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.

Memory T-Waves, a Rare Cause of T-Wave Inversion in the Emergency Department

One of the rare causes of diffuse T-wave inversion (TWI) in electrocardiogram (ECG) is memory T-waves. This should be considered among the differentials of diffuse TWI in ECG of patients presenting to the emergency department (ED), especially when they have previous episodes of ventricular tachycardia (VT) or pacemaker implantation or Wolff-Parkinson-White syndrome. These TWIs are benign and do not require any treatment. However, it is of paramount importance for the emergency physician to differentiate it from ischemia-related T-wave changes. In the following case series, we report three cases of memory T-waves. Two of the cases had TWI in leads II, III, aVF, and V3 to V6 following reversion of VT. The other patient, with a VVI (Left ventricle paced, Left ventricle sensed, Inhibition to sensing) pacemaker, had memory T-waves in the ECG taken during normal sinus rhythm. In all the three patients, we considered memory T-waves to be the possible cause of TWI. The electrocardiographic diagnostic criteria for memory T-waves are positive T in lead aVL and positive/isoelectric T in the lead I; and precordial TWI >inferior TWI. These criteria are 92% sensitive and 100% specific. In the following case series, we also provide an algorithmic approach for patients with suspected memory T-waves in their 12-lead ECG when they present to the ED.