Fig. 7.

Incidence of Ca²⁺ alternans in control (Ctrl) induced pluripotent stem cell-derived cardiomyocytes (iPSC-CM) pre-treated with EMD57033 (5 µM). A Normalised representative traces of Ca²⁺ transients (CaT) at 0.5 Hz (upper), 2 Hz (middle) and 5 Hz (lower) in untreated Ctrl (left) and in Ctrl iPSC-CM pre-treated with EMD57033 (right). Arrowheads indicate electrical stimulation and illustrate when beat-to-beat alterations are present. B Ca²⁺ transient time constant of decay (τ). C Alternans threshold frequency. Number of myocytes without alternans is shown in boxes above. D Kaplan–Meier plot showing the percentage of cells without alternans in relation to the respective pacing. n = number of iPSC-CM from 2 to 5 batches. Data are mean ± SEM. *P < 0.05 and ***P < 0.001 vs. Ctrl using the Mann–Whitney U test (B, C), and the Gehan–Breslow–Wilcoxon test (D)