Structural analysis and magnetic resonance imaging predict plaque vulnerability: a study comparing symptomatic and asymptomatic individuals.
BACKGROUND
More than half of all cerebral ischemic events are the result of rupture of extracranial plaques. The clinical determination of carotid plaque vulnerability is currently based solely on luminal stenosis; however, it has been increasingly suggested that plaque morphology and biomechanical stress should also be considered. We used finite element analysis based on in vivo magnetic resonance imaging (MRI) to simulate the stress distributions within plaques of asymptomatic and symptomatic individuals.


METHODS
Thirty non-consecutive subjects (15 symptomatic and 15 asymptomatic) underwent high-resolution multisequence in vivo MRI of the carotid bifurcation. Stress analysis was performed based on the geometry derived from in vivo MRI of the carotid artery at the point of maximal stenosis. The finite element analysis model considered plaque components to be hyperelastic. The peak stresses within the plaques of symptomatic and asymptomatic individuals were compared.


RESULTS
High stress concentrations were found at the shoulder regions of symptomatic plaques, and the maximal stresses predicted in this group were significantly higher than those in the asymptomatic group (508.2 +/- 193.1 vs 269.6 +/- 107.9 kPa; P = .004).


CONCLUSIONS
Maximal predicted plaque stresses in symptomatic patients were higher than those predicted in asymptomatic patients by finite element analysis, suggesting the possibility that plaques with higher stresses may be more prone to be symptomatic and rupture. If further validated by large-scale longitudinal studies, biomechanical stress analysis based on high resolution in vivo MRI could potentially act as a useful tool for risk assessment of carotid atheroma. It may help in the identification of patients with asymptomatic carotid atheroma at greatest risk of developing symptoms or mild-to-moderate symptomatic stenoses, which currently fall outside current clinical guidelines for intervention.
Li
Zhi-Yong
ZY
University Department of Radiology, Cambridge University Hospitals NHS Foundation Trust, Cambridge, United Kingdom. ZYL22@cam.ac.uk <ZYL22@cam.ac.uk>
Howarth
Simon P S
SP
Tang
Tjun
T
Graves
Martin J
MJ
U-King-Im
Jean
J
Trivedi
Rikin A
RA
Kirkpatrick
Peter J
PJ
Gillard
Jonathan H
JH
D000368:Aged; D001696:Biomechanical Phenomena; D016893:Carotid Stenosis / Q000175:diagnosis* / Q000473:pathology / Q000503:physiopathology; D015331:Cohort Studies; D003198:Computer Simulation; D004548:Elasticity; D005260:Female; D020342:Finite Element Analysis; D006801:Humans; D018810:Magnetic Resonance Angiography; D008297:Male; D008875:Middle Aged; D008955:Models, Cardiovascular; D017711:Nonlinear Dynamics; D011237:Predictive Value of Tests; D012422:Rupture, Spontaneous / Q000175:diagnosis; D012720:Severity of Illness Index; D013314:Stress, Mechanical