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.

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

Objective:

Cardiac resynchronization therapy (CRT) was thought to have a proarrhythmic effect on ventricular repolarization. But the results of previous studies were inconsistent. The aim of this study was to determine the effect of CRT on ventricular repolarization.

Methods:

A meta-analysis of studies focused on the effect of CRT on ventricular repolarization in patients undergoing CRT was conducted. Endpoints including QT interval (QT), JT interval (JT), QT dispersion(QTD) and interval between the peak to end of T wave (Tp-e).

Results:

A total of 14 studies were included in our meta-analysis. After pooling the data, no significant difference was observed in QT, JT and Tp-e between biventricular (BV) pacing and intrinsic ventricular rhythm. BV paced QTD was lower than intrinsic QTD, but the significance was ambiguous [mean difference (MD): -17.33, 95% CI -34.44 to -0.22, p=0.05]. Left ventricular (LV) paced Tp-e was significantly longer than intrinsic Tp-e (MD: 21.44, 95% CI 2.37 to 40.51, p=0.03). No significant difference was observed in QT, JT and QTD between LV pacing and intrinsic ventricular rhythm.

Conclusion:

In patients undergoing CRT, BV pacing has no deteriorating effect on ventricular repolarization, but LV pacing has a prolonging effect on Tp-e.

Tpeak - Tend and Tpeak - Tend /QT ratio as markers of ventricular arrhythmia risk in cardiac resynchronization therapy patients

BACKGROUND

Cardiac resynchronization therapy (CRT) increases transmural dispersion of repolarization (TDR) and can be pro-arrhythmic. However, overall arrhythmia risk was not increased in large-scale CRT clinical trials. Increased TDR as measured by T(peak ) -T(end) (TpTe) was associated with arrhythmia risk in CRT in a single-center study. This study investigates whether QT interval, TpTe, and TpTe/QT ratio are associated with ventricular arrhythmias in patients with CRT-defibrillator (CRT-D).

METHODS

Post-CRT-D implant electrocardiograms of 128 patients (age 71.3 years ± 10.3) with at least 2 months of follow-up at our institution's device clinic (mean follow-up of 28.5 months ± 17) were analyzed for QT interval, TpTe, and TpTe/QT ratio. Incidence of ventricular arrhythmias was determined based on routine and directed device interrogations.

RESULTS

Appropriate implantable cardioverter-defibrillator therapy for sustained ventricular tachycardia or ventricular fibrillation was delivered in 18 patients (14%), and nonsustained ventricular tachycardia (NSVT) was detected but did not require therapy in 58 patients (45%). Patients who received appropriate defibrillator therapy had increased TpTe/QT ratio (0.24 ± 0.03 ms vs 0.20 ± 0.04, P = 0.0002) and increased TpTe (105.56 ± 20.36 vs 87.82 ± 22.32 ms, P = 0.002), and patients with NSVT had increased TpTe/QT ratio (0.22 ± 0.04 vs 0.20 ± 0.04, P = 0.016). Increased QT interval was not associated with risk of ventricular arrhythmia. The relative risk for appropriate defibrillator therapy of T(p) T(e) /QT ratio ≥ 0.25 was 3.24 (P = 0.016).

CONCLUSION

Increased TpTe and increased TpTe/QT ratio are associated with increased incidence of ventricular arrhythmias in CRT-D. The utility of TpTe interval and TpTe/QT ratio as potentially modifiable risk factors for ventricular arrhythmias in CRT requires further study.

Differential effect of biventricular and right ventricular DDD pacing on coronary flow reserve in patients with ischemic cardiomyopathy

CRT and Coronary Flow Reserve.

BACKGROUND

Cardiac resynchronization therapy (CRT) has become a mainstay in heart failure management. There are also indications that upgrading of existing pacemakers to CRT systems may be of benefit. The aim of this study was to assess the effect of biventricular (BiV), compared with right ventricular (RV), pacing, on coronary flow reserve (CFR), in patients with ischemic cardiomyopathy.

METHODS AND RESULTS

From our database of heart failure patients implanted with BiV pacemakers, 20 patients (10 responders and 10 non-responders to CRT) were randomly selected. Left anterior descending artery coronary flow reserve was measured invasively, under BiV and RV pacing, using intracoronary adenosine to induce hyperemia. In all the 20 patients, there was a significant difference in the pairwise comparison between CFR recorded during BiV and RV pacing (mean difference 0.15, 95% confidence interval 0.07-0.23, P = 0.001). When comparing responders to non-responders, there was a significant difference as to the effect of BiV, compared with RV, pacing on CFR: mean difference (BiV minus RV CFR) was 0.26 ± 0.06 (95% confidence interval 0.13-0.39; P = 0.002), while in non-responders the difference was 0.04 ± 0.03 (95% confidence interval -0.02 to 0.10; P = 0.168).

CONCLUSION

BiV pacing is overall associated to higher CFR, compared with RV DDD pacing. This difference is almost exclusively attributable to the beneficial effect of CRT on coronary flow reserve in CRT-responders. This effect may contribute to the beneficial action of resynchronization in the failing heart and can be viewed in the context of reports of the usefulness of upgrading RV pacemakers to CRT systems.