[Cardiac memory of the ECG following ventricular pacing]

During abnormal pacemaker depolarization, abnormal repolarization occurs and persists in normal QRS beats often seen in alternation with paced beats. The T-wave direction of normal beats is typically similar to the direction of the QRS complex during pacing, hence the term cardiac memory. The normal nonpaced beats have shown a sensitivity of 92% and a specificity of 100% for cardiac memory in the presence of T-wave inversions (TWI) in the precordial and inferior (II, III and aVF) leads with a positive T wave in aVL, a positive or isoelectric T wave in lead I, and the maximal precordial TWI being greater than the TWI of lead III, discriminating it from ischemic precordial TWI. In the latter, TWI are also seen in leads aVL and I.