Characterization of Complicated Carotid Plaque With Magnetic Resonance Direct Thrombus Imaging in Patients With Cerebral Ischemia

Abstract

Background-Thromboembolic disease secondary to complicated carotid atherosclerotic plaque is a major cause of cerebral ischemia. Clinical management relies on the detection of significant (Ͼ70%) carotid stenosis. A large proportion of patients suffer irreversible cerebral ischemia as a result of lesser degrees of stenosis. Diagnostic techniques that can identify nonstenotic high-risk plaque would therefore be beneficial. High-risk plaque is defined histologically if it contains hemorrhage/thrombus. Magnetic resonance direct thrombus imaging (MRDTI) is capable of detecting methemoglobin within intraplaque hemorrhage. We assessed this as a marker of complicated plaque and compared its accuracy with histological examination of surgical endarterectomy specimens. Methods and Results-Sixty-three patients underwent successful MRDTI and endarterectomy with histological examination. Of these, 44 were histologically defined as complicated (type VI plaque). MRDTI demonstrated 3 false-positive and 7 false-negative results, giving a sensitivity and specificity of 84%, negative predictive value of 70%, and positive predictive value of 93%. The interobserver (ϭ0.75) and intraobserver (ϭ0.9) agreement for reading MRDTI scans was good. Conclusions-MRDTI of the carotid vessels in patients with cerebral ischemia is an accurate means of identifying histologically confirmed complicated plaque. The high contrast generated by short T 1 species within the plaque allows for ease of interpretation, making this technique highly applicable in the research and clinical setting for the investigation of carotid atherosclerotic disease. Key Words: thrombus Ⅲ plaque Ⅲ carotid arteries Ⅲ imaging Ⅲ cerebral ischemia A therothrombotic carotid disease is a major cause of cerebral ischemia. Embolization from the surface of an atherosclerotic plaque to cerebral vessels can result in occlusion, which, if sufficiently prolonged, will result in cerebral infarction. More transient vascular occlusion may result in temporary ischemia, producing a neurological deficit that recovers with little or no residual brain damage. Clinically, transient ischemic attacks (TIAs) provide a warning of further cerebral ischemic events; Ϸ10% of patients who sustain a TIA, left untreated, will suffer a definitive stroke in the following year, 1 followed by a rate of 5% per annum. A warning TIA therefore offers the chance to intervene to prevent future permanent cerebral damage. The North American 2 and European 3 endarterectomy trials have both shown the positive benefit of surgery in patients with significant stenosis. The trials also indicate that lesser degrees of carotid disease are responsible for a significant number of strokes, but the risks of surgery matched or outweighed the benefits. Techniques have been sought to further define those among the group with moderate stenosis who are at high risk.In 1995, Stary et al, 4 for the American Heart Association, defined different atherosclerotic subtypes, the purpose being to pathologically identify plaque more likely to ...

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