The document discusses the use of pluripotent stem cell-derived cardiomyocytes as substrates for automated ion channel and electrophysiological analysis systems. Specifically, it describes how cardiomyocytes can be selected from mouse embryonic stem cells using puromycin, and how these cells express appropriate cardiac ion channels. It also demonstrates that the cardiomyocytes can be used on automated patch clamp systems like PatchXpress and QPatch to measure cardiac ion currents like INa, ICa, and IK, and to study the effects of drugs on these currents. The document establishes pluripotent stem cell-derived cardiomyocytes as a physiologically relevant and reproducible model for high-throughput electrophysiology screening.