Volume 40.4 of the journal Textile Progress, this book reviews textile-structured electrodes, interactive textile devices, for wearable electrocardiogram (ECG). It describes the human cardiac bioelectricity signal using mechanism and acquisition methods by commercial medical electrodes and textile-based electrodes, comparing the advantages and disadvantages of these types of electrodes. The text also discusses the conduction of ECG signal within the human body through skin-electrode interface and in electrodes. It presents the designing principles of textile electrodes based on the performance requirements of electrodes and includes a new evaluation system of textile electrodes.