Cardiac memory: The slippery slope twixt normalcy and pathology

“Cardiac memory” is an altered repolarization phenotype resulting from prior cardiac rate, rhythm, and/or activation changes. The various types of memory depend on biophysical properties of cardiac ion channels, trafficking of those channels, and/or epigenetic changes in the genes determining the channels. The processes that engage the memory function presage changes in function that ultimately can lead to pathological remodeling. Hence—rather than completely benign—memory may be a warning of disease to come. This article considers the forms, the mechanisms, and the clinical expression of cardiac memory.