Propagation velocity profile in a cross-section of a cardiac muscle bundle from PSpice simulation

Table 1 Summary of experiments to determine the cross-sectional profile of impulse propagation in a bundle of cardiac fibers (20 × 10 model).

	No. of Gj-channels	R_ol2(KΩ)	R_BT(KΩ)	Θ₁(cm/sec)	Θ₁₀(cm/sec)	Θ₁/Θ₁₀Ratio	Shape
A	0	200	200	36.6	17.0	2.15	Bell-shaped
B	1	200	200	36.8	19.7	1.86	Bell-shaped
C	10	200	200	46.6	44.6	1.04	Bullet-shaped
D	100	200	200	397	397	1.00	Flat
E	0	2000	200	32.9	29.0 ^#28.1	1.13 1.17	Accent bullet-shaped dimple
F	10	2000	200	46.6	44.6	1.04	Bullet-shaped
G	100	2000	200	397	397	1.00	Flat
H	0	2000	2000	62.2	32.9	1.89	Bell narrower and Θ approx doubled
I	100	2000	2000	386	397	0.97	Flat
J	0	20	200	38.1	14.4	2.65	Bell-shaped
K	0	20	20	13.0	14.4	0.90	Inverse
L	10	20	200	46.7	43.8	1.07	bell-shaped, but low ratio
M	100	20	200	397	397	1.00	Flat
N	0	50	200	37.4	15.4	2.43	Bell-shaped
O	0	800	200	35.1	22.7	1.55	Bell-shaped

The gj-channels were inserted at the cell junctions of each chain.
Θ₁ ---- velocity at edge of bundle.
Θ₁₀ ---- velocity at middle of bundle.
20 × 10 model ---- 20 parallel chains of 10 cells each.
All 20 cells at left end of bundle were stimulated simultaneously using rectangular current pulses of 0.25 nA and 0.25 ms duration.
Bundle was symmetrical at the top and the bottom (including two grounds).
All parameters were set at standard values, including R_jc of 25 MΩ (50 MΩ ÷ 2).
Standard value for R_ol2 was 200 KΩ, and for R_BT was 200 KΩ.
Voltage markers were placed only on cells 1, 5 and 10 of each chain (i.e., total of 60 traces).
# This second value is for θ₆ (also θ₁₅)_, because this is where maximum slowing occurred (because of the dimple).

ISSN: 1742-4682