Finite element analysis of vulnerable atherosclerotic plaques: a comparison of mechanical stresses within carotid plaques of acute and recently symptomatic patients with carotid artery disease.
OBJECTIVE
There is considerable evidence that patients with carotid artery stenosis treated immediately after the ischaemic cerebrovascular event have a better clinical outcome than those who have delayed treatment. Biomechanical assessment of carotid plaques using high-resolution MRI can help examine the relationship between the timing of carotid plaque symptomology and maximum simulated plaque stress concentration.


METHODS
Fifty patients underwent high-resolution multisequence in vivo MRI of their carotid arteries. Patients with acute symptoms (n=25) underwent MRI within 72 h of the onset of ischaemic cerebrovascular symptoms, whereas recently symptomatic patients (n=25) underwent MRI from 2 to 6 weeks after the onset of symptoms. Stress analysis was performed based on the geometry derived from in vivo MRI of the symptomatic carotid artery at the point of maximum stenosis. The peak stresses within the plaques of the two groups were compared.


RESULTS
Patient demographics were comparable for both groups. All the patients in the recently symptomatic group had severe carotid stenosis in contrast to patients with acute symptoms who had predominantly mild to moderate carotid stenosis. The simulated maximum stresses in patients with acute symptoms was significantly higher than in recently symptomatic patients (median (IQR): 313x10(4) dynes/cm(2) (295 to 382) vs 252x10(4) dynes/cm(2) (236 to 311), p=0.02).


CONCLUSIONS
Patients have extremely unstable, high-risk plaques, with high stresses, immediately after an acute cerebrovascular event, even at lower degrees of carotid stenoses. Biomechanical stress analysis may help us refine our risk-stratification criteria for the management of patients with carotid artery disease in future.
Sadat
Umar
U
University Department of Radiology, Addenbrooke's Hospital, University of Cambridge, Cambridge CB2 0QQ, UK.
Li
Zhi-Yong
ZY
Young
Victoria E
VE
Graves
Martin J
MJ
Boyle
Jonathan R
JR
Warburton
Elizabeth A
EA
Varty
Kevin
K
O'Brien
Eoin
E
Gillard
Jonathan H
JH
D000208:Acute Disease; D000368:Aged; D000369:Aged, 80 and over; D001696:Biomechanical Phenomena; D016893:Carotid Stenosis / Q000175:diagnosis / Q000503:physiopathology*; D002544:Cerebral Infarction / Q000175:diagnosis / Q000503:physiopathology*; D003198:Computer Simulation; D003937:Diagnosis, Differential; D005260:Female; D020342:Finite Element Analysis; D006801:Humans; D007089:Image Enhancement; D007091:Image Processing, Computer-Assisted; D002546:Ischemic Attack, Transient / Q000175:diagnosis / Q000503:physiopathology*; D008279:Magnetic Resonance Imaging; D008297:Male