Impact of plaque haemorrhage and its age on structural stresses in atherosclerotic plaques of patients with carotid artery disease: an MR imaging-based finite element simulation study
- 237 Downloads
Plaque haemorrhage (PH) in atherosclerotic plaques is associated with recurrent thromboembolic ischaemic events. The healing process predominantly involves the repair of the plaque rupture site and the replacement of fresh PH with chronic PH, which is either reabsorbed or replaced by fibrous tissue. The extent to which the presence of PH, and its type i.e. fresh or chronic, affects plaque stability remains unexplored. Finite element analysis (FEA)-based biomechanical stress simulations can provide quantification of the percentage contribution of PH and its types to the biomechanical stresses of plaques, thereby providing information about its role in plaque stability. Fifty-two patients with atherosclerotic carotid disease underwent high resolution magnetic resonance (MR) imaging of their carotid arteries in a 1.5 Tesla MR system. Twenty-three patients had MR-identifiable PH and were selected. Only those images of these patients were used for simulations, which had evidence of PH. Manual segmentation of plaque components, such as lipid pool, fibrous tissue, calcium and PH, was done using carotid MR images. Plaque components and vessel wall were modelled as isotropic, incompressible hyperelastic materials with non-linear properties undergoing deformation under patient-specific blood pressure loading. Two dimensional structure-only FEA was used for quantification of maximum critical stress (M-CStress) of plaques. The median M-CStress of symptomatic patients with fresh PH was 159 kPa (IQR: 114–253). Because PH usually occurs within the lipid pool, when the simulation was repeated with lipid pool replacing fresh PH to simulate the pre-rupture plaque state, M-CStress was reduced by 26% [118 kPa (IQR: 79–189) (P = 0.001)]. When fresh PH was replaced with chronic PH it resulted in a 30% reduction in the M-CStress [118 kP (IQR: 79–189), (P = 0.001)]. PH affects stresses within atheroma to various degrees depending on its type, thereby influencing plaque stability to a different extent, with fresh PH significantly increasing the biomechanical stresses. Plaque component-dependent stress analysis has the potential of identifying the critical nature of various plaque components.
KeywordsMagnetic resonance imaging Stroke Transient Ischaemic attacks Atherosclerosis Finite element analysis Biomechanical stress Plaque Haemorrhage
Dr. Umar Sadat is supported by a Medical Research Council UK & Royal College of Surgeons of England Joint Clinical Research Training Fellowship. This research has also been supported by a Biomedical Research Centre National Institute of Health Research (BRC NIHR) grant.
Umar Sadat and Zhongzhao Teng have equal contribution in writing this manuscript.
- 2.Saam T, Yuan C, Chu B, Takaya N, Underhill H, Cai J, Tran N, Polissar NL, Neradilek B, Jarvik GP, Isaac C, Garden GA, Maravilla KR, Hashimoto B, Hatsukami TS (2007) Predictors of carotid atherosclerotic plaque progression as measured by noninvasive magnetic resonance imaging. Atherosclerosis 194:e34–e42PubMedCrossRefGoogle Scholar
- 4.Li ZY, Howarth S, Tang T, Graves M, U-King-Im JM, Gillard JH (2007) Does calcium deposition play a role in the stability of atheroma? Location may be the key. Cerebrovasc Dis 24:452–459Google Scholar
- 8.Sadat U, Teng Z, Young VE, Graves MJ, Gillard JH (2010) Three-dimensional volumetric analysis of atherosclerotic plaques: a magnetic resonance imaging-based study of patients with moderate stenosis carotid artery disease. Int J Cardiovasc Imaging. [Epub ahead of print]Google Scholar
- 9.Sadat U, Li ZY, Young VE, Graves MJ, Boyle JR, Warburton EL, Varty K, O’Brien E, Gillard JH (2010) 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. J Neurol Neurosurg Psychiatry 81(3):286–289PubMedCrossRefGoogle Scholar
- 10.Sadat U, Weerakkody RA, Bowden DJ, Young VE, Graves MJ, Li ZY, Tang TY, Gaunt ME, Hayes PD, Gillard JH (2009) Utility of high resolution MR imaging to assess carotid plaque morphology: A comparison of acute symptomatic, recently symptomatic and asymptomatic patients with carotid artery disease. Atherosclerosis 207(2):434–439PubMedCrossRefGoogle Scholar
- 11.Yuan C, Mitsumori LM, Ferguson MS, Polissar NL, Echelard D, Ortiz G, Small R, Davies JW, Kerwin WS, Hatsukami TS (2001) In vivo accuracy of multispectral magnetic resonance imaging for identifying lipid-rich necrotic cores and intraplaque hemorrhage in advanced human carotid plaques. Circulation 104:2051–2056PubMedCrossRefGoogle Scholar
- 14.Bathe KJ (2002) Theory and modeling guide vol I: ADINA; vol II: ADINA-F. ADINA R&D, Inc., WatertownGoogle Scholar
- 15.Teng Z, Sadat U, Li Z, Huang X, Zhu C, Young VE, Graves MJ, Gillard JH (2010) Arterial luminal curvature and fibrous-cap thickness affect critical stress conditions within atherosclerotic plaque: an in vivo MRI-based 2D finite-element study. Ann Biomed Eng. [Epub ahead of print]Google Scholar
- 21.Department of Health (2007) National stroke strategyGoogle Scholar
- 23.Kampschulte A, Ferguson MS, Kerwin WS, Polissar NL, Chu B, Saam T, Hatsukami TS, Yuan C (2004) Differentiation of intraplaque versus juxtaluminal hemorrhage/thrombus in advanced human carotid atherosclerotic lesions by in vivo magnetic resonance imaging. Circulation 110:3239–3244PubMedCrossRefGoogle Scholar
- 30.Li ZY, Howarth SP, Tang T, Graves MJ, U-King-Im JM, Trivedi RA, Kirkpatrick PJ, Gillard JH (2007) Structural analysis and magnetic resonance imaging predict plaque vulnerability: a study comparing symptomatic and asymptomatic individuals. J Vasc Surg 45:768–775Google Scholar
- 31.Sadat U, Teng Z, Young VE, Walsh SR, Li ZY, Graves MJ, Varty K, Gillard JH (2010) Association between biomechanical structural stresses and morphological characteristics of atherosclerotic carotid plaques and subsequent ischaemic cerebrovascular events—a longitudinal in vivo MRI-based finite-element study. Eur J Vasc Endovasc Surg (in press)Google Scholar