Noninvasive Identification of the Unstable Carotid Plaque

https://doi.org/10.1007/s10016-006-9000-8Get rights and content

Intraplaque hemorrhage, enlarging lipid cores, and their proximity to the flow lumen are important determinants of carotid plaque rupture and neurological complications. We developed an image-analysis method for B-mode ultrasound, pixel distribution analysis (PDA), for pre-procedural identification of these high-risk features in carotid plaques. This technique may improve selection of patients for carotid endarterectomy and carotid artery stenting. Forty-two patients with high-grade carotid stenosis in 45 arteries, 18 symptomatic and 27 asymptomatic, underwent preoperative ultrasound. Intraplaque hemorrhage, lipid, fibromuscular tissue, calcium, lipid core area, and distance from the flow lumen were quantified using pixel intensities of tissues in control subjects. These findings were contrasted between symptomatic and asymptomatic plaques and correlated with histology. Inter- and intraobserver variabilities were determined for this technique. Pixel intensities of control tissues were discrete and significantly different from each other (median: blood 0, lipid 27, muscle 45.5, fibrous tissue 204, and calcium 245). There was more intraplaque hemorrhage (p < 0.001) and lipid (p = 0.002) but less calcium (p < 0.001) within symptomatic plaques. Lipid cores were larger (p = 0.005) and their distance from the flow lumen was lower (p = 0.01) in symptomatic plaques. Intraplaque hemorrhage, lipid, fibromuscular tissue, calcium, lipid core size, and distance from flow lumen measured by PDA correlated with histology. No significant inter- or intraobserver variabilities were observed in these measurements. PDA accurately identified more intraplaque hemorrhage and lipid, less calcium, and larger lipid cores located closer to the flow lumen in symptomatic patients with carotid stenosis. These data indicate that PDA may be used to identify high-risk carotid atherosclerotic plaques and thereby improve the selection of patients requiring treatment.

Section snippets

INTRODUCTION

Carotid atherosclerotic plaque histology has identified several features associated with atheroembolic neurological events. Plaques with large lipid cores1 located close to the flow lumen,2 fibrous cap disruption,3 surface ulceration4 and intraplaque hemorrhage5 have been classified as type VI (complex) plaques.6 These histological features have been associated with atheroembolic events in patients with carotid stenosis (CS). Some of these features may also predispose the plaque to

Patients

After institutional review board approval, informed consent was obtained from all participants. Twenty healthy subjects underwent US scanning to determine pixel intensity of individual tissues. Forty-two patients with 45 CSs were determined to require CEA based on North American Symptomatic Carotid Endarterectomy Trial (NASCET, ≥50% stenosis, symptomatic)21, 22 or Asymptomatic Carotid Atherosclerosis Study (ACAS, ≥60% stenosis, asymptomatic)23 recommendations. The degree of stenosis was

Patient Population

There were 45 carotid plaques from 42 patients included in the study (34 males and 8 females). The mean age was 68 years (range 51–91). The degree of stenosis (based on preoperative US) ranged 70–99%. Eighteen plaques were obtained from symptomatic patients (stroke n = 6, transient ischemic attack n = 9, and amaurosis fugax n = 3), and 27 were from asymptomatic patients. The mean interval between symptoms and CEA in symptomatic patients was 12 weeks. The control group comprised 10 male and 10

DISCUSSION

Randomized controlled trials demonstrating the efficacy of CEA at preventing stroke have utilized the degree of internal carotid artery stenosis as the only criterion for selecting patients at high risk for stroke.21, 22, 23 However, these trials also noted that the majority of patients with high-grade stenoses remained stroke-free even when receiving medical therapy alone.24 It has therefore been proposed that factors in addition to the degree of stenosis may be responsible for determining

REFERENCES (30)

  • HC 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 on Arteriosclerosis, American Heart Association

    Arterioscler Thromb Vase Biol

    (1995)
  • SC Carr et al.

    Histology and clinical significance of the carotid atherosclerotic plaque: implications for endovascular treatment

    J Endovasc Surg

    (1997)
  • HJ Barnett et al.

    Plaque morphology as a risk factor for stroke

    JAMA

    (2000)
  • WE Faught et al.

    Color-flow duplex scanning of carotid arteries: new velocity criteria based on receiver operator characteristic analysis for threshold stenoses used in the symptomatic and asymptomatic carotid trials

    J Vasc Surg

    (1994)
  • E Goes et al.

    Tissue characterization of atheromatous plaques: correlation between ultrasound image and histological findings

    J Clin Ultrasound

    (1990)
  • Cited by (63)

    • The Unstable Carotid Plaque

      2022, Anesthesiology Clinics
      Citation Excerpt :

      A cutoff point of 8 mm2 has been suggested to have a good diagnostic value.38 Proximity of the necrotic plaque core to the lumen is associated with symptomatic presentation.39,40 Higher carotid intima-medial thickness is also associated with higher stroke risk.41

    • Asymptomatic carotid stenosis is associated with cognitive impairment

      2017, Journal of Vascular Surgery
      Citation Excerpt :

      The transducer was placed directly over the carotid artery segment containing the plaque to obtain a longitudinal image; it was then swept from the base of the neck to the angle of the mandible to identify and record the cross-sectional image where the tightest stenosis was visualized. The images were digitally recorded and analyzed offline with a computer-assisted image analysis program by independent observers blinded to clinical findings, using previously described approaches.24-26 The longitudinal sectional image that showed the largest amount of plaque was selected for each patient for analysis.

    • Imaging of high-risk carotid plaques: ultrasound

      2017, Seminars in Vascular Surgery
    View all citing articles on Scopus
    View full text