title: Mechanical and structural characteristics of carotid plaques by combined analysis with echotracking system and MR imaging.
abstract: OBJECTIVE
  The purpose of this study was to correlate the arterial mechanics of carotid atherosclerotic plaques assessed from echotracking with their composition by high-resolution magnetic resonance imaging (HR-MRI).
  
  
  BACKGROUND
  Analysis of the relationship between mechanical parameters and structure of the plaque allows better understanding of the mechanisms leading to mechanical fatigue of plaque material, plaque rupture, and ischemic events. A specific longitudinal gradient of strain (reduced strain, i.e., lower radial strain at the plaque level than at the adjacent segment) has been shown in atherosclerotic plaques on the common carotid artery (CCA) in patients with hypertension, dyslipidemia, or type 2 diabetes mellitus. The structural abnormalities underlying this functional behavior have not been determined.
  
  
  METHODS
  Forty-six carotid plaques from 27 patients were evaluated; plaques were present at the site of the carotid bifurcation and extended to the CCA. Among the 27 patients, 9 had previous ischemic stroke ipsilateral to carotid stenosis (symptomatic) and 18 had not (asymptomatic). Mechanical parameters were measured at 128 sites on a 4-cm long CCA segment by noninvasive echotracking system, and strain gradient was calculated. Plaque composition was noninvasively determined by HR-MRI.
  
  
  RESULTS
  Complex plaques at HR-MRI (i.e., American Heart Association [AHA] stages IV to VIII) more often displayed a reduced strain than the simple plaques (i.e., AHA stages I to III; p = 0.046). HR-MRI verified complex plaques were associated with an outer remodeling upon echotracking, and had a lower distensibility than adjacent CCA (17.0 ± 5.0 MPa⁻¹ vs. 21.7 ± 7.3 MPa⁻¹; p = 0.007). An outer remodeling was observed in plaques with a lipid core at HR-MRI and was more frequent in symptomatic carotids.
  
  
  CONCLUSIONS
  These findings indicate that the longitudinal mechanics of "complex" plaques follows a specific pattern of reduced strain. They also suggest that reduced strain, associated with an outer remodeling, may be a feature of high-risk plaques.
authors.affiliation: Department of Pharmacology and INSERM U970, Hôpital Européen Georges Pompidou, Paris, France.
authors.forename: Hélène
authors.initials: H
authors.lastname: Beaussier
authors.forename: Olivier
authors.initials: O
authors.lastname: Naggara
authors.forename: David
authors.initials: D
authors.lastname: Calvet
authors.forename: Robinson
authors.initials: R
authors.lastname: Joannides
authors.forename: Evelyne
authors.initials: E
authors.lastname: Guegan-Massardier
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Gerardin
authors.forename: Michelle
authors.initials: M
authors.lastname: Iacob
authors.forename: Brigitte
authors.initials: B
authors.lastname: Laloux
authors.forename: Erwan
authors.initials: E
authors.lastname: Bozec
authors.forename: Jérémy
authors.initials: J
authors.lastname: Bellien
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Touze
authors.forename: Ingrid
authors.initials: I
authors.lastname: Masson
authors.forename: Christian
authors.initials: C
authors.lastname: Thuillez
authors.forename: Catherine
authors.initials: C
authors.lastname: Oppenheim
authors.forename: Pierre
authors.initials: P
authors.lastname: Boutouyrie
authors.forename: Stéphane
authors.initials: S
authors.lastname: Laurent
mesh_terms: D000368:Aged; D001696:Biomechanical Phenomena; D002340:Carotid Artery Diseases / Q000150:complications / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000473:pathology; D017536:Carotid Artery, Common / Q000000981:diagnostic imaging* / Q000473:pathology*; D016009:Chi-Square Distribution; D005260:Female; D005602:France; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D008955:Models, Cardiovascular; D058226:Plaque, Atherosclerotic / Q000150:complications / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000473:pathology; D011237:Predictive Value of Tests; D011379:Prognosis; D018570:Risk Assessment; D012307:Risk Factors; D012422:Rupture, Spontaneous; D013314:Stress, Mechanical; D014463:Ultrasonography