Typical Left Bundle Branch Block Research Articles

Evaluation of electrocardiographic criteria for predicting left ventricular hypertrophy and dilation in presence of left bundle branch block

BackgroundThe utility of standard published electrocardiographic (ECG) criteria for left ventricular hypertrophy (LVH) in patients with left bundle branch block (LBBB) is not established. We have previously shown that in ECGs demonstrating LBBB, QRS duration outperforms vectorcardiographic X, Y, Z lead and root-mean-squared (3D) amplitudes and voltage-time-integrals in diagnosing LVH and dilation. We sought to evaluate diagnostic yields of published LVH criteria versus QRS duration for ECG based diagnosis of LVH and dilation in presence of LBBB. MethodsWe included adult patients with typical LBBB having ECG and transthoracic echocardiogram performed within 3 months of each other in 2010–2020. We obtained area under receiver-operator characteristic curve (AUC) for QRS duration and each of the published ECG LVH criteria to predict increased LV mass indexed (↑LVMi, women >95 g/m2, men >115 g/m2) and LV end diastolic volume indexed (↑LVEDVi, women >61 mL/m2, men >74 mL/m2). ResultsAmong 413 adults (53 % women, age 73 ± 12 yr) with LBBB, the traditional LVH criteria performed poorly to detect ↑LVMi or ↑LVEDVi. Cornell voltage-duration product had the highest AUCs (↑LVMi 0.634, ↑LVEDVi 0.580). QRS duration had a higher AUC for diagnosing ↑LVMi (women 0.657, men 0.703) and ↑LVEDVi (women 0.668, men 0.699) compared to any other criteria. ConclusionsIn patients with LBBB, prolonged QRS duration (women ≥150 ms, men ≥160 ms) is a superior predictor of LVH and dilation than traditional ECG-based LVH criteria.

Sex differences outcomes in conduction system pacing for patients with typical left bundle branch block

BackgroundBiventricular pacing (BVP) appears to confer more pronounced advantages in women, yet the impact of conduction system pacing (CSP) remains insufficiently characterized. This investigation seeks to elucidate sex-specific disparities in clinical outcomes among patients with typical left bundle branch block (LBBB) undergoing CSP, with a particular focus on assessing contributory factors. MethodsConsecutive patients diagnosed with nonischemic cardiomyopathy, exhibiting left ventricular ejection fraction (LVEF) ≤ 40%, and manifesting typical LBBB as Strauss criteria, underwent CSP. Subsequent longitudinal monitoring assessed improvements in LVEF and the composite endpoint of mortality or heart failure hospitalization (HFH). ResultsAmong the included 176 patients, women (n = 84, mean age: 69.5 ± 8.8 years) displayed smaller heart size (LVEDd, 62.0 ± 8.3 mm vs. 64.8 ± 7.9 mm, P = 0.023) and shorter baseline QRSd (163.5 ± 17.7 ms vs. 169.7 ± 15.1 ms; P = 0.013) than men. Of the 171 patients who completed the follow-up, super-response was observed in 120 (70%), with a higher occurrence in women than men (78.3% vs. 62.5%, P = 0.024). The incidence of death or HFH was numerically lower in women (7.1% Vs 13%, Log-rank P = 0.216). Notably, the super-response showed a significant difference in women compared to men at the same electrocardiography and/or echocardiographic parameters value. Mediation analysis between sex and super-response revealed that LVEDd and pQRSd play an intermediary role, with the mediation proportion of 26.07% and 27.98%, respectively. ConclusionsWomen may derive more benefits from CSP, and pQRSd and LVEDd partly drive this difference.

LEFT BUNDLE BRANCH BLOCK AND ACUTE CORONARY SYNDROME: WHAT IS THE ROLE OF MODIFIED SGARBOSSA–SMITH CRITERIA AND THE WELLENS‘ PATTERN?

Abstract A 55–year–old man presented to the emergency room with intermittent chest pain that started the day before. His medical history included hypertension, and dyslipidemia. The initial electrocardiogram (ECG) showed sinus rhythm (75 bpm) with pre–existing left bundle branch block (LBBB), without modified Sgarbossa–Smith criteria, despite the hyperacute appearance of T waves in V2–V4 (Fig. 1). Additionally, there were alterations in ventricular repolarization in the lateral region, morphologically not fully justifiable by the mentioned conduction delay. Echocardiography revealed normal left and right ventricular systolic function and no valvular abnormalities. Laboratory tests showed a pathological release of myocardial necrosis enzymes, with a typical rise–and–fall curve (10 pg/mL, 100 pg/mL, 200 pg/mL; normal range: 1.7–34.2 pg/mL). Therefore, the patient was admitted to the intensive cardiac care unit (ICCU) with a working diagnosis of non–ST–segment elevation myocardial infarction (NSTEMI). There were no recurrent angina episodes or signs/symptoms of heart failure on physical examination. During hospitalization, ECG and echocardiography were repeated. The follow–up ECG (12 hours after admission) showed persistent LBBB with biphasic T waves in leads V2–V5 with slight negative deflection at the end. This T wave abnormality can be interpreted as Wellens’ ECG Type A (Fig. 3A). The echocardiogram remained unchanged. Consequently, the catheterization lab was activated for urgent coronary angiography. The examination revealed subocclusion of the mid–segment of the left anterior descending artery (LAD). A drug–eluting stent was deployed in the culprit lesion (Fig. 2), restoring coronary flow completely (TIMI Flow 3). The subsequent hospital stay proceeded without complications. The ECG performed before discharge showed a typical LBBB, with normalization of T waves in precordial leads (Fig 3B). The presented case is about ECGs containing a pre–existing LBBB pattern in a patient with chest pain. The modified Sgarbossa–Smith criteria were not met in either the first recorded ECG or the second, whereas Wellens’ signs were detectable. Wellens’ syndrome can be diagnosed in a case of LBBB and help detect a high–grade LAD stenosis even if modified Sgarbossa–Smith criteria are not met.

Abstract 13157: Multivariable ECG Machine Learning is Superior to QRS Duration and Traditional ECG Criteria for Detecting Left Ventricular Hypertrophy in Patients With Left Bundle Branch Block

Introduction: The utility of ECG to diagnose left ventricular hypertrophy (LVH) in patients with left bundle branch block (LBBB) is limited. We sought to compare the diagnostic yield of ECG using (i) QRS duration, (ii) published LVH criteria, and (iii) machine learning (ML) models to detect increased left ventricular mass indexed (LVMi) in the setting of LBBB. Hypothesis: ML is superior to QRS duration and LVH criteria to detect LVH among LBBB. Methods: 12-lead ECGs were processed to reconstruct orthogonal X, Y, Z leads using Kors’s matrix and obtain root-mean-squared (3D) ECG. R wave, S wave and overall amplitudes, voltage-time-integrals (VTIs), and other ECG features were extracted from all ECG leads. ML algorithms [logistic regression (LR), support vector classifier (SVC), decision trees (DT), random forest (RF), gradient boosted machine (GBM) and boosted trees (BT)] were trained to predict increased LVMi (women >95 g/m 2 , men >115 g/m 2 ) from ECG features on a training set of 2668 ECGs with typical LBBB and echocardiogram within 45 days before or after ECG. LVM was calculated using the ASE formula. We obtained ROC AUCs for prediction of increased LVMi by (i) QRS duration, (ii) published LVH criteria, and (iii) ML models in a separate validation set of adults with typical LBBB. Results: Among the validation set of 413 adults (53% women, age 73±12 yr) with LBBB, QRS duration alone had a higher AUC (women 0.657, men 0.703) for diagnosing increased LVMi compared to standard LVH criteria (Table). RF (women 0.688, men 0.738), GBM and DT models had better AUCs than QRS duration alone. Conclusions: In patients with LBBB, QRS duration ≥150 in women and ≥160 in men is a superior predictor of LVH than traditional voltage-based ECG criteria, but ML methods outperform all traditional ECG criteria and QRS duration.

Abstract 16427: Despite Machine Learning Models, QRS Duration Remains the Superior ECG Criterion for Predicting Left Ventricular Dilation in Patients With Left Bundle Branch Block

Introduction: The utility of ECG to diagnose left ventricular (LV) dilation in patients with left bundle branch block (LBBB) is not known. We sought to compare the diagnostic yield of ECG using (i) QRS duration, (ii) published LVH criteria, and (iii) machine learning (ML) models to detect increased left ventricular end diastolic volume indexed (LVEDVi) in the setting of LBBB. Hypothesis: ML is superior to QRS duration and LVH criteria to detect increased LVEDVi among LBBB. Methods: 12-lead ECGs were processed to reconstruct orthogonal X, Y, Z leads using Kors’s matrix and obtain root-mean-squared (3D) ECG. R wave, S wave and overall amplitudes, voltage-time-integrals (VTIs), and other ECG features were extracted from all ECG leads. ML algorithms [logistic regression (LR), support vector classifier (SVC), decision trees (DT), random forest (RF), gradient boosted machine (GBM) and boosted trees (BT)] were trained to predict increased LVEDVi (women >61 mL/m 2 , men >74 mL/m 2 ) from ECG features on a training set of 2668 ECGs with typical LBBB and echocardiogram within 45 days before or after ECG. LVEDV was measured using ASE biplane method of discs. We obtained ROC AUCs for prediction of increased LVEDVi by (i) QRS duration, (ii) published LVH criteria, and (iii) ML models in a separate validation set of adults with typical LBBB. Results: Among the validation set of 413 adults (53% women, age 73±12 yr) with LBBB, QRS duration alone had a higher AUC (women 0.668, men 0.699) for diagnosing increased LVMi compared to standard LVH criteria (Table). The best ML model (RF with overall AUC 0.694) did not substantially outperform QRS duration alone. Conclusions: In patients with LBBB, QRS duration ≥150 in women and ≥160 in men is a superior predictor of LV dilation than traditional ECG-based LVH criteria, with no additional value added by ML methods.

Electrocardiographic prediction of left ventricular hypertrophy in women and men with left bundle branch block - Comparison of QRS duration, amplitude and voltage-time-integral.

Standard ECG criteria for left ventricular (LV) hypertrophy rely on QRS amplitudes. However, in the setting of left bundle branch block (LBBB), ECG correlates of LV hypertrophy are not well established. We sought to evaluate quantitative ECG predictors of LV hypertrophy in the presence of LBBB. We included adult patients with typical LBBB having ECG and transthoracic echocardiogram performed within 3months of each other in 2010-2020. Orthogonal X, Y, Z leads were reconstructed from digital 12‑lead ECGs using Kors's matrix. In addition to QRS duration, we evaluated QRS amplitudes and voltage-time-integrals (VTIs) from all 12 leads, X, Y, Z leads and 3D (root-mean-squared) ECG. We used age, sex and BSA-adjusted linear regressions to predict echocardiographic LV calculations (mass, end-diastolic and end-systolic volumes, ejection fraction) from ECG, and separately generated ROC curves for predicting echocardiographic abnormalities. We included 413 patients (53% women, age 73±12years). All 4 echocardiographic LV calculations were most strongly correlated with QRS duration (all p<0.00001). In women, QRS duration ≥ 150ms had sensitivity/specificity 56.3%/64.4% for increased LV mass and 62.7%/67.8% for increased LV end-diastolic volume. In men, QRS duration ≥ 160ms had a sensitivity/specificity 63.1%/72.1% for increased LV mass and 58.3%/74.5% for increased LV end-diastolic volume. QRS duration was best able to discriminate eccentric hypertrophy (area under ROC curve 0.701) and increased LV end-diastolic volume (0.681). In patients with LBBB, QRS duration (≥ 150 in women and≥160 in men) is a superior predictor of LV remodeling esp. eccentric hypertrophy and dilation.

Diastolic dysfunction inhibits mechanical dyssynchrony in cardiac resynchronization therapy patients: a combined clinical-computational study

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – EU funding. Main funding source(s): This work was supported by the European Union's Horizon 2020 Research and Innovation program under the Marie Skłodowska-Curie grant agreement No. 860745. Background In heart failure patients treated with cardiac resynchronization therapy (CRT), both the presence of typical left bundle branch block (LBBB) mechanics and a relatively preserved diastolic function are associated with better clinical outcomes. However, the mechanistic interaction between both phenomena has never been investigated. Aim In this combined clinical-computational study, we explored the potential interaction between LBBB mechanics and the severity of diastolic dysfunction. Methods In 219 CRT candidates, left atrial pressure (LAP) was retrospectively estimated using the multiparametric guideline approach, where patients were classified into elevated (eLAP, 49%), normal (nLAP, 40%) and undetermined (uLAP, 11%) LAP. nLAP and uLAP were together referred to as non-elevated LAP (non-eLAP, 51%). Typical LBBB mechanical behavior was quantified using two speckle-tracking echocardiography-based indices, being systolic stretch index (SSI) and global myocardial wasted work (GWW). Both indices positively correlate with the mechanical interaction between septal and lateral walls in typical LBBB as previously shown. CRT response was quantified as change of LV end-systolic volume (LVESV) at follow-up (12±6 months) relative to baseline. We used the CircAdapt computer model of the human heart and circulation to investigate the effects of eccentric remodeling and diastolic dysfunction (i.e. myocardial stiffening) on SSI and GWW in virtual hearts with a constant LBBB-like septal-to-lateral conduction delay, i.e. a 25-ms and 75-ms mechanical activation delay of the septum and LV free wall with respect to the right ventricular free wall. Results Before CRT, patients with non-eLAP showed more typical LBBB mechanical behavior (Fig. 1), as suggested by higher SSI and higher GWW compared to patients with non-eLAP (SSI: 4.6±3.2 vs 3.4±3.5 %, P=0.02, GWW: 368±131 vs 309±127 mmHg*%, P=0.03). At follow-up, patients with eLAP showed significantly less LV reverse remodeling compared to patients with non-eLAP (relative decrease of LVESV: 30±26% vs 46±34 P=0.001). Our simulations (Fig. 2) revealed that eccentric remodeling amplifies mechanical dyssynchrony, characterized by increased septal rebound stretch (second row) and increased wasted work (third and bottom rows), while LAP remained normal (top row). In contrast, increasing myocardial stiffness led to elevated LAP (top row), but a pronounced reduction of mechanical dyssynchrony (second, third and bottom rows). Conclusion The presented combination of clinical data and virtual patient simulations revealed that diastolic dysfunction, in particular myocardial stiffening, inhibits mechanical dyssynchrony induced by LBBB. In contrast, eccentric remodeling amplifies the LBBB mechanical substrate. These data further explain why baseline dyssynchrony measures like septal rebound stretch and wasted work are well associated with reverse remodeling and clinical outcome after CRT.

Cardiac Resynchronization Therapy: current guidelines and recent advances beyond drug treatment.

Cardiac resynchronization therapy (CRT) is the therapy of choice for patients with symptomatic systolic heart failure (HF) and left bundle branch block (LBBB), despite optimal medical therapy (OMT). The recently published 2021 European Society of Cardiology (ESC) Guidelines on cardiac pacing and cardiac resynchronization therapy highlight the importance of CRT on top of OMT in HF patients with left ventricular ejection fraction (LVEF) ≤ 35%, sinus rhythm and typical LBBB with QRS duration ≥150ms. In the presence of medically intractable or recurrent after catheter ablation atrial fibrillation (AF), AV nodal ablation as an adjuvant therapy becomes more relevant in patients qualifying for the implantation of a biventricular system. Furthermore, CRT may be considered in cases when increased pacing of the right ventricle is not desirable. However, alternative pacing sites and strategies are currently available, if the CRT is not feasible and effective in patients. However, strategies targeting "multi-sides" or using "multi-leads" have shown superiority over classic CRT. On the other hand, conduction system pacing seems to be a promising technique. Although early results are positive, consistency during the long term is pending. The indication for additional defibrillation therapy (ICD) may occasionally be unnecessary and has to be considered individually. Due to the great development and success of heart failure drug therapy, its positive effect on LV function can lead to enormous improvement. Physicians must await these effects and findings, which hopefully could lead to a relevant LV improvement resulting in a definitive decision against an ICD.

Correction of dyssynchrony by conduction system pacing: results of LEVEL-AT trial

Abstract Funding Acknowledgements Type of funding sources: Public Institution(s). Main funding source(s): Catalan Society of Cardiology; Asociación del Ritmo Cardiaco (Spanish Society of Cardiology). Background Correction of dyssynchrony measured with echo strain, in conduction system pacing (CSP) vs biventricular pacing (BIVP) has not been reported. Objectives Our purpose was to compare echocardiographic dyssynchrony correction and strain improvement during follow-up between CSP and BIVP. Methods A treatment received analysis was performed in patients (n=29 CSP; BIVP 40). Patients were evaluated at baseline (ON and OFF programming) and at 6 and 12 months. All echocardiograms were completed by operators blinded to the type of device implanted. Intraventricular (septal flash), interventricular (difference between left and right ventricular outflow times), and auriculoventricular (diastolic filling time) dyssynchrony, as well as strain parameters (septal rebound, global longitudinal strain (GLS), and Risum pattern (typical left bundle branch block contraction pattern)) were analyzed. Results 32% (22/69) were women; baseline LVEF was 27.5% (7% SD) and left ventricular end-systolic volume (LVESV) 138ml (77ml SD) without differences between groups. At the 12-month follow-up, there were no differences in CSP vs. BIVP in LVEF (45.8% (10% SD) vs. 42.7% (12% SD), p=0.25) and LVESV (81.5 ml (41 ml SD) vs. 101.7 ml (56 ml SD), p=0.08). Longitudinal analyses showed that the improvement of all echocardiographic dyssynchrony parameters over time was similar between groups (p&amp;lt;0.001) (Table 1 and Fig 1A). GLS acute correction significantly correlated with LVEF and LVESV at the 12-month follow-up (Fig 1B). Conclusions CSP and BIVP provided a similar dyssynchrony and strain correction over time. Acute strain correction predicted ventricular remodeling at 12 months follow-up.

Efficacy and safety of zero-fluoroscopy ablation of ventricular arrhythmias originating from the right ventricular outflow tract: Comparison with fluoroscopy-guided ablation without a three-dimensional electroanatomic mapping system.

Radiofrequency catheter ablation is the preferred treatment choice for ventricular arrhythmias (VAs) originating from right ventricular outflow tract (RVOT) in symptomatic patients and is usually performed under fluoroscopy guidance. Zero-fluoroscopy (ZF) ablations using 3D mapping system applied for treatment of various types of arrhythmias are trending and practiced in many centers around the world, but rarely done in Vietnam. The objective of this study was to evaluate the efficacy and safety of zero-fluoroscopy ablation of RVOT VAs, compared with fluoroscopy-guided ablation without a 3D electroanatomic mapping (EAM) system. We conducted a nonrandomized, prospective single-center study including 114 patients with RVOT VAs that had electrocardiographic features of typical left bundle branch block, inferior axis QRS morphology, and a precordial transition ≥ V3, from May 2020 to July 2022. The patients were assigned (without randomization) to two different approaches of either zero-fluoroscopy ablation under the guidance of the Ensite system (ZF group) or fluoroscopy-guided ablation without a 3D EAM (fluoroscopy group) in a 1:1 ratio. After a follow-up time of 5.0 ± 4.9 months and 6.9 ± 9.3 months in the ZF and fluoroscopy groups, respectively, the results showed a higher success rate in the fluoroscopy group than in the complete ZF group (87.3% vs 86.8%), although the difference was not statistically significant. No major complication was noted in both the groups. ZF ablation for RVOT VAs can be done safely and effectively using the 3D electroanatomic mapping system. The results of ZF approach are comparable to that of the fluoroscopy-guided approach without a 3D EAM system.

Electrocardiographic and electrophysiological characteristics of ventricular arrhythmias from the right bundle branch of the moderator band

There are little data on ventricular arrhythmias (VAs) originating from the right bundle branch (RBB) of the moderator band (MB) (MB-RBB VAs) in a cohort of patients. The purpose of this study was to investigate the electrocardiographic and electrophysiological characteristics of MB-RBB VAs. Sixteen patients with MB-RBB VAs and 5 patients with right ventricular (RV) anterior papillary muscle (APM) VAs (RV-APM VAs) were studied under the guidance of intracardiac echocardiography. The MB-RBB VAs group demonstrated a typical left bundle branch block pattern with left superior axis deviation and a narrower QRS complex during VAs (P < .001) as compared with the RV-APM VAs group. Furthermore, the MB-RBB VAs group had a shorter rS interval, a sharper slope of the S wave downstroke without notching in leads V1 and V2, and a shorter r wave duration in lead V2. A leading RBB potential at the target during VAs was observed for all patients in the MB-RBB VAs group, which was also present during sinus rhythm for all patients, except for 2 with RBB block at baseline. Ablation of the leading RBB potential effectively eliminated the arrhythmia. In the RV-APM VAs group, no Purkinje potential at the target was identified in any patient during VAs. QRS morphology of MB-RBB VAs is characterized by a typical left bundle branch block pattern with a relatively narrow QRS complex, short r wave and rS durations, and a sharp S wave downstroke without notching in leads V1 and V2. Mapping and ablation of the leading RBB potential are effective in eliminating VAs.

Fascicular ventricular tachycardia arising from the left side His and its adjacent region: a subset of upper septal idiopathic left ventricular tachycardia.

Fascicular ventricle tachycardia (FVT) arising from the proximal aspect of left His-Purkinje system (HPS) has not been specially addressed. Current study was to investigate its clinical, electrocardiographic, and electrophysiological characteristics. Eighteen patients who were identified as this rare FVT were consecutively enrolled, and their scalar electrocardiogram and electrophysiological data were collected and analysed. The ventricular tachycardia (VT) morphology was similar to sinus rhythm (SR) in eight patients, left bundle branch block type in one patient, right bundle branch block type in seven patients, and both narrow and wide QRS type in two patients. During VT, right-sided His potential preceded the QRS with His-ventricle (H-V) interval of 36.3 ± 12.4 ms, which was shorter than that during SR (-51.4 ± 8.6 ms) (P = 0.002). The earliest Purkinje potentials (PPs) were recorded within 7 ± 3 mm of left-side His and preceded the QRS by 49.1 ± 14.0 ms. Mapping along the left anterior fascicle and left posterior fascicle revealed an antegrade activation sequence in all with no P1 potentials recorded. In the two patients with two VT morphologies, the earliest PP was documented at the same site, and the activation sequence of HPS remained antegrade. Ablation at the earliest PP successfully eliminated the tachycardia, except one patient who developed complete atrial-ventricular block and two patients who abandoned ablations. After at least 12 months follow-up, 15 patients were free from any recurrences. Fascicular ventricle tachycardia arising from the proximal aspect of left HPS was featured by recording slightly shorter H-V interval and absence of P1 potentials. Termination of VT requires ablation at the left-sided His or its adjacent region.

Association of interventricular activation delay with clinical outcomes in cardiac resynchronization therapy

Pacing at sites of longest interventricular delay has been associated with greater reverse remodeling in cardiac resynchronization therapy (CRT). However, the effects of pacing at such sites on clinical outcomes is less well studied. The purpose of this study was to assess the association between interventricular delay and clinical outcomes in CRT patients implanted with quadripolar left ventricular (LV) leads. RALLY-X4 was a registry study of the Acuity X4 quadripolar LV leads. Interventricular delay was measured during unpaced basal rhythm from the right ventricular (RV) lead to the LV lead electrode (E1 to E4) chosen for CRT pacing. Patients were stratified by median RV-LV delay (80 ms) into short and long delay groups; they also were analyzed by multivariable modeling. The primary composite outcome measure was all-cause mortality and heart failure hospitalization (HFH) at 18 months. A total of 581 patients had complete RV-LV delay data. Mean LV ejection fraction was 27%, and 73% had typical left bundle branch block. Predictors of long RV-LV delay included female sex, left bundle branch block, and QRS duration >150 ms. Survival free of the primary outcome at 18-month follow-up was 87% in the long activation delay group compared with 77% in the shortdelay group (P = .0042). Multivariate analysis showed that RV-LV delay was an independent predictor of survival free of HFH (P = .028). Among CRT patients with quadripolar LV pacing leads, longer baseline interventricular activation delay was significantly associated with the composite endpoint of all-cause mortality and HFH.

Introduction to hemodynamic forces by echocardiography

Hemodynamic force (HDF) analysis represents a novel approach to quantify intraventricular pressure gradients, responsible for blood flow. A new mathematical model allows the derivation of HDF parameters from routine transthoracic echocardiography, making this tool more accessible for clinical use. HDF analysis is considered the fluid dynamics correlate of deformation imaging and may be even more sensitive to detect mechanical abnormalities. This has the potential to add incremental clinical value, allowing earlier detection of pathology or immediate evaluation of response to treatment. In this article, the theoretical background and physiological patterns of HDF in the left ventricle are provided. In pathological situations, the HDF pattern might alter, which is illustrated with a case of ST segment elevation myocardial infarction and non-ischemic cardiomyopathy with typical left bundle branch block.

Abstract 13586: In Patients With Left Bundle Branch Block, QRS Duration is a Stronger Predictor of Left Ventricular Hypertrophy and Dilation Than QRS Voltage

Introduction: ECG criteria for left ventricular (LV) hypertrophy in absence of left bundle branch block (LBBB) rely on QRS amplitudes. ECG correlates of LVH in setting of LBBB are not well established. We sought to evaluate quantitative LBBB ECG predictors of echocardiographic LV measurements [LV mass, end-diastolic volume (EDV), end-systolic volume (ESV), ejection fraction (EF)]. Hypothesis: QRS duration (QRSd) is a better predictor of LV hypertrophy than QRS amplitudes. Methods: We included adult patients with typical LBBB having ECG and echocardiogram performed within 3 months of each other in 2010-2020. Digital 12-lead ECGs were processed to reconstruct orthogonal X, Y, Z leads using Kors matrix. Amplitudes and voltage-time-integrals (VTIs) from all 12 leads, X, Y, Z leads and 3D (root-mean-square) ECG, and QRSd were evaluated. We used age, sex and BSA-adjusted linear regressions to predict LV measurements, and separately generated ROC curves for identifying LV abnormalities. Results: We included 413 patients (53% women, age 73±12 yr). Among all the ECG variables, QRSd was most strongly correlated with all 4 LV measurements (all p&lt;0.00001, see Table 1a showing QRSd compared to VTI and amplitude from 3D QRS). Table 1b shows area under ROC curves to identify LV abnormalities. QRS duration ≥150 ms in women had sensitivity 56.3%, specificity 64.4% for LVMi &gt;95 g/m 2 and sensitivity 62.7%, specificity 67.8% for LVEDVi &gt;61 mL/m 2 . QRS duration ≥160 ms in men had a sensitivity 63.1%, specificity 72.1% for LVMi &gt;115 g/m 2 and sensitivity 58.3%, specificity 74.5% for LVEDVi &gt;74 mL/m 2 . Conclusions: In patients with LBBB, QRS duration ≥150 in women and ≥160 in men is a superior predictor of adverse LV remodeling esp. eccentric LV hypertrophy/dilation. The weak correlation of QRS amplitude with hypertrophy may be due to the dominant effect of electrical dyssynchrony on voltage, and the heterogeneous effects of fibrosis, infiltrative cardiomyopathy, epicardial fat and LV dilation.

Non-specific intraventricular conduction delay or atypical LBBB - How to predict acute coronary occlusion?

We describe two patient cases with acute coronary syndrome (ACS) and broad QRS in the acute phase electrocardiogram (ECG). The patients' ECG findings resembled left bundle branch block (LBBB), but with atypical features. Broad QRS not fulfilling the criteria for LBBB or right bundle branch block (RBBB) is diagnosed as non-specific intraventricular conduction delay (NSIVCD). The case report deals with the challenges of predicting acute coronary occlusion in patients with NSIVCD in their acute phase ECG. In one of the cases, the ECG changed from typical LBBB to NSIVCD or atypical LBBB with the development of systolic dysfunction and clinical heart failure.

Predictive Value of Left Atrial Remodeling for Response to Cardiac Resynchronization Therapy.

Response to cardiac resynchronization therapy varies significantly among patients, with one third of them failing to demonstrate left ventricular reverse remodeling after cardiac resynchronization therapy. Left atrial size and function is increasingly recognized as a marker of disease severity in the heart failure population. The aim of this study was to evaluate whether echocardiographic left atrial indices predict left ventricular reverse remodeling after cardiac resynchronization therapy. Ninety-nine cardiac resynchronization therapy candidates were prospectively included in the study and underwent echocardiography before and 3-months after cardiac resynchronization therapy implantation. Cardiac resynchronization therapy response was defined as a 15% relative reduction in left ventricular end-systolic volume. Indexed left atrial volume, left atrial reservoir strain, left ventricular end-diastolic volume, and left ventricular ejection fraction along with other known predictors of cardiac resynchronization therapy response (gender, etiology of heart failure, presence of typical left bundle branch block pattern, QRS duration >150 ms) were included in a multivariate logistic regression model to identify predictors for cardiac resynchronization therapy response. Cardiac resynchronization therapy response occurred in n = 63 (64%) patients. The presence of a typical left bundle branch block (OR 4.2, 95 CI: 1.4-12.1, p = 0.009), QRS duration >150 ms (OR 4.2, 95 CI: 1.4-11.0, p = 0.029), and left atrial volume index (OR: 0.6, 95 CI: 0.4-0.9, p = 0.012) remained the only significant predictors for cardiac resynchronization therapy response after three months. None of the baseline left ventricular parameters showed an independent predictive value. Left atrial size at baseline is an independent predictor and is inversely proportional to left ventricular volumetric reverse remodeling in cardiac resynchronization therapy candidates.

Efficacy of His Bundle Pacing on LVRelaxation and Clinical Improvement in HFandLBBB.

This study aimed to compare acute hemodynamic improvements and responses to His bundle pacing (HBP) and conventional biventricular pacing (BVP). HBP can correct left bundle branch block (LBBB) and may be an alternative cardiac resynchronization therapy (CRT) to BVP. Fourteen consecutive patients with heart failure (HF) and typical LBBB who required CRT were enrolled. The acute hemodynamic responses during HBP and BVP were compared using a micromanometer-tipped catheter inserted into the left ventricle (LV) before CRT. Each configuration was compared with AAI mode. A permanent HBP device was implanted when LBBB correction threshold was≤1.5V at 1.0ms, and remaining patients were treated with BVP. Clinical and echocardiographic improvements were assessed during a 12-month follow-up period. The LV contractile index (positive maximal rate of LV pressure rise [dP/dtmax]) increased similarly during HBP and BVP (18.8% ± 6.4% vs 18.0% ± 10.2%; P = 0.810). LV relaxation indices (negative dP/dtmax and tau) were significantly improved during HBP compared with BVP (negative dP/dtmax: 14.3% ± 5.5% vs 3.1% ± 8.1%; P< 0.001; tau: 7.2% ± 4.3% vs -0.8% ± 8.1%; P = 0.001). Nine (64%) patients received permanent HBP devices, while 5 patients were treated with BVP. The New York Heart Association functional class, LV ejection fraction, LV end-systolic volume, and B-type natriuretic peptide level improved in patients treated with HBP and BVP (all P< 0.05 vs baseline). Patients treated with HBP exhibited earlier and greater improvements of the LV ejection fraction and LV end-systolic volume than did those with BVP. HBP improves systolic function and LV relaxation in patients with HF and LBBB. CRT via HBP produced earlier and greater clinical responses than BVP.

To what extent are perfusion defects seen by myocardial perfusion SPECT in patients with left bundle branch block related to myocardial infarction, ECG characteristics, and myocardial wall motion?

IntroductionWe investigated if uptake pattern on myocardial perfusion SPECT (MPS) in patients with left bundle branch block (LBBB) is related to myocardial fibrosis, myocardial wall motion, and electrocardiography (ECG) characteristics. MethodsTwenty-three patients (9 women) with LBBB, examined with MPS and cardiac magnetic resonance (CMR), were included. Tracer uptake on MPS was classified by visual interpretation as typical LBBB pattern (Defect+, n = 13) or not (Defect−, n = 10) and quantitatively. CMR images were evaluated for wall thickness and for myocardial wall motion both by visual assessment and by regional myocardial radial strain from feature tracking, and for presence and location of myocardial fibrosis. ECGs were analyzed regarding QRS duration and the presence of strict criteria for LBBB. ResultsWall thickness was slightly lower in the septum compared to the lateral wall in Defect+ patients (5.6 ± 1.1 vs 6.0 ± 1.3 mm, P = 0.03) but not in Defect− patients (5.6 ± 1.0 vs 5.6 ± 0.9 mm, P = 0.84). Defect+ patients showed a larger proportion of dyskinetic segments in the septum and hyperkinetic segments in the lateral wall compared to Defect− patients (P = 0.006 and P = 0.004, respectively). Decreased myocardial radial strain was associated with decreased tracer uptake by MPS (R = 0.37, P < 0.001). Areas of fibrosis did not match areas with uptake defect on MPS. No differences in ECG variables were seen. ConclusionThe heterogeneous regional tracer uptake in some patients with LBBB is related to underlying regional myocardial dyskinesia, wall thickening, and wall thickness rather than stress-induced ischemia, myocardial fibrosis, or specific ECG characteristics.

Abstract 13982: Evaluation of Electrocardiographic and Intracardiac Electrogram Characteristics for Response to His-Purkinje Conduction System Pacing in Patients With Left Bundle Branch Block Corrected by His Bundle Pacing

Introduction: His-Purkinje conduction system pacing (HPCSP), including His bundle pacing (HBP) and left bundle branch pacing has been proved to improve clinical outcomes in patients with left bundle branch block (LBBB) and heart failure. However, some patients still remain non-responsive to HPCSP. We aimed to evaluate the effect of electrocardiographic and intracardiac electrogram characteristics for response to HPCSP in patients with typical LBBB which could be corrected by HBP. Methods: Consecutively enrolled patients with typical LBBB and baseline LVEF ≤40% from January 2012 to June 2020 who were able to achieve LBBB correction during HBP and implanted HPCSP. Baseline QRS duration, paced QRS duration, ΔQRSd, H-QRSend and ΔQRSend/H-QRSend were measured during the implantation. A 1-year absolute increase in LVEF≥15% identified super-response to HPCSP. Results: A total of 123 patients were included in the study (mean age 68.2±10.6 years; male 52.0%). Baseline characteristics of patients with ΔLVEF≥15% (N=93) and ΔLVEF&lt;15% (N=30) were comparable except for larger ΔQRSend/H-QRSend (0.42±0.07 vs 0.35±0.08 ms, p&lt;0.001), smaller baseline QRS duration (161.9±15.5 vs 172.3±17.4 ms, p=0.002) and paced QRS duration (100.9±14.9 vs 110.5±13.4 ms, p=0.002) in patients with ΔLVEF≥15%. Receiver-operating characteristic curve analysis demonstrated that a cut-off value of 0.39 for ΔQRSend/H-QRSend presented a sensitivity of 77% and specificity of 76% (AUC=0.776) to predict super-response to HPCSP. At multivariate analysis, larger ΔQRSend/H-QRSend, smaller paced QRS duration and baseline QRS duration remained predictors of super-response after HPCSP. Conclusions: HPCSP delivers favorable echocardiographic response in typical LBBB corrected by HBP. A larger ΔQRSend/H-QRSend, smaller baseline QRS duration and paced QRS duration are associated with a better response after HPCSP. ΔQRSend/H-QRSend is a novel and important predictor of LVEF increase.