were examined by a stroke neurologist before and after the procedure to document cerebrovascular symptom status and to record any new neurologic deficits. All patients were treated with aspirin at a dose of 100 mg/day and clopidogrel at a dose of 75 mg/day for at least 3 days before the procedure. At the beginning of the procedure, heparin was given intravenously as a 3000 IU bolus. All patients received aspirin and clopidogrel for at least 3 months after CAS.

All procedures were performed using a femoral approach. After placement of the 8F guiding catheter, diagnostic common carotid angiography was performed to determine the severity of carotid stenosis according to NASCET criteria. CAS was performed with the SpiderRX distal embolic protection system (ev3, Plymouth, Minnesota). After crossing the lesion with a microguidewire, the filter was deployed before predilation was performed. Predilation was performed with a 5- or 6-mm balloon catheter. CAS was completed using a RX Acculink carotid stent (Abbott Vascular, Santa Clara, California). Postdilation was not routinely performed. After CAS was completed, the filter was captured and retrieved by the delivery catheter, followed by completion of the angiography. Procedural success was defined as completion angiography showing <30% residual stenosis, without alteration in the intracranial circulation. After the procedure, all patients were monitored in the intensive care unit for 24 hours.

MR Imaging Examinations and Image Analysis

MR imaging examinations were performed on a 1.5 MR imaging scanner (Signa HDxt; GE Healthcare, Milwaukee, Wisconsin) using an 8-channel phased-array coil, and included routine clinical brain MR imaging sequences, 3D TOF MRA of the circle of Willis, and neck 3D TOF MRA. The indications for MR imaging examinations were TIA or ischemic stroke (n = 40), headache (n = 22), routine medical work-up (n = 14), and amaurosis fugax (n = 2). The mean period between MR imaging and CAS was 16 days, ranging from 1–30 days.

The neck 3D TOF MRA was acquired with a multiple overlapping thin-slab acquisition in the axial plane using a gradient-echo technique with the following parameters: TR/TE/flip angle, 24 ms/6.8 ms/20°; FOV, 240 × 240 mm²; matrix, 384 × 160; section thickness, 2 mm; 65 sections. The acquired voxel size was 0.63 × 1.5 × 2 mm³ and was reconstructed to a matrix of 512 × 512, with interpolation to 132 sections at 1 mm. The total coverage was 130 mm, and the scan time was 2 minutes 15 seconds.

Two neuroradiologists reviewed the TOF source images of the carotid bifurcation and the proximal internal carotid artery, and final interpretations were reached by consensus. For interpretation of the MRA, these radiologists were blinded to patient clinical information and findings from the conventional angiography. Only axial source images of the TOF MRA were used for image evaluation. All images were reviewed on a PACS system. For analysis, MR imaging signal intensities were measured in a 6- to 10-mm² circular region of interest over the carotid plaque. IPH was defined as the presence of a hyperintense signal intensity within the carotid plaque greater than 150% of the signal intensity of the adjacent neck muscle on TOF source images.⁸

Outcome

Neurologic evaluation was performed at baseline, immediately and 24 hours after the procedure, at the time of any change in clinical symptoms, before patient discharge, and 1 month afterward by a stroke neurologist. The evaluation consisted of the NIHSS and the modified Rankin Scale.

The primary outcome measure was the combined incidence of any stroke, MI, or death during the 30-day periprocedural period. Stroke was defined as an acute neurologic event with focal symptoms and signs, lasting for 24 hours or more, that were consistent with focal cerebral ischemia. A major stroke was defined as stroke symptoms associated with a NIHSS score of 9 or higher 30 days after the procedure. A minor stroke was defined as stroke symptoms associated with a NIHSS score of 8 or less. MI was defined as the combination of elevated cardiac enzymes (creatinine kinase-MB or troponin level) to a value 2 or more times the upper limit of normal, plus chest pain.

The secondary outcome measures were as follows: 1) technical success, defined as successful deployment of all devices, filter retrieval, and poststent diameter stenosis <30% using the NASCET method; 2) hyperperfusion syndrome, defined as the occurrence, either singly or in combination, of an ipsilateral throbbing headache with or without nausea, vomiting, ipsilateral focal seizures, or focal neurologic deficit without radiographic evidence of infarction¹⁵; and 3) ICH associated with hyperperfusion syndrome, defined as CT evidence of intraparenchymal or SAH accompanied by hyperperfusion syndrome. The patients were assessed clinically at the follow-up visit 30 days after CAS. Follow-up CT angiography or conventional angiography was not performed within 30 days.

Statistical Analysis

Patients were divided into the IPH group or the non-IPH group for comparison. Statistical analyses were performed with SPSS software (Version 15.0; SPSS, Chicago, Illinois). Comparison of baseline characteristics and clinical outcomes between the 2 groups was done with the χ-square test for categoric and binary data, and the Student t test for continuous data. Multiple logistic regression was run with the dependent variable as a primary outcome. The independent variables were IPH, age, sex, index event, cerebrovascular history, history of ischemic heart disease, and cerebrovascular risk factors. A value of P < .05 was considered significant.