Mechanical and structural characteristics of carotid plaques by combined analysis with echotracking system and MR imaging.

OBJECTIVES 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.

[1]  S. Crozier,et al.  High-resolution MR imaging of the cervical arterial wall: what the radiologist needs to know. , 2009, Radiographics : a review publication of the Radiological Society of North America, Inc.

[2]  C. Zarins,et al.  Compensatory enlargement of human atherosclerotic coronary arteries. , 1987, The New England journal of medicine.

[3]  Stéphane Laurent,et al.  Multiaxial Mechanical Characteristics of Carotid Plaque: Analysis by Multiarray Echotracking System , 2007, Stroke.

[4]  Elinor Miller,et al.  Comparison of the efficacy and safety of rosuvastatin versus atorvastatin, simvastatin, and pravastatin across doses (STELLAR* Trial). , 2003, The American journal of cardiology.

[5]  G. V. R. Born,et al.  INFLUENCE OF PLAQUE CONFIGURATION AND STRESS DISTRIBUTION ON FISSURING OF CORONARY ATHEROSCLEROTIC PLAQUES , 1989, The Lancet.

[6]  P J Brands,et al.  Assessment of the spatial homogeneity of artery dimension parameters with high frame rate 2-D B-mode. , 2001, Ultrasound in medicine & biology.

[7]  E. Boerwinkle,et al.  From vulnerable plaque to vulnerable patient: a call for new definitions and risk assessment strategies: Part I. , 2003, Circulation.

[8]  P. Boutouyrie,et al.  Association between local pulse pressure, mean blood pressure, and large-artery remodeling. , 1999, Circulation.

[9]  Antonio Colombo,et al.  From vulnerable plaque to vulnerable patient: a call for new definitions and risk assessment strategies: Part II. , 2003, Circulation.

[10]  Hiroshi Kanai,et al.  Elasticity Imaging of Atheroma With Transcutaneous Ultrasound , 2003, Circulation.

[11]  Stéphane Laurent,et al.  Carotid Plaque, Arterial Stiffness Gradient, and Remodeling in Hypertension , 2008, Hypertension.

[12]  W D Wagner,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. , 1995, Arteriosclerosis, thrombosis, and vascular biology.

[13]  Chun Yuan,et al.  Classification of Human Carotid Atherosclerotic Lesions With In Vivo Multicontrast Magnetic Resonance Imaging , 2002, Circulation.

[14]  H. Iwao,et al.  [Vascular remodeling]. , 2000, Nihon rinsho. Japanese journal of clinical medicine.

[15]  C. Tracy,et al.  American College of Cardiology Clinical Expert Consensus Document on Standards for Acquisition, Measurement and Reporting of Intravascular Ultrasound Studies (IVUS). A report of the American College of Cardiology Task Force on Clinical Expert Consensus Documents. , 2001, Journal of the American College of Cardiology.

[16]  E. Vicaut,et al.  Mannheim Carotid Intima-Media Thickness Consensus (2004–2006) , 2006, Cerebrovascular Diseases.