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.