  The results of a simulation study of the action potential duration (APD)
distribution and T-wave morphology taking into account the midmyocardial cells
(M-cells) concept are described. To investigate the effect of M-cells we
present a computer model in which ion channel action potential formulations are
incorporated into three-dimensional whole heart model. We implemented
inhomogeneous continuous action potential duration distribution based on
different distributions of maximal slow delayed rectifier current conductance.
Using the proposed action potential distribution procedure midmural zeniths
with longest action potential length were created as islands of model cells in
the depth of thickest areas of ventricular tissue. Different spatial functions
on layer indexes were simulated and their influences on electrocardiogram
waveforms were analyzed. Changing parameters of ion channel model we varied
duration of minimal and maximal action potential and investigated T-wave
amplitude, Q-Tpeak and QT intervals variations. The study demonstrated that the
proposed original APD distribution is reasonable and produces realistic
electrocardiographic waveforms.
