Changes in Ventricular Repolarization After Right Ventricular and Left Bundle Branch Pacing

Left bundle branch pacing (LBBP) has recently emerged as an alternative to the widely used right ventricular pacing (RVP), which presents limitations related to the induced ventricular activation dyssynchrony. Here, we measured the QRS complex duration (QRSd) and an index of sympathetic modulation of ventricular repolarization, called Periodic Repolarization Dynamics (PRD), one day and one year after pacemaker implantation. In our cohort of patients with right and left bundle branch block, LBBP induced a decrease in QRSd (median [IQR] at baseline: $\mathbf{1 6 0. 5}$ [20.20] ms, after one day: 133.5 [25.25], after one year: $133[23.8] \mathrm{ms}$), thus indicating higher activation synchronization. On the other hand, RVP showed no significant changes (155.0 [15.15], 156. 5 [30.30] and 150.5 [34.34] ms). PRD was reduced after one-day pacing for both LBBP and RVP, but returned to baseline values after one year. In conclusion, LBBP shows improved activation synchronization as compared to RVP, with no significant differences in sympathetically-mediated repolarization oscillations between the two pacing techniques.