Abstract
This case concerns a 24-year-old female who developed malignant ventricular tachyarrhythmia a few weeks after pacemaker implantation for complete heart block. Apparently, right ventricular pacing caused significant repolarization abnormalities in both native and paced rhythms with marked QT prolongation and substantial electrical instability. This case highlights other intriguing phenomena in the puzzle of cardiac repolarization and how pacing therapy may alter this complex process providing arrhythmic substrate in vulnerable subjects. Though such arrhythmic events are clinically rare, vulnerable patients or with suspected myocardial disease that may cause QT prolongation should be carefully followed in the course of pacing therapy.