Figure 1: AP shape and stability in hiPSC-CM (iCell® Cardiomyocytes, CDI, 14-21 days in vitro). Typical whole-cell recordings of ventricular, atrial, and nodal-like cardiomyocytes (A). Stability plots of APD90 (B) and APD50/90 (C) for 5 iPSC-CM. All experiments were performed with CytoPatch™ 2 in current-clamp mode, with external pacing (0.5 ms, 2 nA, at 3-s intervals), at 21-22°C. External solution (in mM): 140 NaCl, 2.5 KCl, 2 MgCl2, 2 CaCl2, 10 HEPES, 10 Glucose, 15 Sucrose, pH 7.40, 320 ± 5 mOsm/kg.; internal solution (in mM): 100 K Gluconate, 20 KCl, 1 CaCl2, 1 MgCl2, 10 HEPES, 11 EGTA-KOH, 4 ATP-Mg2+, 3 Phosphocreatine-Na2-H2O, 9 Sucrose, pH 7.20, 290 mOsm/kg.