Conduction system pacing versus biventricular pacing: Reduced repolarization heterogeneity in addition to improved depolarization

Abstract

Introduction: His-bundle pacing (HBP) and left-bundle-area pacing (LBAP) are conduction system pacing (CSP) modalities increasingly used as alternatives to conventional biventricular pacing (BiVP). While effects of CSP on ventricular depolarization have been reported, effects on ventricular repolarization have not. Methods: QRS duration (QRSd) and validated ECG parameters of ventricular repolarization associated with arrhythmic risk (T-peak-to-T-end Transmural , T-peak-to-Tend Total , T-peak dispersion, QTc, QTc dispersion) were analyzed post-implant in 107 patients: 60 with CSP (HBP: n = 35, LBAP: n = 25) and 47 with BiVP. T-wave memory resolution and QTc shortening were analyzed on ECGs obtained ≥25 days postimplant. Twenty blinded measurements were obtained by both authors to assess Interobserver variability.Results: Although QRSd was shorter with HBP versus LBAP (119 ± 7 ms vs. 132 ± 9 ms, p = .02), there were no significant differences in any repolarization parameters between these methods of CSP. However, when comparing CSP (HBP + LBAP) to BiVP, both QRSd (125 ± 5 ms vs. 147 ± 7 ms, p < .0001) and repolarization parameters (T-peak-to-T-end Transmural : 83 ± 5 ms vs. 107 ± 8 ms; T-peak-to-T-end Total : 110 ± 7 ms vs. 137 ± 10 ms; QTc: 470 ± 12 ms vs. 506 ± 12 ms; all p ≤ .0001) were significantly shorter with CSP. Improved T-peak-to-T-end values were unrelated to pre-implant QRSd or LV function. Interobserver variability was 4.6 ± 1.9 ms. Frontal QRS-T angle narrowing (132°to 104°, p = .001) and QTc shortening (483 ± 13 ms to 464 ± 12 ms, p = .008) were seen only with CSP. Conclusions: In addition to improved depolarization, CSP reduced repolarization heterogeneity and provided greater T-wave memory resolution as compared to BiVP. Both modalities of CSP (HBP + LBAP) resulted in comparably reduced repolarization heterogeneity regardless of baseline QRSd and LV function. These observations may confer lower arrhythmogenic risk and warrant further study.

Beyond biventricular pacing: Exploring the advantages of his‐bundle pacing and left bundle branch pacing in heart failure—A systematic review and meta‐analysis

“…Furthermore, pacing at such sites of reticular arrangement may allow for a larger `` virtual electrode 27 , which may then allow for more rapid delivery of electrical depolarization and significantly shorten the QRS duration 28 . Finally, LBBP and HBP have both been proven to result in more physiologic repolarization as compared to BiVP, with improved QT and T‐peak‐to‐T‐end intervals (a measure of transmural dispersion of repolarization), possibly translating to lower proarrhythmic risk 29 . Thus, LBBP may offer excellent ventricular electrical synchrony, which can be crucial for improving cardiac function and reducing HF symptoms.…”

Cardiac Memory T-wave Inversions Noted with Ventricular Pacing: A Possible Electrocardiographic Marker of Appropriate Conduction System Pacing

“…Finally, a recent study demonstrated that conduction system pacing in comparison to biventricular pacing resulted in improved parameters of repolarization as well as resolution of T-wave memory. 21 …”

Depolarization and repolarization dynamics after His‐bundle pacing: Comparison with right ventricular pacing and native ventricular conduction

“…They reported that left bundle branch area pacing yielded a narrower paced QRS duration, shorter QT and QTc interval, lower QT dispersion, and shorter Tpe than RV septal pacing in the acute phase after pacemaker implantation. Recent studies demonstrated the significant benefits of repolarization parameters on ECG after conduction system pacing compared with those after cardiac resynchronization therapy at a mild‐term assessment period of up to 6 weeks or a median of 42 days following implantation (Gupta & Pavri, 2022 ; Sarkar et al, 2022 ). In contrast to previous studies, we implemented a sufficient follow‐up period of 6 months to reduce the effect of ventricular repolarization instability during the acute phase and elicited a continuous advantage of repolarization stability after HBP in the chronic phase.…”