Cardiac memory-persistent T wave changes after ventricular pacing.

Cardiac memory is an uncommonly recognized entity in which T wave inversions on electrocardiogram (EKG) appear consistent with ischemia. Persistent deep T wave inversions are seen after return of normal depolarization in leads where the T waves were normal before pacing. These changes are generally recognized to occur in association with artificial pacemakers but may occur with other entities with intrinsic ventricular ectopic focus of depolarization, such as intermittent left bundle branch block. Although consideration of ischemia should be given priority, awareness of the benign nature of cardiac memory may allow some patients to avoid unnecessary work-up and admission. Sometimes the diagnosis cannot be confirmed definitively in the Emergency Department (ED) because many patients who have pacemakers also have coronary artery disease and only after a negative work-up for ischemia can one retrospectively presume cardiac memory as the likely etiology.