Concomitant changes in ventricular depolarization and repolarization and long-term outcomes of biventricular pacing

Background: Biventricular (BiV) pacing increases transmural repolarization heterogeneity due to epicardial to endocardial conduction from the left ventricular (LV) lead. However, limited evidence is available on concomitant changes in ventricular depolarization and repolarization and long-term outcomes of BiV pacing. Therefore, we investigated associations of BiV pacing-induced concomitant changes in ventricular depolarization and repolarization with mortality (i.e., LV assist device, heart transplantation, or all-cause mortality) and sustained ventricular arrhythmia endpoints. Methods: Consecutive BiV-defibrillator recipients with digital preimplantation and postimplantation electrocardiograms recorded between 2006 and 2015 at Duke University Medical Center were included. We calculated changes in QRS duration and corrected JT (JTc) interval and split them by median values. For simplicity, these variables were named QRS _decreased (≤ −12 ms), QRS _increased (> –12 ms), JTc _decreased (≤22 ms), and JTc _increased (> 22 ms) and subsequently used to construct four mutually exclusive groups. Results: We included 528 patients (median age, 68 years; male, 69%). No correlation between changes in QRS duration and JTc interval was observed (P =.295). Compared to QRS _decreased/JTc _increased, increased risk of the composite mortality endpoint was associated with QRS _decreased/JTc _decreased (hazard ratio [HR] = 1.62; 95% confidence interval [CI] = 1.09-2.43), QRS _increased/JTc _decreased (HR = 1.86; 95% CI = 1.27-2.71), and QRS _increased/JTc _increased (HR = 2.25; 95% CI = 1.52-3.35). No QRS/JTc group was associated with excess sustained ventricular arrhythmia risk (P =.400). Conclusion: Among BiV-defibrillator recipients, QRS _decreased/JTc _increased was associated with the most favorable long-term survival free of LV assist device, heart transplantation, and sustained ventricular arrhythmias. Our findings suggest that improved electrical resynchronization may be achieved by assessing concomitant changes in ventricular depolarization and repolarization.