Fig. 6.

FPD measured on MEA. (A) The effect of the beating rate on FPD in control and LQT2 cardiomyocytes (CMs). Control and LQT2 cardiomyocytes had a negative correlation with moderately high coefficients of determination (R²). The exponential function gave the best fit as determined by R² between different fitting functions. The LQT2 cardiomyocytes had significantly more prolonged FPD compared with controls, especially at low beating frequencies, as determined by nonlinear regression analysis (P=0.0136). (B) At beating rates below 50 beats per minute (bpm), the FPD of LQT2 cardiomyocytes differed significantly from control cardiomyocytes (*P<0.05) as determined by t-test. (C) Drug responses of control and LQT2 cardiomyocytes. Sotalol (19 μmol/l) and E-4031 (500 nmol/l for LQT2-specific cells and 700 nmol/l for control cells) was administered to the cardiomyocyte aggregates derived from control iPSCs and LQT2 iPSCs. For both cell lines, baseline and drug conditions for sotalol and E-4031 are shown. Arrows mark the site of pharmacologically induced EADs. With 500 nmol/l E-4031 there were no EADs observed in control cells.