Biomedical Engineering Reference
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Fig. 7.5 Simulation results performed by mathematical model: ( A ) isometric contraction as a
function of time at different half sarcomere lengths from 0.95 to 1.1 µm ( solid curves ) compared
with experimental measurements ( crosses ) (Janssen and Hunter, 1995 ); ( B ) end-systolic curve for
the isometric contractions and the isotonic contraction traces (end of the trace is marked with
the symbol) at different afterloads from 10 to 80 kPa; ( C ) change in sarcomere length during
the isotonic contraction at different afterloads; ( D ) total amount of consumed ATP molecules per
myosin head during a cardiac cycle as a function of SSA for isometric ( solid curve ), isotonic
( dashed curve ) and physiologic ( dotted curve ) contraction
In Fig. 7.5 (A) simulation of isometric contraction at different half sarcomere
lengths from 0.95 to 1.1 µm (solid curve) is compared with experimental measure-
ments (crosses) (Janssen and Hunter, 1995 ). Similar to experimental data, simula-
tion results show that an increase in preload increases the maximal developed force
and the twitch duration.
End-systolic curve for the isometric contractions and the isotonic contraction
traces at different afterloads are compared in Fig. 7.5 (B). End-systolic points for
isotonic contraction lie close to the end-systolic curve for isometric contraction,
which is in agreement with several experimental studies.
The isotonic contraction showed in Fig. 7.5 (C) are simulated at afterloads from
10 to 80 kPa. To compare the contraction duration at isometric and isotonic con-
traction the duration is shorter in the isotonic case which is also in agreement with
experimental results (Brutsaert et al., 1978 ).
A linear relationship between ATP consumption and SSA was replicated by our
simulations for all considered contraction types (Fig. 7.5 (D)). The linear fit for re-
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