Multiscale modelling of cardiac mechanics

1. Multiscale modelling of cardiac mechanics David Nickerson, Carey Stevens, Martyn Nash, Peter Hunter 5th World Congress of Biomechanics, Munich, 2006

2. Overview • Porcine ventricular geometry: • existing geometric model; • same geometry, new topology. • Computational modelling and simulation framework. • Future work: • papillary muscles; • the Heart Physiome Project.

3. Existing Auckland porcine ventricular geometry model • Advantages: • good representation of ventricular geometry including the apex, valve rings, and underlying tissue microstructure; • 88 cubic Hermite finite elements. • Disadvantages: • full valve plane not connected to ventricles; • papillary muscle tissue flattened against endocardial surface; • numerical issues with mesh topology for other types of simulations;

4. Original Auckland porcine ventricular model

5. New Auckland porcine ventricular model • Re-engineered to take advantage of availability of increased computational power. • Could compensate for some of the disadvantages of the original model. • Advantages: • maintains good representation of ventricular geometry including the apex, valve rings, and underlying tissue microstructure; • fully integrated valve plane; • beginning of a papillary geometry; • mesh topology consistent with other applications; • Disadvantages: • 200 cubic Hermite finite elements

6. Ventricular geometric models

7. Ventricular geometric models

8. Tissue microstructure

9. Tissue microstructure

10. A computational modelling and simulation framework • CMISS (www.cmiss.org) for the description of geometric models & numerical simulations. • CellML (www.cellml.org) for the specification of most simulation specific mathematical models: • constitutive law, cellular models; • plug-and-play with new models. • Used in several case-studies to date: • constitutive law investigations in breast and cardiac tissue; • skeletal muscle mechanics and joint kinematics; • electromechanical studies of a left ventricular model.

11. A simple left ventricular electromechanical model: geometry

12. A simple left ventricular electromechanical model: boundary conditions displacement BCs electrical stimulus

13. A simple left ventricular electromechanical model: material properties mechanical stiffness cell types

14. A simple left ventricular electromechanical model: results

15. A simple left ventricular electromechanical model: biventricular pacing

16. Future work: papillary muscles

17. Future work: the heart Physiome Project

18. Acknowledgements • Bioengineering Institute @ The University of Auckland