Human-induced pluripotent stem cell-atrial-specific cardiomyocytes and atrial fibrillation

Figure 4 Action potential of cardiac muscle. Red arrow up represents outward current, green arrow down represents inward currents. Action potential has 5 states: 4, resting; 0, upstroke; 1, early repolarization; 2, plateau; 3, final repolarization. APD: Action potential duration; I_CaL: L-type Ca²⁺ current; I_f: Pacemaker current; I_K: Delayed rectification currents; I_K1: Inward rectifier current; I_KACh: Acetylcholine-activated inward-rectifying potassium current; I_Kr: Rapid; I_Ks: Slow; I_Kur: Ultra-rapid; I_Na: Sodium current; I_to: Transient outward current; NCX, Na +/Ca²⁺ exchanger.