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Figure 9.8 (a) Electrical activation times (indicated by color bar) in response to
right RV pacing as recorded using electrode arrays. Data were obtained from a
normal canine heart that was subsequently reconstructed using DTMRI.
Activation times are displayed on the epicardial surface of a finite-element
model fitted to the DTMRI reconstruction data. Fiber orientation on the
epicardial surface, as fitted to the DTMRI data by the FEM model, is shown by
the short line segments. (b) Activation times predicted using a computational
model of the heart mapped in (a). To view this figure in color, see the
companion web site for Systems Biology , http://www.oup.com/us/sysbio.
Nonetheless, these results demonstrate the feasibility of combined
experimentation and modeling of electrical conduction in specific
imaged and reconstructed hearts.
CONCLUSION
This chapter has reviewed modeling research in three broad areas:
(1) models of single ventricular myocytes; (2) methods for the recon-
struction and modeling of ventricular geometry and microanatomy;
and (3) integrative modeling of the cardiac ventricles. We have seen
that the level of biophysical detail, and hence the accuracy and pre-
dictability of current ventricular myocyte models, is considerable.
Nonetheless, much remains to be done.
One emerging area of research is modeling of mitochondrial energy
production. Approximately 2% of cellular ATP is consumed on each
heartbeat. The major processes consuming ATP in the myocyte are
muscle contraction, activity of the SR Ca 2+ -ATPase, and Na-K pumping.
Cellular ATP levels also influence ion channel function including the
sarcolemmal ATP-modulated K channel [90]. Recently, an integrated
thermokinetic model of cardiac mitochondrial energetics comprising
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