Assessment of Permanent Selective His Bundle Pacing in Left Ventricular Synchronization Using 3-D Speckle Tracking Echocardiography

Relationship between left ventricular mechanical synchrony and left ventricular systolic function: a CZT-SPECT analysis

BACKGROUND

CZT-SPECT has good agreement in the evaluation of mechanical synchronization compared with conventional SPECT. The aim of this study was to evaluate the correlation between left ventricular mechanical contraction synchrony and left ventricular systolic function by gated myocardial perfusion imaging (GMPI) using cadmium-zine-telluride (CZT) single photon emission computed tomography (SPECT).

METHODS

This retrospective study involved 371 patients (239 males and 132 females, mean age 61.06 ± 11.78 years old) who underwent GMPI at the Nuclear Medicine Department of Shanxi Cardiovascular Hospital from January 2020 to August 2020. Systolic synchrony parameters and left ventricular systolic function parameters were calculated via Emory Cardiac Toolbox, including PP, PSD, PHB, HS, HK, EDV, ESV, and LVEF. Based on LVEF value, patients were divided into the severe reduction group (group 1, 127 cases, EF < 35%), moderate reduction group (group 2, 47 cases, 35% ≤ EF < 45%), mild reduction group (group 3, 50 cases, 45% ≤ EF < 50%) and normal group (group 4, 147 cases, EF ≥ 50%). Differences in PP, PSD, PHB, HS and HK among the four groups were compared using one-way ANOVA. Differences between two groups were compared using LSD-t test. The correlation among functional and mechanical contraction synchrony factors were analyzed using Pearson test.

RESULTS

PP, PSD, PHB, HS and HK were significantly different among the four groups (F = 5.20, 188.72, 202.88, 171.05, 101.36, P < 0.001). Pairwise comparison tests showed significant differences in PSD and PHB in each two groups, and HS and HK in each two groups except for group 2 and 3 (t = 0.28 and 0.39, both P > 0.001). PP was significantly higher in group 1, relative to group 3 (t = 2.43, P < 0.001) and group 4 (t = 3.67, P < 0.001). Pearson correlation analysis revealed that LVEF negatively correlates with PP, PSD, PHB (r = 0.194, - 0.790, - 0.799, all P < 0.001). HS and HK showed positive correlation for LVEF (r = 0.778 and 0.795, P < 0.001), PSD, PHB and ESV were had good positive correlation (r = 0.778, 0.795, P < 0.001), PSD, PHB and EDV had good positive correlation (r = 0.722, 0.732, P < 0.001). However, PP had poor correlation with EDV (r = 0.095, P > 0.001). HS and HK were negatively correlated with EDV and ESV (r =  - 0.700 to - 0.594, P < 0.001).

CONCLUSION

CZT SPECT GMPI provided left ventricular mechanical contraction synchrony parameters that correlated well with left ventricular systolic function. Worse left ventricular mechanical contraction synchrony lead to decreased LVEF, making the systolic synchrony parameters valuable in the prediction of left ventricular systolic function.

Electro-energetics of Biventricular, Septal and Conduction System Pacing

Abnormal electrical activation of the ventricles creates abnormalities in cardiac mechanics. Local contraction patterns, as reflected by strain, are not only out of phase, but also show opposing length changes in early and late activated regions. Consequently, the efficiency of cardiac pump function (the amount of stroke work generated by a unit of oxygen consumed), is approximately 30% lower in dyssynchronous than in synchronous hearts. Maintaining good cardiac efficiency appears important for long-term outcomes. Biventricular, left ventricular septal, His bundle and left bundle branch pacing may minimise the amount of pacing-induced dyssynchrony and efficiency loss when compared to conventional right ventricular pacing. An extensive animal study indicates maintenance of mechanical synchrony and efficiency during left ventricular septal pacing and data from a few clinical studies support the idea that this is also the case for left bundle branch pacing and His bundle pacing. This review discusses electro-mechanics and mechano-energetics under the various paced conditions and provides suggestions for future research.

Hemodynamic Effects of Permanent His Bundle Pacing Compared to Right Ventricular Pacing Assessed by Two-Dimensional Speckle-Tracking Echocardiography

We compared the effects of right ventricular (RVP; n = 26) and His bundle (HBP; n = 24) pacing in patients with atrioventricular conduction disorders and preserved LVEF. Postoperatively (1D), and after six months (6M), the patients underwent global longitudinal strain (GLS) and peak systolic dispersion (PSD) evaluation with 2D speckle-tracking echocardiography, assessment of left atrial volume index (LAVI) and QRS duration (QRSd), and sensing/pacing parameter testing. The RVP threshold was lower than the HBP threshold at 1D (0.65 ± 0.13 vs. 1.05 ± 0.20 V, p < 0.001), and then it remained stable, while the HBP threshold increased at 6M (1.05 ± 0.20 vs. 1.31 ± 0.30 V, p < 0.001). The RVP R-wave was higher than the HBP R-wave at 1D (11.52 ± 2.99 vs. 4.82 ± 1.41 mV, p < 0.001). The RVP R-wave also remained stable, while the HBP R-wave decreased at 6M (4.82 ± 1.41 vs. 4.50 ± 1.09 mV, p < 0.02). RVP QRSd was longer than HBP QRSd at 6M (145.0 ± 11.1 vs. 112.3 ± 9.3 ms, p < 0.001). The absolute value of RVP GLS decreased at 6M (16.32 ± 2.57 vs. 14.03 ± 3.78%, p < 0.001), and HBP GLS remained stable. Simultaneously, RVP PSD increased (72.53 ± 24.15 vs. 88.33 ± 30.51 ms, p < 0.001) and HBP PSD decreased (96.28 ± 33.99 vs. 84.95 ± 28.98 ms, p < 0.001) after 6 months. RVP LAVI increased (26.73 ± 5.7 vs. 28.40 ± 6.4 mL/m², p < 0.05), while HBP LAVI decreased at 6M (30.03 ± 7.8 vs. 28.73 ± 8.7 mL/m², p < 0.01). These results confirm that HBP does not disrupt ventricular synchrony and provides advantages over RVP.

His-Purkinje conduction system pacing: A systematic review and network meta-analysis in bradycardia and conduction disorders

BACKGROUND

His-Purkinje conduction system pacing (HPCSP) has emerged as an effective alternative to overcome the limitations of right ventricular pacing (RVP) via physiological left ventricular activation, but there remains a paucity of comparative information for His bundle pacing (HBP) and left bundle branch pacing (LBBP).

METHODS

A Bayesian random-effects network analysis was conducted to compare the relative effects of HBP, LBBP, and RVP in patients with bradycardia and conduction disorders. PubMed, Embase, Cochrane Library, and Web of Science were systematically searched from database inception until September 21, 2021.

RESULTS

Twenty-eight studies involving 4160 patients were included in this meta-analysis. LBBP significantly improved success rate, pacing threshold, pacing impedance, and R-wave amplitude compared with HBP. LBBP also demonstrated a nonsignificant trend towards superior outcomes of lead complications, heart failure hospitalization, atrial fibrillation, and all-cause death. However, HBP was associated with significantly shorter paced QRS duration relative to LBBP. Despite higher success rates, shorter procedure/fluoroscopy duration, and fewer lead complications, patients receiving RVP were more likely to experience reduced left ventricular ejection fraction, longer paced QRS duration, and higher rates of heart failure hospitalization than those receiving HPCSP. No statistical differences were observed in the remaining outcome measures.

CONCLUSIONS

This network meta-analysis demonstrates the efficacy and safety of HPCSP for the treatment of bradycardia and conduction disorders, with differences in pacing parameters, electrophysiology characteristics, and clinical outcomes between HBP and LBBP. Larger-scale, long-term comparative studies are warranted for further verification.

Assessment of ventricular mechanical synchronization after left bundle branch pacing using 2-D speckle tracking echocardiography

Background

The left bundle branch pacing (LBBP) makes the ventricular depolarization closer to the physiological state and shortens QRS duration. The purpose of this study is to explore the ventricular systolic mechanical synchronization after LBBP in comparison with traditional right ventricular pacing (RVP) using two‐dimensional strain echocardiography (2D‐STE).

Methods

Thirty‐two patients who received LBBP (n = 16) or RVP (n = 16) from October 2018 to October 2019 and met the inclusion criteria were included in this retrospective study. Electrocardiogram (ECG) characteristics, pacing parameters, pacing sites, and safety events were assessed before and after implantation. Acquisition and analysis of ventricular systolic synchronization were implemented using 2D‐STE.

Results

In RVP group, ECG showed left bundle branch block patterns. At LBBP, QRS morphology was in the form of right bundle branch block, and QRS durations were significantly shorter than that of the RVP QRS (109.38 ± 12.89 vs 149.38 \± 19.40 ms, P < .001). Both the maximum time differences (TD) and SDs of the 18‐segments systolic time to peak systolic strain were significantly shorter under LBBP than under RVP (TD, 66.62 ± 37.2 vs 148.62 ± 43.67 ms, P < .01; SD, 21.80 ± 12.13 vs 52.70 ± 17.72 ms, P < .01), indicating that LBBP could provide better left ventricular mechanical synchronization. Left and right ventricular pre‐ejection period difference was significantly longer in RVP group than in LBBP group (10.23 ± 3.07 vs 39.94 ± 14.81 ms, P < .05), indicating left and right ventricular contraction synchronization in LBBP group being better than in RVP group.

Conclusion

LBBP is able to provide a physiologic ventricular activation pattern, which results in ventricular mechanical contraction synchronization.

[Echocardiographic assessment of myocardial function during His bundle and right ventricular pacing]

INTRODUCTION

In patients with pacemaker (PM) therapy, His bundle stimulation (HBS) may lead to a more synchronous activation of the left ventricle (LV) than conventional right ventricular stimulation (RVS). In this study, we investigated to which extent this effect can be objectified by means of contemporary echocardiographic functional imaging.

METHODS

In all, 15 RVS patients (6 women, mean age 76.6 ± 4.1 years) and 15 HBS patients (6 women, mean age 74.6 ± 3.7 years) underwent echocardiography with and without cardiac pacing. Besides LV end-diastolic volume (EDV), ejection fraction (EF), and global strain (GLS), we measured global and regional myocardial work and LV efficiency based on noninvasive pressure-strain loops.

RESULTS

In all HBS patients, optimization of PM settings resulted in immediate changes in myocardial function parameters. With pacing, RVS patients showed a higher decrease in EF and GLS than HBS patients. Global LV work and LV work efficiency decreased significantly only in RVS patients.

CONCLUSION

Changes in regional and global myocardial function can by proven and quantified by functional echocardiography. In patients under PM therapy, HBS shows functional advantages in comparison to conventional RVS.