Cardiac Mechanics
- Group leaders
- Associate Professor Martyn Nash, Associate Professor Alistair Young
- Group members
- Honorary Associate Professor Brett Cowan, Professor Peter Hunter , Dr Ian LeGrice, Associate Professor Poul Nielsen, Dr Rob Kirton, Dr Nic Smith
- Graduate students
- Kevin Augenstein, Holger Schmid
- Associates
- Dr Rob Doughty, Mr Dane Gerneke, Dr Espen Remme
Overview
The mechanical function of the heart is governed by the contractile properties of the cells, the mechanical stiffness of the muscle and connective tissue, and the pressure and volume loading conditions on the organ. We have shown that heart muscle has a complex layered, fibrous 3D architecture that has a profound effect on its mechanical behaviour. Accurate Finite Element models of heart shape, tissue architecture and mechanical properties have been developed to realistically predict normal and pathological mechanical processes. Tissue testing devices have also been developed to characterise the mechanical properties of heart muscle during extension, compression and shear. One area of active research is the development of better material laws that can be used to interpret in-vitro and in-vivo tissue behaviour. Sophisticated analysis methods are being developed for the understanding of diastolic and systolic mechanisms of dysfunction. These techniques will allow improved diagnosis of patients and evaluation of treatment.
Mechanical orthotropy of cardiac tissue
Heart muscle fibre and connective tissue organisation gives rise to mechanical behaviour that varies depending on the loading orientation. This is known as mechanical orthotropy of cardiac tissue.
Tissue stretch versus load
Recordings of tissue stretch versus load (mechanical stress) registered against the fibre-sheet microstructural directions provide the necessary information to characterise the mechanical properties of heart muscle and the construction of microstructurally-based material laws.
Computational model of the ventricles
An anatomically accurate computational model of the left and right ventricles, including quantitative descriptions of the muscle architecture, allows application of realistic boundary conditions (pressure, volume) and orthotropic mechanical properties.
Heart cycle simulations
Heart cycle simulations validated against clinical and experimental recordings of organ deformation (from MRI, ultrasound, etc) provide regional estimates of ventricular wall stress. Increased wall stress is known to be correlated with oxygen demand and used as a marker for disease.
Recent publications
- Augenstein K., Cowan B., LeGrice I.J., Nielsen P.M.F. and Young A.A. Method and apparatus for soft tissue material parameter estimation using tissue tagged magnetic resonance imaging. J. Biomech. Engr., 127:148-157, 2005.
- LeGrice I.J., Pope A. and Smaill B. The architecture of the heart: Myocyte organization and cardiac extracellular matrix. In “Interstitial fibrosis in heart failure”. F Villareal Ed., Springer, Academic Press. pp3-21, 2004.
- Remme E.W., Young A.A., Augenstein K.F., Cowan B. and Hunter P.J. Extraction and quantification of left ventricular deformation modes. IEEE Trans. Biomed Eng., 51(11):1923-31, 2004.
- Remme E.W., Hunter P.J., Smiseth O., Stevens C., Rabben S.I., Skulstad H. and Angelsen B.B. Development of an in-vivo method for determining material properties of passive myocardium. J.Biomech., 37(5):769-78, 2004.
- Stevens C., Remme E., LeGrice I. and Hunter P. Ventricular mechanics in diastole: material parameter sensitivity. J. Biomech.,. 36(5):737-48, 2003.
- Nash M.P. and Hunter P.J. Computational mechanics of the heart: from tissue structure to ventricular function. J. Elast., 61(1/3):113-141, 2000.
Funding sources
- HRCNZ
- NHF
- Wellcome Trust (UK)
Collaborators, clinical and industry links
- UCSD
- University of Oxford
- Dr Chris Occleshaw, Auckland
- Dr Ralph Stewart, Mercy Angiography
- Siemens
- Varian