Propafenone toxicity can cause significant QRS widening and markedly abnormal ventricular activation pattern. Aberrant ventricular activation upon its resolution is known to produce persistent T-wave changes known as "cardiac memory" (CM). A 74-year-old woman presented with a severely abnormal electrocardiogram consistent with propafenone toxicity. As her QRS complex narrowed, T-wave inversions developed with the T-wave axis and resolution kinetics consistent with CM. Abnormal ventricular activation due to propafenone toxicity can result in CM development.