A study of propagated and nonpropagated action potential upstrokes based upon experiments and modeling

The authors reevaluated the process of action potential propagation in a quantitative manner, using a spacially discrete cable model with an optimized membrane current model. The model reconstructs an action potential upstroke with a higher stroke velocity (V _max) of 451 V/s, which was comparable to that obtained from isolated myocytes (512±77 V/s). The gap junctional conductance ( G_j) was estimated based upon the conduction velocity (65±6 cm/s) along the long axis of papillary muscles. The estimated G_j was 6 mS/cm², that is 700 nS, which was within the range of the measured gap conductances from paired ventriculocytes. In the one-dimensional model, the V_max of the simulated propagating action potential was 322 V/s, which was larger than the V_max obtained from papillary muscles (θ_L) (237±25 V/s) by approximately 35%. In the two-dimensional hexagonal model, the simulated θ_L was 63 cm/s and the V_max amounted to 257 V/s, which was comparable to the experimental results