Abstract: "Cardiac memory" describes an electrocardiographic T wave vector change, recorded during normal sinus rhythm that reflects the QRS complex vector during prior periods of ventricular pacing or arrhythmia. In this brief review we consider the mechanisms responsible for cardiac memory, which offers a unique window for relating molecular determinants of repolarization to their expression in the function of ion channels and in the electrophysiology of the heart. Understanding the steps that translate the molecular mechanisms for memory into clinical expression in this relatively straightforward model facilitates our comprehension of the complex pathways that order normal cardiac repolarization and repolarization changes.