Risk Factors Predictive of Carotid Artery Stenting-Associated Subclinical Microemboli

Carotid artery stenting (CAS) with an embolic protection device (EPD) is a valid treatment alternative for experienced physicians to carotid endarterectomy (CEA) for patients with severe carotid artery stenosis, particularly high-risk patients.1,2 Despite absence of neurological symptoms, subclinical microemboli related to CAS procedures are common.3,4,5,6,7,8,9 Multiple studies have shown correlation of microemboli with cognitive decline in patients who underwent surgical procedures.10,11,12,13,14,15 Therefore, procedure-related microembolization is increasingly recognized as a promising outcome measure for carotid interventions. Studies have demonstrated that age, diabetes, and preoperative neurological events and open-cell stent design are predicative factors for CAS-associated 30-day strokes.5,8,16,17,18,19 However, these studies only evaluated clinically evident embolic events. There are very limited studies evaluating the risk factors for subclinical microemboli associated with CAS. The purpose of this study was to examine a relatively homogeneous group of CAS patients and to determine the risk factors predictive of subclinical microemboli associated with CAS procedures. Magnetic resonance imaging (MRI) offers extensive useful data by delineating the anatomy and presence of infarction. A diffusion-weighted magnetic resonance image (DWI) sequence in combination with an apparent diffusion coefficient (ADC) map has been shown to be a sensitive and reliable imaging modality to detect microembolic events following carotid interventions.3,4,5,6,8,9 Whereas conventional MRI may reveal positive findings within 8 to 12 hours of onset of acute infarction, DWI may be positive within minutes. Studies from our institution showed consistent and reliable readings of identifying carotid intervention-related lesions on DWI among experienced neuroradiologists with a low interobserver variability.8,9 In this study, MRI-evident procedure-related embolic lesions will be systemically examined.