Improved all-cause mortality with left bundle branch area pacing compared to biventricular pacing in cardiac resynchronization therapy: a meta-analysis

Vectorcardiography in CRT: What We Know and What There Is to Learn

Vectorcardiography (VCG) is an electrophysiological investigation technique, giving supplementary information about the electrical activation of the heart, compared to traditional 12-lead electrocardiography (ECG). Whereas the 12-lead ECG has found its way into global clinical cardiology practice in numerous cardiac pathophysiological instances, VCG has not. In an investigation of the electrical activation of the heart in cardiac resynchronization therapy (CRT), in order to understand the baseline pathology in potentially eligible patients, and to understand and optimize CRT-derived paced activation of the heart in the therapy's recipients, all of these aspects are essential to the success of the therapy. Due to a consistently present group of non-responders in CRT, VCG has gained interest as a potential improvement in this field. This review comprehensively summarizes the contemporary evidence for the additional value of VCG in CRT, as well as current deficiencies in evidence, to support its implementation in global practice in addition to, or as a substitution for, traditional 12-lead ECG.

Clinical Response to Resynchronization Therapy: Conduction System Pacing vs Biventricular Pacing. CONSYST-CRT trial

BACKGROUND

Randomized studies comparing conduction system pacing (CSP) with biventricular pacing (BiVP) are scarce and do not include clinical outcomes.

OBJECTIVES

The CONSYST-CRT (Conduction System Pacing vs Biventricular Resynchronization Therapy in Systolic Dysfunction and Wide QRS) trial aimed to test the noninferiority of CSP as compared with BiVP in patients with an indication for cardiac resynchronization therapy, with respect to a combined clinical endpoint at 1-year follow-up.

METHODS

CONSYST-CRT is a randomized, controlled, noninferiority trial (NCT05187611). One hundred thirty-four patients with cardiac resynchronization therapy indication were randomized to BiVP or CSP and followed up for 12 months. Crossover was allowed when the primary allocation procedure failed. The atrioventricular interval was optimized to obtain fusion with intrinsic conduction. The primary combined endpoint was all-cause mortality, cardiac transplant, heart failure hospitalization, or left ventricular ejection fraction (LVEF) improvement <5 points at 12 months. Secondary endpoints were LVEF increase, LV end-systolic volume (LVESV) decrease, echocardiographic response (≥15% LVESV decrease), QRS shortening, septal flash correction, NYHA functional class improvement, and a combined endpoint of all-cause mortality, cardiac transplantation, and heart failure hospitalization.

RESULTS

Sixty-seven patients were allocated to each group. Eighteen patients (26.9%) crossed from CSP to BiVP; 5 (7.5%) crossed over from BiVP to CSP. Noninferiority (NI) was observed for CSP compared with BiVP for the primary endpoint (23.9% vs 29.8%, respectively; mean difference -5.9; 95% CI: -21.1 to 9.2; P = 0.02) and for the combined endpoint of all-cause mortality, cardiac transplantation, and heart failure hospitalization (11.9% vs 17.9%; P < 0.01 NI); echocardiographic response (66.6% vs 59.7%; P = 0.03 NI); NYHA functional class (P < 0.001 NI); and QRS shortening (P < 0.01). LVEF, LVESV, and septal flash endpoint values were similar, but noninferiority was not met (14.1 ± 10% vs 14.4 ± 10%, -27.9 ± 27% vs -27.9 ± 28%, -2.2 ± 2.7 mm vs -2.7 ± 2.4 mm, respectively).

CONCLUSIONS

CSP was noninferior to BiVP in achieving clinical and echocardiographic response, suggesting that CSP could be an alternative to BiVP. (Conduction System Pacing vs Biventricular Resynchronization Therapy in Systolic Dysfunction and Wide QRS [CONSYST-CRT]; NCT05187611).

Hierarchical physiologic pacing to enhance clinical outcomes in conduction system pacing

BACKGROUND

Left bundle branch area pacing (LBBAP) includes left bundle branch pacing (LBBP) (truncal or fascicular) and left ventricular septal pacing (LVSP). Studies show that LBBP provides better outcomes than LVSP in heart failure.

OBJECTIVES

We classified the lead placement with computed tomographic angiography (CTA) based method (CARA-Metis; CARA Medical Ltd) into LBBP or LVSP and assessed the effect of pacing lead location relative to the conduction tree hierarchy and the LV endocardium on clinical outcomes in patients with successful LBBAP.

METHODS

Two-center, nonrandomized, observational study that included patients with LBBAP undergoing CTA. The CTA parameters analyzed (1) the distance between the lead tip and the anterior position of the floor of the membranous septum (LH) and (2) the distance between the lead tip and LV endocardium (LE).

RESULTS

Among 264 patients analyzed, 172 (65%) with interpretable CTAs were included. Pacing lead tip was categorized as LBBP in 153 (89%) and LVSP in 19 patients (11%) (median values were 27.7 mm [interquartile range, 9.21] for LH and 0.80 mm [interquartile range, 2.59] for LE). Shorter LH was associated with greater improvement in left ventricular ejection fraction (LVEF) [each 1 mm shorter LH increased LVEF by 0.25% when adjusted for baseline LVEF (P = 0.00637)]. Closer to the LV endocardium (larger LE), increased LVEF response by 0.63% for each additional 1 mm (P = 0.0133) in the entire cohort. Patients with depressed LVEF accrued significantly larger improvement in LVEF (P < 0.0001 for both).

CONCLUSION

Hierarchical physiologic pacing with improved LVEF response is achieved with a closer position of the pacing lead to the His bundle and the LV endocardium.

Early Improvement in Cardiac Function and Dyssynchrony After Physiological Upgrading in Pacing-Induced Cardiomyopathy

BACKGROUND

Interventricular dyssynchrony derived from the classic non-physiological stimulation (n-PS) of the right ventricle (RV) is a known cause of left ventricular dysfunction (LVDys).

METHODS

This was a prospective descriptive single-center study. We analyzed patients who develop LVDys with n-PS, and the results after upgrading to conduction system pacing (CSP). Ultra-high frequency electrocardiogram (UHF-ECG) was performed pre and post-implantation of the last patients included. ECG recordings in 16 frequency bands (150-1000 Hz) were used to create maps of ventricular depolarization. The maximum time difference between the centers of mass of the complex UHF QRS of leads V1-V6 (electrical dyssynchrony [DYS-e] 16) and V1-V8 (DYS-e 18) defined ventricular dyssynchrony. Data were expressed as mean ± standard deviation.

RESULTS

27 patients were upgraded to CSP from January 2022 to January 2024 after developing LVDys. Permanent His bundle pacing (p-HBP) was achieved in 63% (n = 17); in the other 10 patients left bundle branch area pacing (LBBAp) was performed. The average baseline LVEF improved from 34.5% (27-42) to 47.6% (38.2-57), p < 0.001. Telediastolic left ventricle diameter as well as QRS width also decreased. Thresholds remained stable at 6-month follow-up. The last eight patients included were studied in terms of ventricular synchrony parameters by UHF-ECG (VDI Technologies), both His bundle pacing (HBP) and the LBBAp achieved significant improvement with respect to baseline parameters.

CONCLUSIONS

LVEF improved in patients with previous n-PS-induced cardiomyopathy after upgrading to CSP. LVDys due to dyssynchronopathy is frequent and probably underdiagnosed. UHF-ECG provides useful new information about ventricular activation and will likely improve patient selection for cardiac resynchronization therapy (CRT).

Is Conduction System Pacing Going to Be the New Gold Standard for Cardiac Resynchronization Therapy?

The current gold standard in device therapy for advanced heart failure (HF), which has been firmly established in HF management for more than 25 years, is classical biventricular pacing (BiV-CRT). In the last decade, a new pacing modality called conduction system pacing (CSP) has emerged as a variant for advanced cardiac device therapy. It provides pacing with preserved intrinsic cardiac activation by direct stimulation of the specific cardiac conduction system. The term CSP integrates the modalities of HIS bundle pacing (HBP) and left bundle branch area pacing (LBBAP), both of which have provided convincing data in smaller randomized and big non-randomized studies for the prevention of pacemaker-induced cardiomyopathy and for providing effective cardiac resynchronization therapy in patients with classical CRT-indication (primary approach or after failed CRT). Recent American guidelines proposed the term "cardiac physiological pacing" (CPP), which summarizes CSP including left ventricular septal pacing (LVSP), a technical variant of LBBAP together with classical BiV-CRT. The terms HOT-CRT (HIS-optimized CRT) and LOT-CRT (LBBP-optimized CRT) describe hybrid technologies that combine CSP with an additional coronary-sinus electrode, which is sometimes useful in patients with advanced HF and diffuse interventricular conduction delay. If CSP continues providing promising data that can be confirmed in big, randomized trials, it is likely to become the new gold standard for patients with an expected high percentage of pacing (>20%), possibly also for cardiac resynchronization therapy. CSP is a sophisticated new treatment option that has the potential to raise the term "cardiac resynchronization therapy" to a new level. The aim of this review is to provide basic technical, anatomical, and functional knowledge of these new pacemaker techniques in order to facilitate the understanding of the different modalities, as well as to provide an up-to-date overview of the existing randomized and non-randomized evidence, particularly in direct comparison to right ventricular and classical biventricular pacing.

Sex Differences in Left Bundle Branch Area Pacing Versus Biventricular Pacing for Cardiac Resynchronization Therapy

BACKGROUND

Women respond more favorably to biventricular pacing (BIVP) than men. Sex differences in atrioventricular and interventricular conduction have been described in BIVP studies. Left bundle branch area pacing (LBBAP) offers advantages due to direct capture of the conduction system. We hypothesized that men could respond better to LBBAP than BIVP.

OBJECTIVES

This study aims to describe the sex differences in response to LBBAP vs BIVP as the initial cardiac resynchronization therapy (CRT).

METHODS

In this multicenter prospective registry, we included patients with left ventricular ejection fraction ≤35% and left bundle branch block or a left ventricular ejection fraction ≤40% with an expected right ventricular pacing exceeding 40% undergoing initial CRT with LBBAP or BIVP. The composite primary outcome was heart failure-related hospitalization and all-cause mortality. The primary safety outcome included all procedure-related complications.

RESULTS

There was no significant difference in the primary outcome when comparing men and women receiving LBBAP (P = 0.46), whereas the primary outcome was less frequent in women in the BIVP group than men treated with BIVP (P = 0.03). The primary outcome occurred less frequently in men undergoing LBBAP (29.9%) compared to those treated with BIVP (46.5%) (P = 0.004). In women, the incidence of the primary endpoint was 24.14% in the LBBAP group and 36.2% in the BIVP group; however, this difference was not statistically significant (P = 0.23). Complication rates remained consistent across all groups.

CONCLUSIONS

Men and women undergoing LBBAP for CRT had similar clinical outcomes. Men undergoing LBBAP showed a lower risk of heart failure-related hospitalizations and all-cause mortality compared to men undergoing BIVP, whereas there was no difference between LBBAP and BIVP in women.