Clinical Research
Multidetector-Row Computed Tomography in Evaluation of Atherosclerotic Carotid Plaques Complicated with Intraplaque Hemorrhage

https://doi.org/10.1016/j.avsg.2008.05.008Get rights and content

Our aim was to determine the sensitivity and specificity of multidetector-row computed tomography (CT) in detecting atherosclerotic carotid plaques complicated with intraplaque hemorrhage. We examined carotid plaques from 31 patients operated for carotid artery stenosis. Results of preoperative multidetector-row CT analysis of carotid plaques were compared with results of histological analysis of the same plaque areas. Carotid endarterectomy was performed within 1 week of multidetector-row CT. American Heart Association classification of atherosclerotic plaques was applied for histological classification. Median tissue density of carotid plaques complicated with intraplaque hemorrhage was 22 Hounsfield units (HU). Median tissue density of noncalcified segments of uncomplicated plaques was 59 HU (p = 0.0062). The highest tissue density observed for complicated plaques was 31 HU. Multidetector-row CT detected plaques complicated with hemorrhage with sensitivity of 100% and specificity of 64.7%, with tissue density of 31 HU as a threshold value. Multidetector-row CT showed a high level of sensitivity and a moderate level of specificity in detecting atherosclerotic carotid plaques complicated with hemorrhage.

Introduction

Large randomized controlled trials demonstrated benefit of carotid endarterectomy (CEA) in symptomatic patients with high-degree carotid artery stenosis.1, 2 Asymptomatic patients benefit less from CEA, with absolute risk reduction of only about 1% annually during 5-year follow-up.3, 4 Therefore, a large number of asymptomatic patients must be operated to prevent a small number of neurological events. The total number of operated asymptomatic patients may be lowered if subgroups of asymptomatic patients who benefit most from CEA could be identified. Several studies have shown a higher incidence of neurological incidents in patients with so-called soft plaques (plaques predominantly consisting of lipids, tissue debris, and hemorrhage).5, 6, 7, 8, 9, 10 Ultrasound analysis of carotid plaques demonstrated that hypoechoic plaques represent an independent risk factor for stroke incidence in adults aged 65 years or older.11 Takaya et al.12 followed asymptomatic patients for 38 months and showed that patients with intraplaque hemorrhage on initial magnetic resonance imaging (MRI) had a 5.2 times higher incidence of cerebrovascular events. The American Heart Association (AHA) classification of atherosclerotic plaques defines eight types of plaques, according to histological content (Table I).13, 14 Atherosclerotic carotid plaques complicated with intraplaque hemorrhage (AHA type VIb) are considered unstable and are associated with a higher incidence of cerebrovascular events.12, 15, 16, 17 Computed tomographic (CT) angiography demonstrated high accuracy in diagnosing carotid artery stenosis.18, 19, 20, 21, 22 An additional feature of CT is its ability to measure tissue density (expressed as number of Hounsfield units [HU]). Thus, it can provide some information about the type of analyzed tissue. Atherosclerotic carotid plaques with lower tissue density on multidetector-row CT (MDCT) are associated with a lower incidence of cerebrovascular events.6, 7 While single slice CT showed conflicting results in determining carotid plaque composition, MDCT showed good correlation of findings with histological analysis of coronary plaques.23, 24, 25, 26, 27 Histological analysis of coronary plaques showed that remodeling of atherosclerotic plaque changes its histological content. Therefore, the period between imaging and histological analysis should be as short as possible.28 We compared results of MDCT and histological analysis and calculated sensitivity and specificity of MDCT in detection of AHA type VIb atherosclerotic carotid plaques (plaques complicated with intraplaque hemorrhage, most often containing a mixture of lipids, hemorrhage, and necrotic debris). CEA was performed within 1 week of MDCT.

Section snippets

Materials and Methods

Carotid plaques from 31 consecutive patients operated for carotid artery stenosis were included in this prospective study. There were 21 male and 10 female patients, aged 51-87, median 70, years. There were six symptomatic and 25 asymptomatic patients (Table II). Patients who experienced cerebral insult, transient ischemic attack, or amaurosis fugax on the side of the affected carotid artery within 6 months of MDCT were considered symptomatic.

Indications for CEA were symptomatic patients with

Results

There were 14 (45%) AHA VIb plaques and 17 (55%) plaques of other AHA types (V, VII, and VIII). Median MDCT tissue density of type VIb plaques was 22 HU (range –17 to 31), and median tissue density of noncalcified segments of noncomplicated plaques was 59 HU (range –6 to 150) (p = 0.0062, Mann-Whitney U-test) (Fig. 5). ROC analysis showed 100% sensitivity and 64.7% specificity of MDCT in detecting plaques complicated with intraplaque hemorrhage, with tissue density of 31 HU as a threshold value

Discussion

This study showed that MDCT could detect atherosclerotic carotid plaque complicated with hemorrhage with 100% sensitivity, with tissue density of 31 HU as a threshold value. Previous studies showed inconclusive results regarding the accuracy of single-slice CT in analyzing plaque composition.23, 24 De Weert et al.29 showed good correlation between in vivo MDCT findings and histological findings; however, in their analysis of 15 carotid plaques, the period between MDCT evaluation and

Conclusion

MDCT showed a very high level of sensitivity and a moderate level of specificity in detecting hemorrhage within atherosclerotic carotid plaque. Plaques with tissue density over 31 HU on MDCT were not complicated with intraplaque hemorrhage. Technical advancements of CT equipment may probably increase the specificity of the method.

References (53)

  • D.W. Dodick et al.

    Evaluation and management of asymptomatic carotid artery stenosis

    Mayo Clin Proc

    (2004)
  • C.B. Rockman et al.

    Natural history and management of the asymptomatic, moderately stenotic internal carotid artery

    J Vasc Surg

    (1997)
  • A.S. Jahromi et al.

    Sensitivity and specificity of color duplex ultrasound measurement in the estimation of internal carotid artery stenosis: a systematic review and meta-analysis

    J Vasc Surg

    (2005)
  • North American Symptomatic Carotid Endarterectomy Trial Collaborators. Beneficial effect of carotid endarterectomy in symptomatic patients with high-grade carotid stenosis. N Engl

    J Med

    (1991)
  • European Carotid Surgery Trialist's Collaborative Group. Medical Research Council European Carotid Surgery Trial. Interim results for symptomatic patients with severe (70-99%) or with mild (0-29%) carotid stenosis

    Lancet

    (1991)
  • Executive Committee for the Asymptomatic Carotid Atherosclerosis Study. Endarterectomy for asymptomatic carotid artery stenosis

    JAMA

    (1995)
  • A. Halliday et al.

    Asymptomatic Carotid Surgery Trial (ACST) Collaborative Group. Prevention of disabling and fatal strokes by successful carotid endarterectomy in patients without recent neurological symptoms: randomised controlled trial

    Lancet

    (2004)
  • M.L.M. Grønholdt et al.

    Ultrasonic echolucent carotid plaques predict future strokes

    Circulation

    (2001)
  • J.M. Serfaty et al.

    for the CARMEDAS Study Group. Plaque density on CT, a potential marker of ischemic stroke

    Neurology

    (2006)
  • K.R. Nandalur et al.

    Calcified carotid atherosclerotic plaque is associated less with ischemic symptoms than is noncalcified plaque on MDCT

    AJR Am J Roentgenol

    (2005)
  • European Carotid Plaque Study Group

    Carotid artery plaque composition—relationship to clinical presentation and ultrasound B-mode imaging

    Eur J Vasc Endovasc Surg

    (1995)
  • G. Carra et al.

    Carotid plaque morphology and cerebrovascular events

    Int Angiol

    (2003)
  • E.B. Mathiesen et al.

    Echolucent plaques are associated with high risk of ischemic cerebrovascular events in carotid stenosis: the Tromso Study

    Circulation

    (2001)
  • J.F. Polak et al.

    Hypoechoic plaque at US of the carotid artery: an independent risk factor for incident stroke in adults aged 65 years or older. Cardiovascular Health Study

    Radiology

    (1998)
  • N. Takaya et al.

    Association between carotid plaque characteristics and subsequent ischemic cerebrovascular events: a prospective assessment with MRI—initial results

    Stroke

    (2006)
  • H.C. Stary et al.

    A definition of advanced types of atherosclerotic lesions and a histological classification of atherosclerosis: a report from the Committee on Vascular Lesions of the Council an Arteriosclerosis, American Heart Association

    Circulation

    (1995)
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