Low extracellular potassium prolongs repolarization and evokes early afterdepolarization in human induced pluripotent stem cell-derived cardiomyocytes

Figures

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  Fig. 1.. Representative traces of field potentials at baseline and at 1 mM [K+]Ex in cardiomyocyte clusters and the dose-dependent prolongation in field potentials corresponding to [K+]Ex. (A) Recording of a representative field potential event by MEA at WT baseline (upper trace) and its corresponding field potential event in the presence of 1 mM [K+]Ex (lower trace). (B) and (C) are equivalent to (A), but show LQT1A (B) and LQT1B (C), respectively. Scale bars: 40 µV (A), 10 µV (B) 10 µV in abscissa, (C) and the ordinate is 100 ms. Dashed lines (A-C) indicate 0 µV. Arrows indicate the endpoint of FPD.

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  Fig. 2.. Representative current clamp recordings of spontaneous actions potentials extracted from single ventricular-like cardiomyocyte baselines and their corresponding responses to 1 mM [K+]Ex and dose-dependent prolongation of APD90 induced by [K+]Ex. (A-C) Representative baselines (upper traces) and the corresponding effect of 1 mM [K+]Ex (lower traces) for (A) WT, (B) LQT1A and (C) LQT1B, respectively. Scale bars: abscissa 40 mV and ordinate 2 s. Dashed lines (A-C) indicate 0 mV.

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  Fig. 3.. Representative current clamp recordings of arrhythmia in LQT1A cardiomyocytes. (A) A cardiomyocyte without early afterdepolarization (EAD) in baseline (upper trace) and with (EAD) only observed at 1 mM [K+]Ex (lower trace). (B) Depicts a cardiomyocyte with EADs in baseline (upper trace) and EADs were prolonged at 1 mM [K+]Ex (lower trace). Arrows point to the beginning and end of the arrhythmic Phase 2. Scale bars: 40 mV in abscissa and 2 s in ordinate. Dashed lines (A and B) indicate 0 mV. Note that EADs were only found in LQT1A cardiomyocytes with more prolonged baseline APDs (see Fig. 2B for a comparison).