Effect of cardiac resynchronization therapy on ventricular repolarization: a meta-analysis

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.