In 24 patients (14 males and 10 females, mean age 60±14) we assessed the effect of permanent ventricular pacing on ventricular repolarisation traced on ECG. We studied ventricular repolarisation abnormalities (VRA) such as changes in ST segment, T wave, corrected QT interval (QTc), QT dispersion (QTd) and the width of QRS complex of cardiotopic stimulations. VRA were classified into 6 categories. The measurements were taken prior to permanent pacemaker placement and 48 hours, 7, 14, 28 days and 12 months after insertion. The mean QTc, QTd and the width of QRS did not change significantly throughout the study. Ventricular repolarisation abnormalities first appeared 48 hours after pacemaker implantation to increase on 7-14 day and persist till day 26 when it was possible in 10 out of 24 patients to make the desired changes in programmable parameters (lowering the amplitude or changing the duration of impulse. Among the 10 patients whose pacemakers were reprogrammed we observed decreased VRA in 9 patients, while in 1 patient VRA did not change. Among the remaining 14 patients VRA decreased in 2, did not change in 10 and increased in 1 patient. Conclusions: 1. VRA of cardiotopic stimulations in patients with ventricular pacemakers are correlated with amplitude and with the stimulating impulse duration and tend to decrease when these parameters are lowered. 2. Permanent ventricular pacing changes the ECG of ventricular repolarisation of cardiotopic stimulations. It does not, however, increases the diversity of repolarisation assessed by QT dispersion.

Keywords: permanent pacing, ventricular repolarisation abnormalities (VRA), QT interval