Cardiac Memory T-wave Inversions Noted with Ventricular Pacing: A Possible Electrocardiographic Marker of Appropriate Conduction System Pacing.

Cardiac memory is a common condition occurring after a period of abnormal depolarization, such as with right ventricular apical pacing. With restoration of normal conduction, the T-wave "remembers" the direction of the QRS vector of the previously aberrantly conducted complexes, creating diffusely inverted T-waves on the electrocardiogram. The presence of diffuse T-wave inversions with this phenomenon may be confused with myocardial ischemia and may continue to be present for several weeks after restoration of normal conduction. Here, an interesting electrocardiogram obtained after pacemaker implantation showing the opposite effect, ie, the finding of memory T-waves occurring during pacing after a period of intrinsic atrioventricular nodal conduction, is presented. In this case, the patient had an underlying left bundle branch block, which subsequently normalized as a result of conduction system pacing. The memory T-waves became evident after pacing was performed, suggesting a potential marker for restoration of the normal ventricular activation sequence with left bundle branch pacing and normalization of the baseline intraventricular conduction defect.