Computationally efficient model of myocardial electromechanics for multiscale simulations

Figures

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  Fig 1. Simulation of steady-state muscle contractions. Calculated Ca2+-dependencies of A1 and A2 (red and green, respectively, A), normalised CaTn concentration in the overlap (red) and non-overlap (green) zones of a sarcomere (B), normalized active tension (C) and A12 and A22 (D) at different sarcomere length are shown. The length values are shown next to the curves in μm.

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  Fig 2. The time courses of model variables and major Ca2+ flows during a twitch contraction at constant sarcomere length of 2.2 μm and stimulation rate of 1 Hz. A: u, c (in μM), cSR and cSS (in mM), A1, A2, R, and Ta/Ta_max (active tension normalised for its maximal isometric value at saturating Ca2+ concentration at the same sarcomere length); B: INCX, ICaL, and Irel/50 (in μM×s−1).

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  Fig 3. The effect of sarcomere length on twitch contractions at the stimulation rate 1 Hz. A: isometric twitches before and after a change of sarcomere length from 1.9 to 2.2 μm; B, C: calculated normalised active tension and Ca2+ concentration in cytosol for twitches shown by arrows of the same colour in A.

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  Fig 4. Changes in twitch amplitude (normalised active tension) upon changes of stimulation frequency. The stimulation frequency changed from 1 Hz to 2 Hz (upper trace) and from 1 Hz to 0.8 Hz (lower trace).

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  Fig 5. Contraction dependence on the interstimulus interval. A: the dependence of calculated active tension normalized for its steady-state value at saturating Ca2+ concentration at the same sarcomere length (squares), maximal (circles) and minimal (diamonds) Ca2+ concentration c in cytosol (right scale) on the stimulation frequency. B: the dependence of peak twitch tension normalized for its value at 1 Hz stimulation on the interval duration after 1 Hz stimulation.

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  Fig 6. Calculated active tension during isometric twitches at different stimulations rates at sarcomere length 2.2 μm. The rates are shown next to curves in min−1. A: active tension normalized for its maximal value at saturating Ca2+ concentration; B: same calculated tension traces normalized for their peak values.

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  Fig 7. The results of simulation of isotonic contractions under different load. From top to bottom: sarcomere length, total and passive tension, δ, c, and n multiplied by a factor 2.5. Ca2+-transient c for isometric contraction is shown by dashed line.