Moderate Carotid Artery Stenosis: MR Imaging-Depicted Intraplaque Hemorrhage Predicts Risk of Cerebrovascular Ischemic Events in Asymptomatic Men

Abstract

Conclusion: In men with moderate carotid artery stenosis, intraplaque hemorrhage detected by magnetic resonance imaging (MRI) is a marker of future ipsilateral cerebrovascular events. Summary: By 2032, mortality from stroke in the United States is predicted to rise to 275,000 patients per year (Stroke 2003;34:2109-12). Intraplaque hemorrhage (IPH) is a marker of carotid plaque instability. Necrotic core size and plaque volume are features that contribute to plaque rupture. It is possible to use MRI to identify IPH. The authors studied 91 men (mean age, 74.8 years; range, 47-88 years). They were selected from those who had attended a vascular clinic between 2003 and 2006 and by duplex ultrasound imaging had a 50% to 70% internal carotid artery stenosis that was asymptomatic. Patients in whom IPH was detected on MRI were identified retrospectively, and 75 men with 98 eligible arteries were included. The follow-up was for a minimum of 1 year (mean, 24.92 months; range, 12-43 months). Ipsilateral cerebrovascular events were compared between carotid arteries with and those without MRI-depicted IPH. There were 36 carotid arteries (36.7%) with MRI-depicted IPH. In the carotid distributions with IPH, six cerebrovascular events (2 strokes and 4 transient ischemic attacks) occurred during follow-up. No clinical events occurred in carotid arteries without IPH. Cox regression analysis indicated MRI-depicted IPH was associated with an increased risk of cerebrovascular events (hazard risk, 3.59; 95% confidence interval, 2.48-4.71; P < .001). Given that there were no events in IPH-negative patients, the negative predictive value for the absence of IPH for clinical outcome was 100%. Comment: The unstated, but intriguing, suggestion of this study is that if a patient presents with an asymptomatic carotid stenosis, risk stratification with MRI may be appropriate. If the MR study shows no evidence of IPH, then perhaps the patient can be watched and endarterectomy avoided, thus reducing the large number of endarterectomies performed in asymptomatic patients, most of whom will never have a neurologic event. This small study is not going to change clinical practice. If analysis were performed only for stroke, it is likely that only two strokes would not be statistically different from the neurologic event rate in the patients without intraplaque hemorrhage. The observations are interesting, but larger studies that use stroke-only as an end point will be required before patients with >60% duplex-detected asymptomatic internal carotid artery stenosis by duplex scanning are also routinely evaluated with an MRI study of their carotid.