Modeling high-frequency pacing with a discrete cardiac strand
A computer model of a one-dimensional cardiac strand composed of separate cells connected by junctions was used to determine stimulation thresholds for pacing with 2-ms bursts of high-frequency monophase pulses. Two models of cardiac strand were used: a strand with junctions modeled by purely resistive regions, and a strand with junctions modeled by resistance and capacitance connected in series. The simulations were repeated for frequencies ranging from 0.25 to 10 kHz, and yielded strength-frequency curves for cathodal and anodal pacing. When the junctions were represented by pure resistivities, the curves obtained from the model disagreed with those from animal experiments. The inclusion of junctional capacitance of sizable value (120-160 pF) was necessary to bring modeling results in agreement with experiments.
