T-wave inversion after pacemaker implantation: a manifestation of cardiac memory

T-wave inversion (TWI) on electrocardiography often raises concern for myocardial ischemia or other structural heart disease. However, abnormal ventricular activation caused by cardiac pacing can induce transient repolarization changes known as cardiac memory. Awareness of this phenomenon is essential to avoid unnecessary diagnostic procedures. An 80-year-old woman underwent implantation of a dual-chamber pacemaker for symptomatic sick sinus syndrome. Her pre-operative electrocardiogram showed complete right bundle branch block with T-wave inversion limited to leads V1–V3. One week after pacemaker implantation, diffuse T-wave inversion developed in the precordial and limb leads. The patient remained asymptomatic, and echocardiography showed no evidence of myocardial ischemia. She had been ventricularly paced with a short atrioventricular delay for several days after implantation. The direction of T-wave inversion was consistent with that of the paced QRS complexes and resolved completely one month later. This case illustrates cardiac memory as a benign cause of diffuse T-wave inversion following pacemaker implantation. Clinicians should recognize this phenomenon after excluding myocardial ischemia to prevent unnecessary diagnostic testing.