Quantitative study of the effect of tissue microstructure on contraction in a computational model of rat left ventricle.
Tissue microstructure, in particular the alignment of myocytes (fibre direction) and their lateral organisation into sheets, is fundamental to cardiac function. We studied the effect of microstructure on contraction in a computational model of rat left ventricular electromechanics. Different fibre models, globally rule-based or locally optimised to DT-MRI data, were compared, in order to understand whether a subject-specific fibre model would enhance the predictive power of our model with respect to the global ones. We also studied the impact of sheets on ventricular deformation by comparing: (a) a transversely isotropic versus an orthotropic material law and (b) a linear model with a bimodal model of sheet transmural variation. We estimated ejection fraction, wall thickening and base-to-apex shortening and compared them with measures from cine-MRI. We also evaluated Lagrangian strains as local metrics of cardiac deformation. Our results show that the subject-specific fibre model provides little improvement in the metric predictions with respect to global fibre models while material orthotropy allows closer agreement with measures than transverse isotropy. Nonetheless, the impact of sheets in our model is smaller than that of fibres. We conclude that further investigation of the modelling of sheet dynamics is necessary to fully understand the impact of tissue structure on cardiac deformation.
Department of Computer Science, University of Oxford, Oxford, United Kingdom.
Valentina
V
Carapella
Department of Computer Science, University of Oxford, Oxford, United Kingdom.
Rafel
R
Bordas
Department of Computer Science, University of Oxford, Oxford, United Kingdom.
Pras
P
Pathmanathan
Radcliffe Department of Medicine, Division of Cardiovascular Medicine, University of Oxford, Oxford, United Kingdom.
Maelene
M
Lohezic
Radcliffe Department of Medicine, Division of Cardiovascular Medicine, University of Oxford, Oxford, United Kingdom.
Jurgen E
JE
Schneider
National Heart and Lung Institute, Imperial College, London, United Kingdom.
Peter
P
Kohl
Department of Computer Science, University of Oxford, Oxford, United Kingdom.
Kevin
K
Burrage
Institute of Biomedical Engineering, Department of Engineering Science, University of Oxford, Oxford, United Kingdom.
Vicente
V
Grau
D000818:Animals; D005260:Female; D006352:Heart Ventricles; D008297:Male; D008955:Models, Cardiovascular; D009200:Myocardial Contraction / Q000502:physiology*; D051381:Rats; D016276:Ventricular Function / Q000502:physiology*