Page 118 - YORAM RUDY BOOK FINAL

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Figure 4.4. Simulated effects of transmural I and I expression levels on action potential
to
Ks
morphology and ECG waveforms (“pseudo-ECG”). Shown (top to bottom) are data for endocardial,
M, and epicardial cells, and the corresponding pseudo-ECG (bottom row). Left column: control.
Middle column: homogeneous I density. Right column: in absence of I . In control, the V
Ks
to
m
gradient during repolarization, created by the heterogeneity of I density, inscribes the T-wave.
Ks
Complete repolarization of the epicardium coincides with peak of the T-wave, complete repolar-
ization of the mid-myocardium (M) coincides with the end of the T-wave (vertical dotted lines).
Arrows indicate the I - mediated notch in epicardial and M cells, which reflects as the J-wave
to
(Osborn wave) on the pseudo-ECG. Removing I heterogeneity (middle column) alters the
Ks
repolarization sequence, which now follows the (endocardium to epicardium) activation
sequence. Because epicardium repolarizes later than midmyocardium, V gradient and T-wave
m
are inverted. I block (right column; gray curves, compare with control black curves) removes the
to
phase-1 notch of the action potential and suppresses the ECG J-wave. Reproduced from Gima and
Rudy [247] with permission from Wolters Kluwers Health, Inc.