Afterdepolarizations and triggered activities induced by H₂O₂ in electrically stimulated ventricular myocytes. (A) Continuous recording of action potentials during exposure to H₂O₂ (100 μm) from a ventricular myocyte electrically stimulated at 5-s intervals. (B) Changes in action potential duration at 90% repolarization (APD₉₀) during exposure to H₂O₂ (100 μm). (C) Action potentials on an expanded time scale recorded at points indicated by characters (a, b, c, and d) in A. Filled circles indicate action potentials evoked by electrical stimulation, and arrows indicate membrane voltage fluctuations accompanied by triggered activities. Experiments were conducted at 35°–37°C. V_m represents the membrane potential.