Page 99 - YORAM RUDY BOOK FINAL

P. 99

Figure 3.18. Model schematic. A. WT and F2004L I models share the same structure; transition
Na
rate increases and decreases in the mutant relative to WT are represented as thick solid or thin
dashed arrows, respectively. B. The I models were introduced into the LRd ventricular cell
Na
model. C. A 1-dimensional fiber model containing 165 LRd cells connected through gap junctions
was used to simulate transmural right ventricular conduction. From Bébarová et. al. [227] courtesy
of The American Physiological Society.

The upstroke velocity for this secondary excitation was very slow (dV /dt = 4.08 mV/msec at
m max
cell 150). A surface plot showing action potentials (V ) in space and time for the mutant fiber is
m
provided in Figure 3.19B. A plot of axial current, I , into (negative) and out of (positive) cells along
axial
the fiber is shown in Figure 3.19D. Both inward and outward axial currents decrease with cell
number along the fiber indicating the decremental nature of I -supported conduction, with cells
Na
receiving and giving less depolarizing current as propagation proceeds. Of the cells shown, cell

150 (red) is excited after a long delay; the initial I is too small to cause excitation, but a
axial
later influx supported by the dome (phase 2) of depolarized upstream cells excites the cell. This
phase-2 axial current appears as late outward deflections in I for epicardial cells 120 (blue) and
axial
135 (green).