Left Bundle Branch Block-induced Cardiomyopathy: Insights From Left Bundle Branch Pacing

Comparison of electrocardiogram parameters and echocardiographic response between distinct left bundle branch area pacing modes in heart failure patients

Background

Left bundle branch area pacing (LBBAP) has become an alternative method for cardiac resynchronization therapy. Various modes of LBBAP have been determined, including left bundle trunk pacing (LBTP), left anterior branch pacing (LAFP) and left posterior branch pacing (LPFP). However, whether the outcomes of various pacing modes differ in heart failure (HF) patients is still unclear. This study aimed to compare the electrophysiological characteristics and echocardiographic response rate among those distinct modes of LBBAP.

Methods

HF patients undergoing successful LBBAP were retrospectively included. Distinct modes of pacing were determined based on paced QRS morphology. The fluoroscopic images were collected to compare the lead tip position between the groups. The electrocardiograms (ECG) before and after LBBAP were used to measure the depolarization (QRS duration [QRSd] and the interventricular delay [IVD]), and the repolarization parameters [QTc, TpeakTend(TpTe), and TpTe/QTc]. The left ventricular ejection fraction (LVEF) and left ventricular end-diastolic diameter (LVEDD) of patients were also recorded. In addition, the lead parameters and certain complications were compared.

Results

A total of 64 HF patients were finally included, consisting of 16 (25.0%) patients in the LBTP group, 22 (34.4%) patients in the LAFP group, and 26 (40.6%) patients in the LPFP group. The distribution features of LBBAP lead tips were significantly related to pacing modes: LBTP was more likely to be in zone 4 while LAFP or LPFP was prone to locate in zone 5. After LBBAP, the ventricular ECG parameters were significantly improved, regardless of pacing modes. Besides, the LVEF of the patients was significantly increased (P < 0.001), and LVEDD was significantly decreased (P < 0.001). There was no difference in the response rate and super-response rate among groups (P > 0.05). In addition, the lead parameters remained stable and no significant difference was observed among groups.

Conclusion

LPFP was the main pacing mode among HF patients after LBBAP. The paced QRS morphology was significantly related to the position of lead tips. After LBBAP, the ventricular depolarization synchronization and repolarization stability were both significantly improved, regardless of pacing modes. There was no significant difference in the echocardiographic response rate among distinct LBBAP modes.

Retrograde Conduction in Left Bundle Branch Block: Insights From Left Bundle Branch Pacing

BACKGROUND

Biventricular pacing is a well-established therapy for patients with heart failure (HF), left bundle branch block (LBBB) and left ventricular (LV) dysfunction. Left bundle branch pacing (LBBP) has emerged as an alternative to biventricular pacing.

OBJECTIVES

The aim of this study was to assess the retrograde conduction properties of the left bundle branch in patients with nonischemic cardiomyopathy and LBBB during LBBP and its clinical implications.

METHODS

Patients undergoing successful LBBP for nonischemic cardiomyopathy with LV ejection fraction (LVEF) ≤35% and LBBB were included. Continuous recording of His potential was performed using a quadripolar catheter. Unidirectional block was defined as retrograde His bundle activation during LBBP with stimulus to His potential (SH) duration less than or equal to antegrade HV interval and bidirectional block as VH dissociation or SH duration greater than HV interval. HF hospitalization, ventricular arrhythmias, and mortality were documented.

RESULTS

A total of 165 patients were included. The mean follow-up duration was 21.8 ± 13.1 months. Bidirectional block (group I) was observed in 82% (n = 136), and these patients were noted to have advanced HF stage and prolonged baseline QRS duration. Unidirectional block (group II) with intact retrograde conduction was observed in 18% (n = 29) and was associated with narrow paced QRS duration and higher LVEF during follow-up. Super-response (LVEF ≥50%) was observed in 54.4% (n = 74) in group I compared with 73.3% (n = 22) in group II (P = 0.03). The OR for LVEF normalization was 4.1 (95% CI: 1.26-13.97; P = 0.02), with unidirectional block compared with bidirectional block in patients with LBBB and LV dysfunction. Adverse clinical outcomes as measured by a composite of HF hospitalization, ventricular arrhythmias, and mortality were significantly higher in group I compared with group II (12.5% vs 0%; P = 0.04).

CONCLUSIONS

Bidirectional block in LBBB was characterized by advanced HF symptoms, while unidirectional block was associated with better clinical outcomes after cardiac resynchronization therapy by LBBP.

Left bundle branch block cardiomyopathy (LBBB-CMP): from the not-so-benign finding of idiopathic LBBB to LBBB-CMP diagnosis and treatment

Introduction Idiopathic left bundle branch block (iLBBB) is an uncommon finding. Its benignity has been increasingly questioned, though its natural history remains poorly clarified. Similarly, LBBB-cardiomyopathy (LBBB-CM) has been also increasingly recognized as a distinct entity, where electromechanical dyssynchrony seems to play a central role in left ventricular dysfunction (LVD) development. Still, it remains a scarcely studied topic. There is an urgent need for investigation and evidence reinforcement in these areas.

OBJECTIVES

two main objectives: (1) to explore the natural history of "asymptomatic" iLBBB carriers; (2) to characterize the outcomes and therapeutic approach used in a "real-world" cohort of possible LBBB-CMP patients (pts).

METHODS

tertiary care centre retrospective study of pts with iLBBB and possible LBBB-CMP, screened from a large hospital electrocardiographic database from 2011 to 2017 (LBBB = 347). To assign the 1st objective, only pts with left ventricular ejection fraction (LVEF) ≥ 50% and available follow-up (FU) data were included (n = 152). Regarding the 2nd objective, possible LBBB-CMP pts were selected and defined as iLBBB pts with LVD (LVEF < 50%) and no secondary causes for LVD (n = 53). Data were based on pts' careful review of medical records.

RESULTS

focusing our 1st objective, 152 iLBBB carriers were identified. Median FU time were 8 years, and 61% were female. During FU, approximately 25% developed LVD, 20% needed ≥ 1 cardiovascular (CV) hospitalization, and 15% needed a cardiac device implantation. The majority (2/3) of pts with LVD on FU (n = 35) had no secondary causes for LVD, being classified as possible LBBB-CMP pts. Time-to-LVD analysis showed no differences between pts with a known cause for LVD vs LBBB-CMP pts (Log-rank = 0.713). Concerning the 2nd objective, 53 possible LBBB-CMP pts were identified. Median FU time were 10 years, and 51% were female. During the FU, 77% presented heart failure (HF) symptoms, and 42% needed ≥ 1 CV hospitalization, mainly due to HF. Half presented severe LVD at some point in time, and 55% needed a cardiac device, most of them a cardiac resynchronization therapy (CRT) device. Comparing CRT with non-CRT pts, no differences were found in terms of medical therapy, but better outcomes were observed in CRT group: LVEF improvement was higher (median LVEF improvement of 11% in non-CRT vs 27% in CRT; p < 0.001), and fully recovery from LVD was more frequent (50% of CRT vs 14% non-CRT; p = 0.028).

CONCLUSION

our data strengthen current evidence on natural history of iLBBB, showing significant CV morbidity associated with the presence of iLBBB, and reinforces the need for a serial and proper FU of these carriers. Our data on "real-world" possible LBBB-CMP pts shows high rates of CV events, namely HF-related events, and supports the growing evidence pointing out CRT as this subgroup of pts' cornerstone of treatment. In conclusion, our work sheds additional light on these largely unknown topics and underlines the urgent need for larger and prospective studies addressing the identification of LVD development predictors in iLBBB carriers, as well as the establishment of diagnostic criteria and therapeutic approach for LBBB-CMP.

Tpeak-Tend ECG Marker in Obesity and Cardiovascular Diseases: A Comprehensive Review

Globally, cardiovascular diseases are still the leading cause of death. Numerous methods are used to diagnose cardiovascular pathologies; there is still a place for straightforward and noninvasive techniques, such as electrocardiogram (ECG). Depolarization and repolarization parameters, including QT interval and its derivatives, are well studied. However, the Tpeak-Tend interval is a novel and promising ECG marker with growing evidence for its potential role in predicting malignant arrhythmias. In this review, we discuss the association between the Tpeak-Tend interval and several cardiovascular diseases, including long QT syndrome, cardiomyopathies, heart failure, myocardial infarction, and obesity, which constitutes one of the risk factors for cardiovascular diseases.

Successful prediction of left bundle branch block-induced cardiomyopathy and treatment effect by artificial intelligence-enabled electrocardiogram

BACKGROUND

Left bundle branch block (LBBB) induced cardiomyopathy is an increasingly recognized disease entity.  However, no clinical testing has been shown to be able to predict such an occurrence.

CASE REPORT

A 70-year-old male with a prior history of LBBB with preserved ejection fraction (EF) and no other known cardiovascular conditions presented with presyncope, high-grade AV block, and heart failure with reduced EF (36%). His coronary angiogram was negative for any obstructive disease. No other known etiologies for cardiomyopathy were identified. Artificial intelligence-enabled ECGs performed 6 years prior to clinical presentation consistently predicted a high probability (up to 91%) of low EF. The patient successfully underwent left bundle branch area (LBBA) pacing with correction of the underlying LBBB. Subsequent AI ECGs showed a large drop in the probability of low EF immediately after LBBA pacing to 47% and then to 3% 2 months post procedure. His heart failure symptoms markedly improved and EF normalized to 54% at the same time.

CONCLUSIONS

Artificial intelligence-enabled ECGS may help identify patients who are at risk of developing LBBB-induced cardiomyopathy and predict the response to LBBA pacing.

Left bundle branch block-induced dilated cardiomyopathy: Definitions, pathophysiology, and therapy

Left bundle branch block (LBBB) is a frequent finding in patients with heart failure (HF), particularly in those with dilated cardiomyopathy (DCM). LBBB has been commonly described as a consequence of DCM development. However, a total recovery of left ventricular (LV) function after cardiac resynchronization therapy (CRT), observed in patients with LBBB and DCM, has led to increasing acknowledgement of LBBB-induced dilated cardiomyopathy (LBBB-iDCM) as a specific pathological entity. Its recognition has important clinical implications, as LBBB-iDCM patients may benefit from an early CRT strategy rather than medical HF therapy only. At present, there are no definitive diagnostic criteria enabling the universal identification of LBBB-iDCM, and no defined therapeutic approach in this subgroup of patients. This review compiles the main findings about LBBB-iDCM pathophysiology and the current proposed diagnostic criteria and therapeutic approach.

Abnormal conduction-induced cardiomyopathy: a poorly explored entity

A dyssynchronous biventricular activation, which can be determined by left bundle branch block, chronic right ventricular pacing, frequent premature ventricular complexes, or pre-excitation, can cause a global abnormal contractility, thus leading to systolic dysfunction and left ventricular remodelling in a unique nosological entities: abnormal conduction-induced cardiomyopathies. In this clinical scenario, the mainstay therapy is eliminating or improving LV dyssynchrony, removing the trigger. This usually ensures the improvement and even recovery of cardiac geometry and left ventricular function, especially in the absence of genetic background. A multidisciplinary approach, integrating advanced multimodal imaging, is essential for the systematic aetiological definition and the subsequent evaluation and aetiology-guided therapies of patients and their families. This review aims to describe mechanisms, prevalence, risk factors, and diagnostic and therapeutic approach to the various abnormal conduction-induced cardiomyopathies, starting from reasonable certainties and then analysing the grey areas requiring further studies.

Nonischemic or Dual Cardiomyopathy in Patients With Coronary Artery Disease

BACKGROUND

Randomized trials in obstructive coronary artery disease (CAD) have largely shown no prognostic benefit from coronary revascularization. Although there are several potential reasons for the lack of benefit, an underexplored possible reason is the presence of coincidental nonischemic cardiomyopathy (NICM). We investigated the prevalence and prognostic significance of NICM in patients with CAD (CAD-NICM).

METHODS

We conducted a registry study of consecutive patients with obstructive CAD on coronary angiography who underwent contrast-enhanced cardiovascular magnetic resonance imaging for the assessment of ventricular function and scar at 4 hospitals from 2004 to 2020. We identified the presence and cause of cardiomyopathy using cardiovascular magnetic resonance imaging and coronary angiography data, blinded to clinical outcomes. The primary outcome was a composite of all-cause death or heart failure hospitalization, and secondary outcomes were all-cause death, heart failure hospitalization, and cardiovascular death.

RESULTS

Among 3023 patients (median age, 66 years; 76% men), 18.2% had no cardiomyopathy, 64.8% had ischemic cardiomyopathy (CAD+ICM), 9.3% had CAD+NICM, and 7.7% had dual cardiomyopathy (CAD+dualCM), defined as both ICM and NICM. Thus, 16.9% had CAD+NICM or dualCM. During a median follow-up of 4.8 years (interquartile range, 2.9, 7.6), 1116 patients experienced the primary outcome. In Cox multivariable analysis, CAD+NICM or dualCM was independently associated with a higher risk of the primary outcome compared with CAD+ICM (adjusted hazard ratio, 1.23 [95% CI, 1.06-1.43]; P=0.007) after adjustment for potential confounders. The risks of the secondary outcomes of all-cause death and heart failure hospitalization were also higher with CAD+NICM or dualCM (hazard ratio, 1.21 [95% CI, 1.02-1.43]; P=0.032; and hazard ratio, 1.37 [95% CI, 1.11-1.69]; P=0.003, respectively), whereas the risk of cardiovascular death did not differ from that of CAD+ICM (hazard ratio, 1.15 [95% CI, 0.89-1.48]; P=0.28).

CONCLUSIONS

In patients with CAD referred for clinical cardiovascular magnetic resonance imaging, NICM or dualCM was identified in 1 of every 6 patients and was associated with worse long-term outcomes compared with ICM. In patients with obstructive CAD, coincidental NICM or dualCM may contribute to the lack of prognostic benefit from coronary revascularization.

Effectiveness of conduction system pacing for cardiac resynchronization therapy: A systematic review and network meta-analysis

INTRODUCTION

Cardiac resynchronization therapy (CRT) with biventricular pacing (BiV-CRT) is ineffective in approximately one-third of patients. CRT with Conduction system pacing (CSP-CRT) may achieve greater synchronization. We aimed to assess the effectiveness of CRT with His pacing (His-CRT) or left bundle branch pacing (LBB-CRT) in lieu of biventricular CRT.

METHODS AND RESULTS

The PubMed, Embase, Web of Science, Scopus, and the Cochrane Library were systematically searched until August 19, 2023, for original studies including patients with reduced left ventricular ejection fraction (LVEF) who received His- or LBB-CRT, that reported either CSP-CRT success, LVEF, QRS duration (QRSd), or New York Heart Association (NYHA) classification. Effect measures were compared with frequentist network meta-analysis. Thirty-seven publications, including 20 comparative studies, were included. Success rates were 73.5% (95% CI: 61.2-83.0) for His-CRT and 91.5% (95% CI: 88.0-94.1) for LBB-CRT. Compared to BiV-CRT, greater improvements were observed for LVEF (mean difference [MD] for His-CRT +3.4%; 95% CI [1.0; 5.7], and LBB-CRT: +4.4%; [2.5; 6.2]), LV end-systolic volume (His-CRT:17.2mL [29.7; 4.8]; LBB-CRT:15.3mL [28.3; 2.2]), QRSd (His-CRT: -17.1ms [-25.0; -9.2]; LBB-CRT: -17.4ms [-23.2; -11.6]), and NYHA (Standardized MD [SMD]: His-CRT:0.4 [0.8; 0.1]; LBB-CRT:0.4 [-0.7; -0.2]). Pacing thresholds at baseline and follow-up were significantly lower with LBB-CRT versus both His-CRT and BiV-CRT. CSP-CRT was associated with reduced mortality (R = 0.75 [0.61-0.91]) and hospitalizations risk (RR = 0.63 [0.42-0.96]).

CONCLUSION

This study found that CSP-CRT is associated with greater improvements in QRSd, echocardiographic, and clinical response. LBB-CRT was associated with lower pacing thresholds. Future randomized trials are needed to determine CSP-CRT efficacy.

Left Bundle Branch Pacing for Heart Failure and Left Bundle Branch Block Patients With Mildly Reduced and Preserved Left Ventricular Ejection Fraction

BACKGROUND

Left bundle branch block (LBBB) may induce or aggravate heart failure (HF). Few data are available on patients with HF and LBBB with mildly reduced ejection fraction (HFmrEF; left ventricular ejection fraction [LVEF] 40%-50%) and those with preserved EF (HFpEF. LVEF ≥ 50%). We aimed to assess the long-term outcomes of left bundle branch pacing (LBBP) on cardiac function and remodelling in patients with LBBB and symptomatic HFmrEF and HFpEF.

METHODS

Nonischemic cardiomyopathy (NICM) patients with HFmrEF and HFpEF (LVEF from 40% to 60% as defined with the use of echocardiography) with LBBB who successfully underwent LBBP (n = 50) were prospectively included from 4 centres. Patient characteristics and echocardiographic and lead parameters were recorded at implantation and during follow-ups of 1, 3, 6, and 12 months.

RESULTS

All patients completed 1-year follow up. The LVEF was significantly improved from 46.5 ± 5.2% at baseline to 60.0 ± 6.1% (n = 50; P < 0.001) after 1-year follow up. Higher ΔLVEF and super-response rate were observed in the HFmrEF group (n = 30) than in the HFpEF group (n = 20).

CONCLUSIONS

LBBP improved symptoms and reversed remodelling in patients with LBBB and symptomatic HF at 1-year follow-up. Improvement occurred even in HFpEF patients, and the resynchronisation effect was better in HFmrEF group.

Early left bundle branch pacing in heart failure with mildly reduced ejection fraction and left bundle branch block

BACKGROUND

Left bundle branch pacing (LBBP) achieves resynchrony and improves cardiac function in heart failure (HF) patients with reduced ejection fraction (EF) by correcting left bundle branch block (LBBB). Few data on the efficacy of early LBBP in HF with mildly reduced EF (HFmrEF) and LBBB have been reported.

OBJECTIVE

The purpose of this study was to explore the efficacy of early LBBP in patients with HFmrEF and LBBB.

METHODS

Consecutive patients with HFmrEF (left ventricular EF [LVEF] 35%-50%) and LBBB were prospectively enrolled to receive LBBP (Early-LBBP group) plus guideline-directed medical therapy (GDMT) or GDMT alone (GDMT group). Study outcomes included changes in LVEF, LV end-diastolic diameter (LVEDD), New York Heart Association (NYHA) functional classification, and N-terminal pro-brain natriuretic peptide (NT-proBNP), and clinical events (HF rehospitalization or syncope). Subgroup analysis compared efficacy of LBBP between patients with LBBB only without comorbidities or late gadolinium enhancement (LGE) (LBBB-Only group) and patients with either comorbidities or LGE (LBBB-Combined group).

RESULTS

Fifty-four patients were enrolled and analyzed (37 Early-LBBP group; 15 GDMT group). LBBP achieved greater improvement in LVEF (+14.75% ± 7.37% vs -2.42% ± 2.84%; P <.001), reduction of LVEDD (-7.51 ± 5.40 mm vs -0.87 ± 4.36 mm; P <.001) and NYHA classification (-0.84 ± 0.76 vs -0.13 ± 0.74; P = .004), and similar reduction of NT-proBNP (-408.83 ± 920.29 pg/mL vs -229.05 ± 1579.17 pg/mL; P = .610) at 6 months. Early LBBP showed significantly reduced clinical events (0.0% vs 40.0%; P <.001) after 20.68 ± 13.55 months of follow-up. Subgroup analysis showed patients in the LBBB-Only group benefited more from LBBP with regard to LVEF improvement and LVEDD reduction than the LBBB-Combined group.

CONCLUSION

Early LBBP with GDMT demonstrated greater improvement of cardiac function and reduced clinical events than GDMT alone in patients with HFmrEF and LBBB.

2023 HRS/APHRS/LAHRS guideline on cardiac physiologic pacing for the avoidance and mitigation of heart failure

Cardiac physiologic pacing (CPP), encompassing cardiac resynchronization therapy (CRT) and conduction system pacing (CSP), has emerged as a pacing therapy strategy that may mitigate or prevent the development of heart failure (HF) in patients with ventricular dyssynchrony or pacing-induced cardiomyopathy. This clinical practice guideline is intended to provide guidance on indications for CRT for HF therapy and CPP in patients with pacemaker indications or HF, patient selection, pre-procedure evaluation and preparation, implant procedure management, follow-up evaluation and optimization of CPP response, and use in pediatric populations. Gaps in knowledge, pointing to new directions for future research, are also identified.

2023 HRS/APHRS/LAHRS guideline on cardiac physiologic pacing for the avoidance and mitigation of heart failure

Cardiac physiologic pacing (CPP), encompassing cardiac resynchronization therapy (CRT) and conduction system pacing (CSP), has emerged as a pacing therapy strategy that may mitigate or prevent the development of heart failure (HF) in patients with ventricular dyssynchrony or pacing-induced cardiomyopathy. This clinical practice guideline is intended to provide guidance on indications for CRT for HF therapy and CPP in patients with pacemaker indications or HF, patient selection, pre-procedure evaluation and preparation, implant procedure management, follow-up evaluation and optimization of CPP response, and use in pediatric populations. Gaps in knowledge, pointing to new directions for future research, are also identified.

Comparison of electrocardiographic parameters between left bundle optimized cardiac resynchronization therapy (LOT-CRT) and left bundle branch pacing-cardiac resynchronization therapy (LBBP-CRT)

BACKGROUND

In patients undergoing cardiac resynchronization therapy using left bundle branch area pacing (LBBP-CRT), the addition of a coronary sinus lead, that is, Left bundle optimized CRT (LOT-CRT) might confer additional benefits.

OBJECTIVES

To compare the electrocardiographic characteristics between LBBP-CRT and LOT-CRT MATERIALS AND METHODS: Patients with non-ischemic cardiomyopathy (NICMP) and left bundle branch block (LBBB) with left ventricular ejection fraction <35% who underwent implantation of an atrial lead, a left bundle lead, and a coronary sinus lead were included in this prospective study. Digital 12-lead electrocardiograms were recorded in three pacing modes-AAI, DDD with pacing from the LBB lead (LBBP-CRT), and DDD with pacing from both left bundle and coronary sinus leads (LOT-CRT). QRS duration (QRSd), QRS area, QT interval, and T peak-T end (TpTe) intervals were compared.

RESULTS

Among 24 patients, QRSd reduced from 167 ± 21.2 ms to 134.5 ± 23.6 ms with LBBP-CRT (p < .001) and 129.5 ± 18.6 ms with LOT-CRT (p < .001) without a significant difference between LBBP-CRT and LOT-CRT (p = .15). Patients with QRS duration with LBBP-CRT > 131 ms showed a significant reduction in QRSd with LOT-CRT (p = .03). QT interval was reduced with both modes of CRT. LOT-CRT was associated with a greater reduction in QRS area (p = .001), TpTe interval (p = .03), and TpTe/QT ratio (p = .013) compared to LBBP-CRT.

CONCLUSIONS

In patients with NICMP and LBBB, there was no significant difference in QRSd with LOT-CRT compared to LBBP-CRT. However, in patients with QRSd > 131 ms after LBBP-CRT, LOT-CRT resulted in a significantly narrower QRS.

Reverse of left ventricular remodeling in heart failure patients with left bundle branch area pacing: Systematic review and meta-analysis

BACKGROUND

Left bundle branch area pacing (LBBAP) has recently become a promising option for the near-natural restoration of electrical activation. However, the clinical relevance of therapeutic effects in individuals with heart failure with reduced ejection fraction (HFrEF) and dyssynchrony remains unknown.

METHODS

MEDLINE, EMBASE, and Cochrane databases were searched from inception until June 2022. Data from each study was combined using a random-effects model, the generic inverse variance method of DerSimonian and Laird, to calculate standard mean differences and pooled incidence ratio, with 95% confidence intervals (CIs).

RESULTS

A total of 772 HFrEF patients were analyzed from 15 observational studies per protocol. The success rate of LBBAP implantation was 94.8% (95% CI 89.9-99.6, I2 = 79.4%), which was strongly correlated with shortening QRS duration after LBBAP implantation, with a mean difference of -48.10 ms (95% CI -60.16 to -36.05, I2 = 96.7%). Over a period of 6-12 months of follow-up, pacing parameters were stable over time. There were significant improvements in left ventricular ejection fraction (LVEF), left ventricular end-systolic volume (LVESV), left ventricular end-diastolic diameter (LVEDD), and left ventricular end-diastolic volume (LVEDV) with mean difference of 16.38% (95% CI 13.13-19.63, I2 = 90.2%), -46.23 ml (95% CI -63.17 to -29.29, I2 = 86.82%), -7.21 mm (95% CI -9.71 to -4.71, I2 = 84.6%), and -44.52 ml (95% CI -64.40 to -24.64, I2 = 85.9%), respectively.

CONCLUSIONS

LBBAP was associated with improvements in both cardiac function and electrical synchrony. The benefits of LBBAP in individuals with HFrEF and dyssynchrony should be further validated by randomized studies.

MAgnetic resonance imaging based DUal lead cardiac Resynchronization therapy: A prospectIve Left Bundle Branch Pacing Study (MADURAI LBBP study)

BACKGROUND

Cardiac resynchronization therapy(CRT) is a class-I indication for LVEF≤35%, and heart failure(HF). LBBB associated nonischemic-cardiomyopathy (LB-NICM) with minimal or no scar by cardiac-magnetic-resonance(CMR) imaging may be associated with excellent prognosis following CRT. Left-bundle-branch-pacing(LBBP) can achieve excellent resynchronization in LBBB patients.

OBJECTIVES

Aim of our study was to prospectively assess feasibility and efficacy of LBBP with or without a defibrillator in patients with LB-NICM and LVEF ≤35%, risk stratified by CMR.

METHODS

Pts with LB-NICM, LVEF≤35% and HF were prospectively enrolled from 2019 to 2022. If the scar burden<10% by CMR, LBBP only (Group-I) and if ≥10%, LBBP+ICD(Group-II) was performed. Primary endpoints-1.Echocardiographic-response(ER)- ΔLVEF ≥15% at 6 months; 2.Composite of time to death, HFH or sustained VT/VF. Secondary endpoints-1.Echocardiographic-hyper-response(EHR-LVEF≥50%orΔLVEF ≥20%) at 6 and 12 months; 2.Indication for ICD-upgradation(persistent LVEF<35% at 12 months or sustained VT/VF) RESULTS: 120 patients were enrolled. CMR showed <10% scar-burden in 109 patients(90.8%). 4 patients opted for LBBP+ICD and withdrew. LBBP optimized-dual-chamber-pacemaker(LOT-DDD-P) was done in 101 patients and LOT-CRT-P in 4 patients(Group-I,n=105). Scar-burden ≥10% in 11 pts who underwent LBBP+ICD(Group-II). During mean-follow-up 21±12 months, primary endpoint of ER observed in 80%(68/85 pts) in Group-I vs 27%(3/11 pts) in Group-II(p-0.0001). Primary composite-endpoint of death,HFH or VT/VF occurred in 3.8% in group-I vs 33.3% in Group-II(p<0.0001). Secondary endpoint of EHR(LVEF≥50%) observed in 39.5%vs0%, 61.2%vs9.1% and 80%vs33.3% at 3, 6 and 12 months in group-I and group-II respectively.

CONCLUSION

CMR guided CRT using LOT-DDD-P appears to be a safe and feasible approach in LB-NICM and has the potential to reduce healthcare cost.

Left bundle branch area pacing in mildly reduced heart failure: A systematic literature review and meta-analysis

Cardiac resynchronization therapy (CRT) strategy for heart failure with mildly reduced ejection fraction (HFmrEF) is controversial. Left bundle branch area pacing (LBBAP) is an emerging pacing modality and an alternative option to CRT. This analysis aimed to perform a systematic review of the literature and meta-analysis on the impact of the LBBAP strategy in HFmrEF, with left ventricular ejection fraction (LVEF) between 35% and 50%. PubMed, Embase, and Cochrane Library were searched for full-text articles on LBBAP from inception to July 17, 2022. The outcomes of interest were QRS duration and LVEF at baseline and follow-up in mid-range heart failure. Data were extracted and summarized. A random-effect model incorporating the potential heterogeneity was used to synthesize the results. Out of 1065 articles, 8 met the inclusion criteria for 211 mid-range heart failure patients with an implant LBBAP across the 16 centers. The average implant success rate with lumenless pacing lead use was 91.3%, and 19 complications were reported among all 211 enrolled patients. During the average follow-up of 9.1 months, the average LVEF was 39.8% at baseline and 50.5% at follow-up (MD: 10.90%, 95% CI: 6.56-15.23, p < .01). Average QRS duration was 152.6 ms at baseline and 119.3 ms at follow-up (MD: -34.51 ms, 95% CI: -60.00 to -9.02, p < .01). LBBAP could significantly reduce QRS duration and improve systolic function in a patient with LVEF between 35% and 50%. Application of LBBAP as a CRT strategy for HFmrEF may be a viable option.

Changes of repolarization parameters after left bundle branch area pacing and the association with echocardiographic response in heart failure patients

Background: Left bundle branch area pacing (LBBAP) has become a safe and effective option for heart failure (HF) patients indicated for cardiac resynchronization therapy (CRT) and/or ventricular pacing, yet the response rate was only 70%. Repolarization parameters were demonstrated to be associated with cardiac mechanics and systolic function. This study aimed to investigate the effects of LBBAP on repolarization parameters and the potential association between those parameters and echocardiographic response.

Methods and results: A total of 59 HF patients undergoing successful LBBAP were consecutively included. QTc, Tpeak-Tend (TpTe), and TpTe/QTc were measured before and after the implantation. The results turned out that the dispersion of ventricular repolarization (DVR) improved after LBBAP among the total population. Although trends of repolarization parameters varied according to different QRS configurations at baseline, the post-implant parameters showed no significant difference between groups. The association between repolarization parameters and LBBAP response was then evaluated among patients with wide QRS. Multivariate analysis demonstrated that post-implant TpTe was the independent predictor of LBBAP response (p < 0.05). Receiver operating characteristic analysis indicated an area under the curve of 0.77 (95% CI, 0.60–0.93) with a cutoff value of 81.2 ms (p < 0.01). Patients with post-implant TpTe<81.2 ms had a significantly higher rate of echocardiographic response (93.3 vs. 44.4%, p < 0.01). Further subgroup analysis indicated that the predictive value of post-implant TpTe for LBBAP response was more significant in non-left bundle branch block (LBBB) patients than in LBBB patients.

Conclusion: LBBAP improved DVR significantly in HF patients. Post-implant TpTe was associated with the echocardiographic response after LBBAP among patients with wide QRS, especially for non-LBBB patients.

Effects of guideline-directed medical therapy in patients with left bundle branch block-induced cardiomyopathy

INTRODUCTION AND OBJECTIVES

Left bundle branch block (LBBB)-induced cardiomyopathy occurs in patients with long-standing LBBB. These patients characteristically exhibit hyperresponsiveness to cardiac resynchronization therapies (CRT). However, there is scarce information on their response to medical treatment. The aim of this study was to assess the change in left ventricular ejection fraction (LVEF) after a 3-month period following titration of guideline-directed medical therapy for heart failure.

METHODS

This retrospective analysis included all patients assessed in the heart failure unit of a Spanish University Hospital between 2020 and 2021, who presented with de novo ventricular dysfunction (LVEF <40%) and had a history of long-standing LBBB with no other possible causes of cardiomyopathy.

RESULTS

A total of 1497 patients were analyzed, of which 21 were finally eligible. Mean time from first diagnosis of LBBB to first consultation was 4.05± 4.1 years. Mean LVEF from first consultation to end of titration improved from 29.5±5.7% to 32.7±8.6% (P = .172), but none had recovered ventricular function at the end of follow-up. New York Heart Association functional class improved from 1.91±0.46 to 1.81±0.53 (P=.542). After CRT device implantation in 8 patients, LVEF improved by 18.1±6.4% (P=.003).

CONCLUSIONS

Guideline-directed medical therapy seems to be ineffective in improving LVEF and functional class in patients with de novo heart failure and LBBB-induced cardiomyopathy. Based on a positive response to CRT on LVEF improvement, early CRT implantation could be a reasonable strategy for these patients.

A Mild Dyssynchronous Contraction Pattern Detected by SPECT Myocardial Perfusion Imaging Predicts Super-Response to Cardiac Resynchronization Therapy

Background

Using single photon emission computed tomography myocardial perfusion imaging (SPECT MPI) with phase analysis (PA), we aimed to identify the predictive value of a new contraction pattern in cardiac resynchronization therapy (CRT) response.

Methods

Left ventricular mechanical dyssynchrony (LVMD) was evaluated using SPECT MPI with PA in non-ischemic dilated cardiomyopathy (DCM) patients with left bundle branch block (LBBB) indicated for CRT. CRT super-response was defined as LV ejection fraction (EF) ≥50% or an absolute increase of LVEF >15%. The LV contraction was categorized as the mild dyssynchronous pattern when the phase standard deviation (PSD) ≤ 40.3° and phase histogram bandwidth (PBW) ≤ 111.9°, otherwise it was defined as severe dyssynchronous pattern which was further characterized as U-shaped, heterogeneous or homogenous pattern.

Results

The final cohort comprised 74 patients, including 32 (43.2%) in mild dyssynchronous group, 17 (23%) in U-shaped group, 19 (25.7%) in heterogeneous group, and 6 (8.1%) in homogenous group. The mild dyssynchronous group had lower PSD and PBW than U-shaped, heterogeneous, and homogenous groups (P < 0.0001). Compared to patients with the heterogeneous pattern, the odds ratios (ORs) with 95% confidence intervals (CIs) for CRT super-response were 10.182(2.43–42.663), 12.8(2.545–64.372), and 2.667(0.327–21.773) for patients with mild dyssynchronous, U-shaped, and homogenous pattern, respectively. After multivariable adjustment, mild dyssynchronous group remained associated with increased CRT super-response (adjusted OR 5.709, 95% CI 1.152–28.293). Kaplan-Meier curves showed that mild dyssynchronous group demonstrated a better long-term prognosis.

Conclusions

The mild dyssynchronous pattern in patients with DCM is associated with an increased CRT super-response and better long-term prognosis.

Short QRS Duration After His-Purkinje Conduction System Pacing Predicts Left Ventricular Complete Reverse Remodeling in Patients With True Left Bundle Branch Block and Heart Failure

Objective

This study aimed to explore the outcomes of His-Purkinje conduction system pacing (HPCSP) and to screen the predictors of left ventricular (LV) complete reverse remodeling in patients with true left bundle branch block (LBBB) and heart failure with reduced ejection fraction (HFrEF).

Methods

Patients who underwent HPCSP for true LBBB and HFrEF from April 2018 to August 2020 were consecutively enrolled. All participants were followed up for at least 1 year. Thrombosis, infection, lead dislodgement, perforation, and other complications were observed after HPCSP. Clinical data, including echocardiographic parameters, electrocardiogram measurements, and cardiac function, were assessed before and after the procedure.

Results

A total of 46 patients were enrolled. HPCSP was successfully deployed in 42 cases (91.30%), which included 37 cases with His bundle pacing (HBP) and 5 cases with left bundle branch pacing (LBBP). The QRS duration decreased significantly (169.88 ± 19.17 ms vs. 113.67 ± 20.68 ms, P < 0.001). Left ventricular end-systolic volume (LVESV) (167.67 ± 73.20 ml vs. 85.97 ± 62.24 ml, P < 0.001), left ventricular end-diastolic diameter (LVEDD) (63.57 ± 8.19 mm vs. 55.46 ± 9.63 mm, P = 0.003) and left ventricular ejection fraction (LVEF) (26.52 ± 5.60% vs. 41.86 ± 11.56%, P < 0.001) improved dramatically. Complete reverse remodeling of the LV with normalized LVEF and LVEDD was found in nearly half of the patients (45.24%). A short QRS duration after HPCSP was a strong predictor of normalized LVEF and LVEDD (P < 0.001). The thresholds increased markedly in two patients approximately 6 months after HBP. No patients died during the total follow-up period of 20.07 ± 6.45 months.

Conclusion

Complete reverse remodeling of the LV could be found in nearly half of the patients with HFrEF and true LBBB after HPCSP, and the short QRS duration after HPCSP was a strong predictor.

Complete electrical reverse remodeling of native conduction after resynchronization therapies

BACKGROUND

Electrical reverse remodeling of native conduction is associated with better clinical outcome following cardiac resynchronization therapy (CRT). We aimed to describe characteristics, time course and long-term outcome of patients with complete electrical reverse remodeling (CERR) after resynchronization therapies.

METHODS

CRT candidates were treated with bi-ventricular, His bundle or left bundle branch pacing. CERR was defined if native QRS duration post-implantation was narrowed to ≤120 ms.

RESULTS

A total of 322 patients met the inclusion criteria. Among them, 66 were super-responders and 12 exhibited CERR. All 12 patients were diagnosed of non-ischemic cardiomyopathy with left bundle branch block (LBBB) meeting the Strauss criteria. The mean native QRS duration when CERR was achieved was 110.8 ± 10.0 ms, significantly shorter than the baseline (175.0 ± 18.8 ms). The occurrence of CERR varied from several days post-implantation to 18-month follow-up. The persistence of CERR also showed great variations. Eleven patients (91.7%, 11/12) showed echocardiographic super-response. Patients with CERR showed similar baseline characteristics compared to those with echocardiographic super-response but without CERR. Two patients with CERR showed different responses after bi-ventricular pacing was turned off. One patient remained stable with narrow QRS complex and great response. The other patient had reappearance of LBBB and decreased cardiac function, but recovered by turning on the device again.

CONCLUSIONS

Patients with CERR exhibited great response to different resynchronization therapies. The time course of CERR and echocardiographic super-response varied greatly. The variability of native conduction system and accompanied changes of mechanical remodeling suggest the mechanisms of electrical-disorder related cardiomyopathy.