(A) Heat maps of average synchrony across combinations of gap junctional resistances (Rgap) and cleft widths for 20 linearly coupled PSC-CMs with either uniform (left) and nonuniform (right) NaCh distributions. (B) Color maps denote the temporal evolution of transmembrane potential (Vm) across all 20 PSC-CMs at 3 different levels of Rgap (1×105 kΩ, left; 1×106 kΩ, middle; 1×107 kΩ, right) when NaChs were distributed uniformly (top) and nonuniformly (bottom); cleft width was 10 nm. When Rgap=1×106 kΩ and NaChs were nonuniformly distributed (middle, bottom), myocytes 16-19 were synchronized but remained asynchronous from the rest. (C) Instantaneous synchrony vs. time across Rgap values in panel (B); NaChs were uniformly distributed, and cleft width was 10 nm. (D) Instantaneous synchrony vs. time across different cleft widths when Rgap=1×107 kΩ and NaChs were uniformly and nonuniformly distributed. Differences between the traces were more pronounced at particular instances in time (inset). (E) Line plots of individual PSC-CM cycle length (CL) vs. beat number across Rgap values in panel (B); NaChs were uniformly distributed, and cleft width was 10 nm. (F) Line plots of cycle length vs. beat number demonstrating slight changes between uniform and nonuniform NaCh distributions when Rgap=1×107 kΩ. Differences were more pronounced for slower beating PSC-CMs (inset).