Fig. 13.

Low Na⁺/Ca²⁺ exchanger current (I_NCX) promotes fluctuations in diastolic Ca²⁺ concentration in both in silico populations, whereas high Na⁺/Ca²⁺ exchanger conductance (G_NCX) and low release current (J_rel) correlate with the presence of a spike-and-dome Ca²⁺ transient (CaT) in the Grandi-based population only. A–C: proportions of models and examples exhibiting distinct CaT morphologies in the Maleckar population calibrated with action potential (AP) + L-type Ca²⁺ current (I_CaL) + inward rectifier K⁺ current (I_K1) data and parameters underpinning the three CaT phenotypes (C). D–F: showcase analogous results for the Grandi-based population following AP + I_CaL + I_K1 calibration. In A–C, morphologically normal CaTs, Ca²⁺ oscillations in diastole, and spontaneous Ca²⁺ release phenotypes are plotted in black, dark gray, and light gray, respectively. In D–F, morphologically normal CaTs, spike-and-dome CaTs, and spontaneous Ca²⁺ release models are shown in black, dark gray, and light gray, respectively. Ca²⁺ oscillations and spontaneous Ca²⁺ release are referred to as fluctuations in diastolic Ca²⁺.