Left Bundle Branch Block Patients Research Articles

Abstract 4135080: Relation of focal and diffuse myocardial fibrosis to left bundle branch block in patients with dilated cardiomyopathy and structurally normal heart

The role of fibrosis in etiology of left bundle branch block (LBBB) in still not defined. The aim of this study was to assess the relation of focal and diffuse LV fibrosis to LBBB in patients with dilated cardiomyopathy (DCM) and in patients with structurally normal heart. Materials and methods: 60 DCM with LBBB (DCM-LBBB group, 46.7% male, mean age 57[50;63] years), 50 non-LBBB DCM (78% male, mean age 43[32.3;54] years), 15 patients (53.3% male, mean age 39[28;50] years) with LBBB and no signs of structural heart disease and 10 healthy volunteers (HV) were included in the study. Endomyocardial biopsy (EMB) was performed in 15(24,6%) LBBB-DCM and 16(32%) non-LBBB DCM patients and allowed the quantification of collagen volume fraction (CVF, Fig.1A-D). All patients and HV underwent cardiovascular magnetic resonance (CMR) with late gadolinium enhancement (LGE) analysis. Obtained LGE LV images were post-proceed for core scar (CS) and gray zone (GZ) calculation and 3D reconstruction. Diffuse LV interstitial fibrosis was estimated on all LGE-CMR images with the novel introduced marker - diffuse intensity ratio (DIR). Results: DIR was validated on EMB samples: the percentage of CVF (8.2[4.6;10.8]%) correlated with the DIR value (0.71 ± 0.13) in the same segment (r=0.66, p<0.001, Fig.1E-F). The value of CVF (Fig1A-D) and LGE presence in the septum in both DCM groups (Fig2) was comparable (8.2[4.6; 10.3] versus 7.6[6.1;15.3]%, p=0.82 and 19 (31.7%) versus 17 (34%) patients in non-LBBB DCM group respectively, p=0.8) Moreover, the presence of LGE and midwall fibrosis in septum was not related to the QRS duration (p=0.93 and 0.59). In non-LBBB DCM patients the percentage of CS was significantly higher (4.0[1.55; 11.68]% versus 1.4[0.05;8.5]% in LBBB-DCM patients, p=0.047), whereas percentage of GZ and total fibrosis in both DCM groups was comparable (Fig.3A,B). DIR value was higher in patients with idiopathic LBBB than in HV (0.54±0.09 versus 0.34±0.1, p<0.001) while the percentage of GZ and CS was extremely low and did not differ from its amount in HV (Fig.3C,D). Conclusion: Neither focal (including midwall striae) nor interstitial fibrosis is associated with LBBB in patients with DCM. Diffuse inflammation in LBBB-DCM patients may contribute to the progression of systolic dysfunction but is not the reason for LBBB. The increased value of interstitial fibrosis in patients with LBBB may reflect latent diffuse process in myocardium inexorably leading to DCM development.

Abstract 4135061: Myocardial work in different patients with electrical dysynchrony due to left bundle branch block

Left bundle branch block (LBBB) in patients with dilated cardiomyopathy (DCM) is defined by huge wasted work and decreased myocardial constructive work. The aim of this study is to assess the myocardial work in patients in LBBB and other clinical situations. Materials and methods: The echocardiographic study was performed in 25 patients with LBBB and DCM (LBBB-DCM); 20 patients with DCM and narrow QRS complex (nonLBBB-DCM group); 15 patients with LBBB developed after transcatheter aortic valve implantation (TAVI group); 12 patients with idiopathic LBBB, normal systolic LV function and excluded cardiovascular pathology (LBBB group); 27 patients with right ventricular pacing due to atrioventricular block of high grade (RVP group) and 20 healthy volunteers (HV group). In all of them global longitudinal strain (GLS) and myocardial work parameters including global constructive work (GCW), global wasted work (GWW), global work index (GWI) and global work efficiency (GWE) were assessed. In all patients the segments with maximum and minimum GWI value were determined. Results: GLS, GWI and GCW values were comparable in LBBB and RVP groups, whereas in TAVI and in both DCM groups they was significantly lower than in HV (p = 0.049, 0.006, 0.025; p < 0,001 respectively, (Fig.1A,B,C)). Patients from LBBB, TAVI, RVP and LBBB-DCM groups were characterized by increased amount of GWW (261 [203.5; 291.5], 273 [184.8; 385,3] and 237 [149.5; 445.3] vs 108 [74.3; 137.3] mmHg%, p = 0.033, 0.006, < 0.001, < 0.001 respectively). GWW value in LBBB-DCM group was the highest (346.5 [255.5; 437.8] mmHg% (Fig.1D). There was moderate strength of relation between GWW and QRS duration (ρ=0.456, p<0.001). A huge amount of wasted work affected the GWE value and led to its considerable reduction in LBBB, TAVI, RVP and LBBB-DCM groups compared to HV (p = 0.033, 0.007, 0.023, < 0,001, respectively, Fig.1E). The zone of maximum GWI localized in posterolateral wall, the zone of minimum GWI was in interventricular septum in most LBBB patients (Fig.1F). At the same time, these zones turned out to be very variable in RVP group. Conclusion: Although all patients with LBBB pattern of electrical activation are characterized by significant amount of wasted work, its contribution to global myocardial work manifested only in DCM patients. Wasted work doesn’t lead to reduced constructive work in patients with idiopathic LBBB and RVP and normal systolic function probably due to compensatory mechanisms.

Right bundle branch block in suspected acute coronary syndromes: Diagnostic challenges, treatment and prognosis

BackgroundThere is still conflicting evidence regarding the prognostic implications of right bundle branch block (RBBB) in the general population but also in patients with heart diseases like acute coronary syndromes (ACS). In accordance with current guidelines, RBBB in ACS patients is considered as STEMI equivalent. However, recent studies indicate that further differentiation is necessary in this group, as we will outline below. Methods and resultsA literature search was conducted in PubMed and Google Scholar.In previous studies, RBBB in the general population were mostly considered benign changes of the electrical conduction system. However, recent studies indicate that both complete and incomplete RBBB are associated with increased cardiovascular morbidity and mortality. In addition, among unselected patients with suspected ACS presenting to the emergency department, the prevalence of RBBB was 3 % and it was associated with elevated mortality. The subsequent angiographic identification of a culprit coronary artery stenosis leading to stent implantation was similar at approximately 2 % regardless of the initial ECG presentation with narrow QRS complexes, left bundle branch block (LBBB), or RBBB.Finally, in a group of high-risk patients for ST-elevation myocardial infarction (STEMI), the prevalence of RBBB was 12 %. While RBBB was associated with poor outcome compared to non-BBB and LBBB patients, diagnostic accuracy of STEMI criteria was not affected by the presence of RBBB. However, RBBB patients without distinct STEMI signs in ECG often showed acute STEMI on angiography indicating a potential benefit from immediate transfer to the cardiac catheterization laboratory. ConclusionIn the general population, patients with RBBB and risk factors may need further evaluation. Regarding ACS patients, recent studies support current guidelines that recommend acute invasive evaluation for high-risk ACS patients with RBBB, regardless of ST-T deviations. However, in an unselected group of ACS patients, differential diagnoses should also be investigated through additional diagnostic procedures.

Effect of physical activity level on the association of LBBB, heart failure, and mortality

Abstract Background The beneficial effect of physical activity (PA) on adverse cardiovascular outcomes in patients with heart failure (HF) and left bundle branch block (LBBB) is well established. Yet, the impact of PA on individuals with LBBB without evident HF remains unexplored. Our objective is to investigate how PA modifies the outcomes of new-onset LBBB patients concerning HF-related hospitalizations and mortality. Methods Among the UK Biobank participants without a diagnosis of HF, we identified individuals with new-onset LBBB and available PA quantification. Patients were dichotomized into normal QRS and LBBB groups, following by stratification according to summed minutes of PA per week. The primary outcome was all-cause mortality, and HF-related hospitalizations. Cox proportional hazard model and Kaplan-Meier survival analysis were applied. Results The final cohort comprised 367,934 individuals, with a mean age of 56.6±8.2 years and 47% male. Among them, 3,427 (0.9%) developed new-onset LBBB, characterized by advanced age, male predominance, and higher rates of comorbidities. Median summed PA minutes per week were 100 (IQR: 125-180), with no significant difference between normal QRS and LBBB patients. Over a median follow-up of 13.8 years (IQR: 13-14.5), 26,304 patients (7.15%) died. Kaplan-Meier analysis revealed higher mortality risk with reduced PA level and/or LBBB (log-rank p<0.001 for both). Multivariate Cox analysis adjusted for age, sex, and comorbidities showed LBBB patients had over 3.5-fold increased risk of death (HR 3.67, 95% CI 3.39-3.97, p<0.001) compared to normal QRS. The association of LBBB with mortality was modified by weekly PA minutes; those with <150 minutes had nearly 40% higher risk compared to those with ≥150 minutes (HR 3.78, 95% CI 3.43–4.15, p<0.001; HR 3.4, 95% CI 2.93–3.95, p<0.001; p for interaction=0.035). The protective effect of PA was 6% among normal QRS patients, compared to 22% among individuals with LBBB (HR 0.94, 95% CI 0.91 – 0.96, p<0.001 vs. HR 0.78, 95% CI 0.66 – 0.93, p=0.004). Similar findings were observed for HF hospitalizations. Conclusions Although the correlation between LBBB and adverse cardiovascular outcomes remained consistent across both levels of physical activity (PA), it was more pronounced among patients with low PA levels. When assessing the risk in patients with newly diagnosed LBBB, particular attention should be directed towards their PA status.

CMR characterisation of patients with heart failure and left bundle branch block

Abstract Introduction Cardiac magnetic resonance (CMR) is recommended internationally for tissue characterisation, volumetric assessment and assessment of prior myocardial infarction (1). Patients with left bundle branch block (LBBB) form a significant sub-group of individuals, however, there is limited data available to accurate determine whether LBBB is associated with any CMR-definable phenotypes. Aim We aimed to identify the distinctive cardiac magnetic resonance (CMR) features of patients with left bundle branch block (LBBB) and heart failure with reduced ejection fraction (HFrEF) of presumed non-ischaemic aetiology. Methods Participants from the MATCH (MyocArdial Tissue CHaracteristics in patients with heart failure according to glycaemic status) registry were prospectively enrolled. Exclusion criteria included: LVEF >40% at initial evaluation, established diagnosis of coronary artery disease, known presence of structural heart disease, suspected myocarditis, congenital heart disease and significantly impaired renal function. Following identification of HF, guideline-directed medical therapy was initiated based on the decision of the treating physician. LV recovery was defined as achieving ≥10% absolute improvement to a level of 40% or greater of LVEF from baseline evaluation upon the date of CMR quantification. Electrocardiograms were analysed to establish the presence or absence of LBBB. Results A total of 391 patients were recruited including 115 (29.4%) presenting with LBBB. Compared to controls, LBBB patients exhibited larger left ventricles and smaller right ventricles, but no differences were observed with respect to LVEF (35.8±12 vs. 38± 12 %, p=0.105) or right ventricular ejection fraction (RVEF). The prevalence of ischaemic scar (18.3% vs 21%, p=0.54), non-ischaemic fibrosis (25.2% vs 32.6%, p=0.15) and inducible ischaemia (6.1% vs. 7.6%, p=0.6) was comparable in patients with LBBB and those without. The overall rate of LV recovery was not significantly different between LBBB and non-LBBB patients (27.8% vs. 33%, p=0.32) from their baseline evaluation to the time of CMR assessment (70 [42 - 128] days). In the multivariate logistic regression, reduced LVEF remained an independent predictor of LV non-recovery in patients with LBBB, even after adjusting for gender and QRS duration (OR 0.93, 95%CI 0.87 – 0.99, p=0.03). In contrast, this association was not observed among patients without LBBB, whereas ischaemic scar was the primary predictor of LV non-recovery (OR 4.31, 95%CI 1.85 – 10.04, p=0.0007). Conclusion In this study patients presenting with a combination of HFrEF and LBBB had a larger LV cavity and smaller RV cavity than those without LBBB. However, there were no differences in the prevalence of ischaemic scar, non-ischaemic scar of inducible ischaemia according to the presence of absence of LBBB. Rates of LV recovery were similar between LBBB and non-LBBB patients.Clinical CMR ParametersSegmental Distributions

Mitral regurgitation improvement following left bundle branch pacing versus right ventricular septum pacing: a dedication to postoperative amelioration of mitral regurgitation

Abstract Background Mitral regurgitation (MR) is correlated with left ventricular (LV) remodeling and LV function in patients. Left bundle branch pacing (LBBP) exhibits a significant decline in MR in left bundle branch block (LBBB) and cardiomyopathy patients. This research aims to evaluate the influence of LBBP on MR in comparison to right ventricular septal pacing (RVSP) in patients with atrioventricular block (AVB) or sick sinus syndrome (SSS). Methods Sixty consecutive patients with SSS or AVB were enrolled if they underwent pacemaker implantation via LBBP or RVSP. Patients with a history of mitral valve surgery were excluded. Echocardiogram parameters were assessed to measure MR and LV remodeling as well as LV function at baseline and follow-up. Results Thirty-six patients (60 %; mean age: 70.39 ± 14.80 years; 61.1 % male) underwent successful LBBP, and 24 patients (40 %; mean age: 71.58 ± 10.91 years; 66.7 % male) underwent RVSP. The average follow-up duration was relatively comparable between the two groups. In comparison to RVSP, LBBP demonstrated significant changes in MR area, and severity at baseline and follow-up (P<0.05). LBBP independently predicted MR amelioration in patients who underwent pacemaker implantation (HR=0.289, CI=0.087–0.9961; P=0.043). At follow-up, the LBBP subgroup with moderate/severe MR exhibited significantly shorter lead-TVA-dist, higher left atrium (LA) diameters, and mitral E/A ratio (P<0.05) compared to the none/mild MR subgroup. In LBBP with MR amelioration, LV remodeling (ΔLVEDD) was significantly enhanced compared to baseline (P=0.016). Additionally, a non-significant trend toward better improvement in LV function (ΔLVEF and ΔE/A) was observed in patients with MR amelioration. Conclusion LBBP, considered an optimal pacing technique for SSS or AVB patients, may substantially reduce MR and subsequently enhance LV remodeling and function compared to RVSP. This open, observational pilot study warrants confirmation through further investigations.Comparison between LBBP and RVSPKaplan-Meier curves for MR amelioration

Predictive value of apical rocking and septal flash for subclinical left ventricular systolic dysfunction in complete left bundle branch block patients with normal left ventricular ejection fraction

BackgroundThis study aimed to evaluate the effects of apical rocking(ApRock) and septal flash(SF) on left ventricular function in complete left bundle branch block(CLBBB) patients with normal left ventricular ejection fraction(LVEF), with the goal of improving risk stratification and clinical decision-making for these patients. MethodsSeventy-five CLBBB patients with normal LVEF, and 30 age- and sex-matched controls were enrolled in the study. Three independent physicians visually assessed the presence of ApRock and SF and left ventricular global longitudinal strain(LVGLS) and the standard deviation of time-to-peak strain in 18 segments(Ts-SD) were evaluated using two-dimensional speckle-tracking echocardiography. ResultsCLBBB patients with normal LVEF had significantly decreased LV function and synchrony as evidenced by LVGLS and Ts-SD, and CLBBB patients with either ApRock or SF had lower LVGLS than those without ApRock or SF. LVGLS were further decreased and Ts-SD was further increased in CLBBB patients with both ApRock and SF (P < 0.001). Logistic regression analysis revealed that both ApRock (OR, 4.13; P = 0.04) and SF (OR, 4.12; P = 0.03) were independently associated with LVGLS>-20 %. Combination of ApRock and SF showed the highest area under the curve for identifying LVGLS>-20 %. Furthermore, combination of ApRock and SF improved reclassification compared to ApRock alone. ConclusionCLBBB patients with normal LVEF showed impaired left ventricular systolic function. The presence of both ApRock and SF was a stronger indicator of subclinical left ventricular impairment compared to either one alone, suggesting that increased attention should be paid to CLBBB patients with normal LVEF, particularly those with both ApRock and SF.

Electrocardiographic Criteria for the Diagnosis of Acute Myocardial Infarction in Patients with Left Bundle Branch Block

During normal conduction system, the first segment depolarized is interventricular septum, normal ventricular depolarization begins with the septal fascicle of the left bundle branch followed by a simultaneous depolarization of the remaining ventricular walls from endocardium to pericardium via the right and left bundle branches. In left bundle branch block (LBBB) condition, the left ventricular activation is delayed, and the initial septal activation is from right to left, secondary ST segment and T wave abnormalities occur, and septal Q waves indicative of an MI are absent. About 0.5 percent of patients with acute myocardial infarction had left bundle-branch block Patients with left bundle branch block (LBBB) and suspected of acute myocardial infarction (MI) is challenge to the clinician. A diagnosis of MI with electrocardiogram (ECG) is especially difficult in the setting of LBBB because of the characteristic ECG changes caused by altered septal and left free wall ventricular depolarization. Here we review the pathophysiology of LBBB in MI, highlight evolving paradigms for the diagnosis of suspected MI in patients with LBBB.

Evaluating Long-Term Outcomes in STEMI Patients with New Left Bundle Branch Block: The Impact of Modifiable Risk Factors.

Background/Objectives: Coronary artery disease, a leading global cause of death, highlights the essential need for early detection and management of modifiable cardiovascular risk factors to prevent further coronary events. Methods: This study, conducted at a major tertiary academic PCI-capable hospital in Romania from 1 January 2011 to 31 December 2013, prospectively analyzed 387 myocardial infarction with ST-segment elevation (STEMI) patients to assess the long-term management of modifiable risk factors. This study particularly focused on patients with new-onset left bundle branch block (LBBB) and compared them with a matched control group without LBBB. Results: During median follow-up periods of 9.6 years for LBBB patients and 9.2 years for those without LBBB, it was found that smoking, obesity, and dyslipidemia were prevalent in 73.80%, 71.42%, and 71.42% of the LBBB group, respectively, at baseline. Significant reductions in smoking were observed in both groups, with the LBBB group's smoking rates decreasing significantly to 61.90% (p = 0.034). Patients with LBBB more frequently achieved low-density lipoprotein cholesterol (LDLc) target levels during the follow-up period (from 71.42% to 59.52%; p = 0.026) compared to the control group (from 66.67% to 71.42%; p = 0.046). Prescription rates for dual antiplatelet therapy (DAPT), angiotensin-converting enzyme inhibitors (ACEi) or angiotensin II receptor blockers (ARBs), beta-blockers, and statins were initially high but then decreased by the follow-up. Statin use was reduced from 97.62% to 69.04% (p = 0.036) in the LBBB group and from 100% to 61.90% (p = 0.028) in the non-LBBB group. This study also highlighted moderate correlations between obesity (r = 0.627, p = 0.040) and subsequent coronary reperfusion in the LBBB group, while dyslipidemia and smoking showed very strong positive correlations across both groups (dyslipidemia: r = 0.903, p = 0.019 for LBBB; r = 0.503, p = 0.048 for non-LBBB; smoking: r = 0.888, p = 0.035 for LBBB; r = 0.517, p = 0.010 for non-LBBB). Conclusions: These findings underscore the crucial need for targeted management of modifiable risk factors, particularly focusing on dyslipidemia and smoking cessation, to improve subsequent coronary reperfusion outcomes post-STEMI, especially in patients with complicating factors like LBBB.

Assessment of three-dimensional (3-D) left ventricular ejection fraction and speckled tracking echocardiographic strain parameters in non-ischemic left bundle branch block (LBBB) patients and their association with cardiovascular events – A prospective observational study

ObjectiveTo investigate the association between three-dimensional (3-D) left ventricular ejection fraction (LVEF) and various speckle tracking echocardiographic (STE) strain parameters in non-ischemic left bundle branch block (LBBB) patients with major adverse cardiovascular events (MACE) during a one-year follow-up phase. MethodA total of 50 patients with non-ischemic LBBB were assessed using various parameters of 3-D echocardiography. They were compared with their same-age and sex control group and then followed up with repeat 3-D echocardiography for MACE for one year. ResultsComposite outcomes were seen in (n = 11 [22 %], including cardiovascular mortality (n = 2 [4.0 %]) and hospitalization for heart failure (n = 9 [18.0 %]). Mean values of the left ventricle (LV) global longitudinal (GLS), circumferential (GCS), and radial (GRS) strains were −14.4 ± 5.6, −14.3 ± 5.8, and 15.3 ± 5.9 respectively in the study cases. Initial GLS values were significantly impaired among those who had clinical events (−9.2 vs −15.9). Also, significant worsening of GLS (p value < 0.001) was seen in patients with composite outcomes on follow-up. Cut-off values in receiver operating characteristic analyses for composite outcomes were: GLS more than −13.5, GCS more than −12.5, and GRS less than 14.5. Intra-class correlations for both intra-observer and inter-observer variability were found to be good. ConclusionImpaired LV GLS and low 3-D LVEF are significantly associated with the occurrence of MACE in patients with non-ischemic LBBB. This strong association of LV GLS with outcomes can aid in risk stratification, prognostication, and clinical decision-making in non-ischemic LBBB.

A porcine large animal model of radiofrequency ablation-induced left bundle branch block

Abstract Funding Acknowledgements Type of funding sources: Private company. Main funding source(s): Medtronic Background and Objective ECG features of left bundle branch (LBB) block (LBBB) can be observed in up to 20–30 % of patients that suffer from heart failure with reduced ejection fraction. The resulting mechanical intraventricular asynchrony contributes to the worsening of left ventricular hemodynamics and has a relevant impact on the prognosis of the affected patients. The fact that we still cannot accurately predict which LBBB patients will benefit from cardiac resynchronization therapy (CRT) underscores that our understanding of the pathophysiology of LBBB remains incomplete. Here, a translational animal model of LBBB could be a major contributor to improving our knowledge of the molecular and translational pathomechanisms underlying LBBB. Methods A total of 15 male pigs underwent RF catheter ablation of the LBB, guided by fluoroscopy and intracardiac ECG signals. Before LBBB induction and after a follow-up period of one week or three weeks, a thorough clinical characterization was performed including 12-lead ECG, echocardiography, and electroanatomical mapping. To further test the feasibility of cardiac resynchronization in our model, 3 pigs were implanted with a CRT pacemaker on day seven after LBB ablation. Results Upon LBB ablation, 12-lead ECGs displayed typical characteristics of LBBB like a QRS broadening, a QRS slurring in left lateral leads, and a change of the QRS axis. The QRS width was prolonged from 64.2±4.2 ms to 93,4±7.4 ms and the R wave peak time in V6 was extended from 19.3±3.9 ms to 42.7±4.2 ms. Cardiac electromechanical asynchrony was further confirmed by echocardiography, where the appearance of a septal flash, the prolongation of the septal to posterior wall movement delay and extended left ventricular as well as interventricular electromechanical delays were documented. Electroanatomical mapping demonstrated a shift of the left ventricular breakthrough site. After LBBB-induction, left ventricular activation times, defined as the average of the maximum 10 % of activation times minus the average of the minimum 10 % of activation times were significantly prolonged from 36.3±7.1 ms to 60.8±10.2 ms while right ventricular activation times remained unchanged. Finally, RF-induced LBBB persisted over an observation period of three weeks. The pigs that underwent CRT showed a reduction in QRS duration from 99.1±8.2 ms on day seven after LBBB induction to 75.5±8.2 ms and echocardiography provided additional evidence of successful resynchronization. Conclusions In summary, our porcine large animal model accurately recapitulates the electrical and electromechanical phenotype, observed in LBBB patients. This closed-chest model of LBBB therefore provides an experimental platform to study both, molecular and translational characteristics of cardiac electromechanical asynchrony in a reproducible and clinically relevant setting.

Precordial activation sequences from low frequency analysis in left bundle branch block patients: left bundle branch area pacing vs right ventricular pacing

Abstract Introduction Left bundle branch area pacing (LBBAP) provides a more synchronous and physiological ventricular activation than conventional right ventricular pacing (RVP) in LBBB patients. QRS duration (QRSd) is the standard measurement for assessing depolarization synchrony, but it only provides information about the activation time and not about the activation sequence. Purpose Our aim is to assess the activation sequence by precordial activation delay (pAD) using a low-frequency (LF) ECG method comparing baseline and paced ECG in LBBAP and RVP patients. Methods Twelve-lead ECGs recordings were acquired from 29 patients with LBBB (16 LBBAP and 13 RVP) after 24 hours of sequential LBBAP or RVP. LF-ECG was employed for QRS-complex analysis. The activation time for each lead was computed and an activation sequence constructed by linking them. pAD was calculated as the time between the first and the last lead activation. pAD provides information about both, the delay in ventricular depolarization as indicated by its magnitude, and the depolarization direction (as it can take a positive or negative value indicating a left or right ventricle delay, respectively). Results At baseline, both groups (LBBAP and RVP) showed the latest activation at V5-V6, supported by positive median pAD values with no statistically significant differences between both groups (50 (21, 65) vs. 54 (17, 67) ms, p=0.93). LBBAP reduced V6 delay and pAD values compared to the baseline QRS (basal: 50 (21, 65) vs. paced: 2 (-18, 25) ms, p&amp;lt;0.001) while RVP did not exhibit any difference (basal: 54 (17, 67) vs. paced: 36 (19, 53) ms, p=0.33). LBBAP provided lower pAD values when compared to RVP (2 (-18, 25) vs. 36 (19, 53) ms, p&amp;lt;0.01). Conclusions pAD measured using a LF-ECG analysis is a feasible method to evaluate depolarization synchrony and provides complementary information to QRSd. In contrast to RVP, LBBAP generates a physiological ventricular activation sequence in patients with LBBB.Baseline patients characteristicsVentricular activation sequences and pAD

Impact of left bundle branch block morphology in predicting response to left bundle branch area pacing for cardiac resynchronization therapy

Abstract Background Left bundle branch area pacing (LBBAP) is a novel pacing technique with an emerging role in resynchronization therapy [1-4]. QRS morphology has shown to significantly influence cardiac resynchronization therapy (CRT) response [5-6]. Purpose The aim of this study was to assess whether different left bundle branch block (LBBB) definitions are associated with response to LBBAP resynchronization therapy. Methods 40 consecutive CRT candidates with previously unsuccessful biventricular (BiV) pacing or in which effective CRT could not be achieved with BiV pacing based on anatomical or functional criteria were selected for this study. Both ischemic and non-ischemic heart failure (HF) patients were included. Patients were divided into two groups according to LBBB morphology. Group 1 included 20 patients (45% ischemic HF) with strict LBBB definition according to Strauss criteria [7], while 20 patients in Group 2 (55% ischemic HF) had conventional LBBB morphology. Response to CRT was defined for (1) reduction in QRS duration; (2) increase in left ventricular ejection fraction (LVEF) ≥ 5% and (3) decrease in left ventricular end systolic volume (LVESV) ≥ 15%. Results LBBAP was successfully achieved in all patients (mean age: 72.0 years; male: 29). The mean baseline QRS duration before implantation was 178.6±13.8 in the Group 1 and 170.8±29.4 in the Group 2, without a statistically significant difference. Over a mean follow-up of 5.6 months, LBBAP resulted in QRS narrowing in both groups, with a greater reduction in Group 1 (-40.6 ms) compared to Group 2 (-15.1 ms), (p 0.002). Pre-implantation ventricular systolic function did not show significant differences between the two groups, with a mean of 30.1±3.5% in the Strauss LBBB group and 31.0±6.0% in the conventional LBBB group. After implantation LVEF was 42.1±8.5 % in the true LBBB patients and 33.2±7.5 in the conventional LBBB group. Echocardiographic response was observed in 65% of patients with a statistically significant difference between Group 1 (90% of responders) and Group 2 (40% of responders), (p 0,001). HF etiology did not impact the response to LBBAP CRT. Conclusions Strict LBBB definition is associated to a greater electrocardiographic and echocardiographic response in patients receiving LBBAP CRT compared to conventional LBBB criteria.\

Quantification of left ventricular myocardial strain: Comparison between MRI tagging, MRI feature tracking, and ultrasound speckle tracking.

Ultrasound speckle tracking is frequently used to quantify myocardial strain, and magnetic resonance imaging (MRI) feature tracking is rapidly gaining interest. Our aim is to validate cardiac MRI feature tracking by comparing it with the gold standard method (i.e., MRI tagging) in healthy subjects and patients. Furthermore, we aim to perform an indirect validation by comparing ultrasound speckle tracking with MRI feature tracking. Forty-two subjects (17 formerly preeclamptic women, three healthy women, and 22 left bundle branch block patients of both sexes) received 3-T cardiac MRI and echocardiography. Cine and tagged MRI, and B-mode ultrasound images, were acquired. Intrapatient global and segmental left ventricular circumferential (MRI tagging vs. MRI feature tracking) and longitudinal (MRI feature tracking vs. ultrasound speckle tracking) peak strain and time to peak strain were compared between the three techniques. Intraclass correlation coefficient (ICC) (< 0.50 = poor, 0.50-0.75 = moderate, > 0.75-0.90 = good, > 0.90 = excellent) and Bland-Altman analysis were used to assess correlation and bias; pless than 0.05 indicates a significant ICC or bias. Global peak strain parameters showed moderate-to-good correlations between methods (ICC = 0.71-0.83, p< 0.01) with no significant biases. Global time to peak strain parameters showed moderate-to-good correlations (ICC = 0.56-0.82, p< 0.01) with no significant biases. Segmental peak strains showed significant biases in all parameters and moderate-to-good correlation (ICC = 0.62-0.77, p< 0.01), except for lateral longitudinal peak strain (ICC = 0.23, p= 0.22). Segmental time to peak strain parameters showed moderate-to-good correlation (ICC = 0.58-0.74, p< 0.01) with no significant biases. MRI feature tracking is a valid method to examine myocardial strain, but there is bias in absolute segmental strain values between imaging techniques. MRI feature tracking shows adequate comparability with ultrasound speckle tracking.

Outcomes with T-wave discordance of left bundle branch block and preserved or mildly reduced ejection fraction.

Left bundle branch block (LBBB) is associated with an increased risk of adverse outcomes for patients with heart failure. The prognosis of LBBB in patients with a preserved ejection fraction (EF) remains controversial. This study investigated the predictive value of T-wave discordance for the prognosis of patients with LBBB and preserved or mildly reduced EF. We enrolled 707 patients with complete LBBB and left ventricular (LV) EF≥40% observed using electrocardiograms (ECGs) and echocardiograms between January 2010 and December 2018. Their serial ECGs were reviewed during the follow-up period. The T-wave pattern was classified as discordant LBBB (dLBBB) or concordant LBBB (cLBBB) according to the 12-lead ECG T-wave morphology. The primary outcome was the composite of cardiovascular death or hospitalization for heart failure during a median follow-up period of 3.1years. A multivariable Cox regression analysis was used to evaluate the independent predictors of the primary outcome. Patients with dLBBB had more comorbidities, a higher heart rate, a longer QRS and QTc duration, a larger LV end-systolic volume and left atrial dimension, a lower LVEF, and a higher mitral E/A ratio and E/e', compared with those with cLBBB. Older age [hazard ratio (HR)=1.023, 95% confidence interval (CI)=1.001-1.046, P=0.023], history of heart failure (HR=2.440, 95% CI=1.524-3.905, P=0.001), chronic kidney disease (HR=1.917, 95% CI=1.182-3.110, P=0.008), larger LV end-systolic volume (HR=1.046, 95% CI=1.017-1.075, P=0.002), lower LVEF (HR=0.916, 95% CI=0.885-0.948, P=0.001), and presence of dLBBB (HR=1.63, 95% CI=1.011-2.628, P=0.032) were independent predictors of the primary outcome in patients with LBBB and LVEF≥40%. The discordant or concordant T-wave morphology of LBBB could transform from one subtype to the other in up to 23% of the study population during the follow-up period, and individuals with persistent or transformed dLBBB faced an increased risk of cardiovascular death or non-fatal heart failure hospitalization. In patients with LBBB and EF≥40%, dLBBB serves as an independent predictor of a higher risk of cardiovascular death or non-fatal heart failure hospitalization.

The influence of left bundle branch block on myocardial T1 mapping

Tissue characterisation using T1 mapping has become an established magnetic resonance imaging (MRI) technique to detect myocardial diseases. This retrospective study aimed to determine the influence of left bundle branch block (LBBB) on T1 mapping at 1.5 T. Datasets of 36 patients with LBBB and 27 healthy controls with T1 mapping (Modified Look-Locker inversion-recovery (MOLLI), 5(3)3 sampling) were included. T1 relaxation times were determined on mid-cavity short-axis images. R2 maps were generated as a pixel-wise indicator for the goodness of the fit of T1 maps. R2 values were significantly lower in patients with LBBB than in healthy controls (whole myocardium/septum, 0.997, IQR, 0.00 vs. 0.998, IQR, 0.00; p = 0.008/0.998, IQR, 0.00 vs. 0.999, IQR, 0.00; p = 0.027). Manual correction of semi-automated evaluation tended to improve R2 values but not significantly. Strain analysis was performed and the systolic dyssynchrony index (SDIglobal) was calculated as a measure for left ventricular dyssynchrony. While MRI is generally prone to artefacts, lower goodness of the fit in LBBB may be mainly attributable to asynchronous contraction. Therefore, careful checking of the source data and, if necessary, manual post-processing is important. New techniques might improve the goodness of the fit of T1 mapping by reducing sampling in the motion prone diastole of LBBB patients.

Conduction system disease management in patients candidate and/or treated for the aortic valve disease: an Italian Survey promoted by Italian Association of Arrhythmology and Cardiac Pacing (AIAC)

Background Conduction system disorders represent a frequent complication in patients undergoing surgical (surgical aortic valve replacement, SAVR) or percutaneous (transcatheter aortic valve implantation, TAVI) aortic valve replacement. The purpose of this survey was to evaluate experienced operators approach in this clinical condition. Methods This survey was independently conducted by the Italian Association of Arrhythmology and Cardiac Pacing (AIAC) and it consisted of 24 questions regarding the respondents’ profile, the characteristics of participating centres, and conduction disease management in different scenarios. Results Fifty-five physicians from 55 Italian arrhythmia centres took part in the survey. Prophylactic pacemaker implantation is rare. In case of persistent complete atrioventricular block (AVB), 49% and 73% respondents wait less than one week before implanting a definitive pacemaker after SAVR and TAVI, respectively. In case of second degree AVB, the respondents wait some days more for definitive implantation. Respondents consider bundle branch blocks, in particular pre-existing left bundle branch block (LBBB), the worst prognostic factors for pacemaker implantation after TAVI. The implanted valve type is considered a relevant element to evaluate. In patients with new-onset LBBB and severe/moderate left ventricular systolic dysfunction, respondents would implant a biventricular pacemaker in 100/55% of cases, respectively. Conclusions Waiting time before a definitive pacemaker implantation after aortic valve replacement has reduced compared to the past, and it is anticipated in TAVI vs. SAVR. Bundle branch blocks are considered the worse prognostic factor for pacemaker implantation after TAVI. The type of pacemaker implanted in new-onset LBBB patients without severe left ventricular systolic dysfunction is heterogeneous.

Assessment of myocardial strain patterns in patients with left bundle branch block using cardiac magnetic resonance.

Recently, a classification with four types of septal longitudinal strain patterns was described using echocardiography, suggesting a pathophysiological continuum of left bundle branch block (LBBB)-induced left ventricle (LV) remodeling. The aim of this study was to assess the feasibility of classifying these strain patterns using cardiovascular magnetic resonance (CMR), and to evaluate their association with LV remodeling and myocardial scar. Single center registry included LBBB patients with septal flash (SF) referred to CMR to assess the cause of LV systolic dysfunction. Semi-automated feature-tracking cardiac resonance (FT-CMR) was used to quantify myocardial strain and detect the four strain patterns. A total of 115 patients were studied (age 66 ± 11years, 57% men, 28% with ischemic heart disease). In longitudinal strain analysis, 23 patients (20%) were classified in stage LBBB-1, 37 (32.1%) in LBBB-2, 25 (21.7%) in LBBB-3, and 30 (26%) in LBBB-4. Patients at higher stages had more prominent septal flash, higher LV volumes, lower LV ejection fraction, and lower absolute strain values (p < 0.05 for all). Late gadolinium enhancement (LGE) was found in 55% of the patients (n = 63). No differences were found between the strain patterns regarding the presence, distribution or location of LGE. Among patients with LBBB, there was a good association between strain patterns assessed by FT-CMR analysis and the degree of LV remodeling and LV dysfunction. This association seems to be independent from the presence and distribution of LGE.

CMR characterization of patients with heart failure and left bundle branch block

Abstract Aims We aimed to identify the distinctive cardiovascular magnetic resonance (CMR) features of patients with left bundle branch block (LBBB) and heart failure with reduced ejection fraction (HFrEF) of presumed non-ischaemic aetiology. The secondary aim was to determine whether these individuals exhibit characteristics that could potentially serve as predictors of left ventricular ejection fraction (LVEF) recovery as compared with patients without LBBB. Methods and results We prospectively recruited patients with HFrEF (LVEF ≤ 40%) on echocardiography who were referred for early CMR examination. Patients with an established diagnosis of coronary artery disease and known structural or congenital heart disease were excluded. LV recovery was defined as achieving ≥10% absolute improvement to ≥40% in LVEF between baseline evaluation to CMR. A total of 391 patients were recruited including 115 (29.4%) with LBBB. Compared with HF patients without LBBB, those with LBBB exhibited larger left ventricles and smaller right ventricles, but no differences were observed with respect to LVEF (35.8 ± 12 vs. 38 ± 12%, P = 0.105). The overall rate of LV recovery from baseline echocardiogram to CMR (70 [42–128] days) was not significantly different between LBBB and non-LBBB patients (27.8% vs. 31.5%, P = 0.47). Reduced LVEF remained an independent predictor of LV non-recovery only in patients with LBBB. Conclusion Patients presenting with HFrEF and LBBB had larger LV cavities and smaller RV cavities than those without LBBB but no difference in prevalence of scar or ischaemia. The rates of LV recovery were similar between both groups, which supports current guidelines to defer device therapy until 3–6 months of guideline-directed medical therapy, rather than early CMR and device implantation.

A porcine large animal model of radiofrequency ablation-induced left bundle branch block.

Electrocardiographic (ECG) features of left bundle branch (LBB) block (LBBB) can be observed in up to 20%-30% of patients suffering from heart failure with reduced ejection fraction. However, predicting which LBBB patients will benefit from cardiac resynchronization therapy (CRT) or conduction system pacing remains challenging. This study aimed to establish a translational model of LBBB to enhance our understanding of its pathophysiology and improve therapeutic approaches. Fourteen male pigs underwent radiofrequency catheter ablation of the proximal LBB under fluoroscopy and ECG guidance. Comprehensive clinical assessments (12-lead ECG, bloodsampling, echocardiography, electroanatomical mapping) were conducted before LBBB induction, after 7, and 21days. Three pigs received CRT pacemakers 7days after LBB ablation to assess resynchronization feasibility. Following proximal LBB ablation, ECGs displayed characteristic LBBB features, including QRS widening, slurring in left lateral leads, and QRS axis changes. QRS duration increased from 64.2 ± 4.2ms to 86.6 ± 12.1ms, and R wave peak time in V6 extended from 21.3 ± 3.6ms to 45.7 ± 12.6ms. Echocardiography confirmed cardiac electromechanical dyssynchrony, with septal flash appearance, prolonged septal-to-posterior-wall motion delay, and extended ventricular electromechanical delays. Electroanatomical mapping revealed a left ventricular breakthrough site shift and significantly prolonged left ventricular activation times. RF-induced LBBB persisted for 3weeks. CRT reduced QRS duration to 75.9 ± 8.6ms, demonstrating successful resynchronization. This porcine model accurately replicates the electrical and electromechanical characteristics of LBBB observed in patients. It provides a practical, cost-effective, and reproducible platform to investigate molecular and translational aspects of cardiac electromechanical dyssynchrony in a controlled and clinically relevant setting.