Generic Cardiac Ionic Models
These single cell CellML models run in OpenCOR (v0.4.1) to reproduce the action potential traces from Figures 6 and 7 of the publication. Constant current depolarising and hyperpolarising stimuli were added to the models to compensate for the lack of electrotonic coupling current present in vitro as well as the simplified 2D disc models described in the publication but absent in the single cell CellML models.
Models are provided for the following cell types:
- Central sino-atrial node
- Peripheral sino-atrial node
- Right atrial
- Left atrial
- Pulmonary vein antrum
ABSTRACT - A 3D model of atrial electrical activity has been developed with spatially heterogeneous electrophysiological properties. The atrial geometry, reconstructed from the male Visible Human dataset, included gross anatomical features such as the central and peripheral sinoatrial node (SAN), intra-atrial connections, pulmonary veins, inferior and superior vena cava, and the coronary sinus. Membrane potentials of myocytes from spontaneously active or electrically paced in vitro rabbit cardiac tissue preparations were recorded using intracellular glass microelectrodes. Action potentials of central and peripheral SAN, right and left atrial, and pulmonary vein myocytes were each fitted using a generic ionic model having three phenomenological ionic current components: one time-dependent inward, one time-dependent outward, and one leakage current. To bridge the gap between the single-cell ionic models and the gross electrical behaviour of the 3D whole-atrial model, a simplified 2D tissue disc with heterogeneous regions was optimised to arrive at parameters for each cell type under electrotonic load. Parameters were then incorporated into the 3D atrial model, which as a result exhibited a spontaneously active SAN able to rhythmically excite the atria. The tissue-based optimisation of ionic models and the modelling process outlined are generic and applicable to image-based computer reconstruction and simulation of excitable tissue.
Amr Al Abed, Tianruo Guo, Nigel H. Lovell, and Socrates Dokos, Optimisation of Ionic Models to Fit Tissue Action Potentials: Application to 3D Atrial Modelling, Computational and Mathematical Methods in Medicine, vol. 2013, Article ID 951234, 16 pages, 2013. doi:10.1155/2013/951234.
Each cell-type was modelled a generic ionic model consisting of two generic voltage- and time-gated currents (one inward and one outward) in addition to a leakage current.
Each generic current was gated using two voltage- and time-dependent gates, p and q. Each gate was in turn controlled by two voltage-dependent rate variables alpha and beta.
This generic model formulation is modular and could be expanded to add extra currents as required. In this case we found that two currents generic currents in addition to a leakage current were sufficient to reproduce action potentials recorded experimentally under baseline conditions in each of the myocyte types.