Diagnostic Dilemma of Syncope: Esophageal Hiatal Hernia and High-risk Bundle-branch Block.

We herein report a complicated case of recurrent syncope accompanying bundle branch block and hiatal hernia of the esophagus. An 83-year-old woman presented with syncope. Echocardiography visualized the left atrium compressed by an esophageal hiatal hernia, which had potential to decrease the cardiac output. Although she underwent esophageal repair surgery, two months after the surgery, she presented to the emergency department again with complaints of syncope. At the return visit, her face was pale and her pulse rate was 30 beats per minute. Electrocardiography showed complete atrioventricular block. On reviewing the patient's previous electrocardiography findings, we found a record of trifascicular block. This case illustrates the importance of predicting atrioventricular blocks in patients with high-risk bundle-branch blocks. Keeping in mind high-risk bundle-branch blocks will help clinicians avoid anchoring bias due to a striking image masquerading as the true diagnosis.

Electrophysiological study in chagasics with syncope and conduction disorder.

BACKGROUND: Investigation of syncope involves the use of electrophysiological study, particularly in patients with cardiac conduction disorder. There is conflicting evidence about the role of electrophysiological study in patients with Chagas disease. OBJECTIVE: The objective of this study was to evaluate the electrophysiological study findings in patients with Chagas disease and bundle branch block and/or divisional block presenting with syncope. METHODS: This is a retrospective study of patients with Chagas disease and cardiac conduction disorder who underwent electrophysiological study from 2017 to 2021 for the investigation of syncope in a tertiary hospital in São Paulo, Brazil. Those with non-interpretable ECG, known coronary artery disease, and/or other cardiomyopathies were excluded. HV interval and electrophysiological study-induced malignant ventricular arrhythmias data were analyzed. RESULTS: A total of 45 patients (60.2±11.29 years, 57.8% males) were included. The mean HV interval was 58.37 ms±10.68; 22.2% of the studied population presented an HV interval of ≥70 ms; and malignant ventricular arrhythmias were induced in 57.8% patients. The use of beta-blockers and amiodarone (p=0.002 and 0.036, respectively), NYHA functional class≥II (p=0.013), wide QRS (p=0.047), increased HV interval (p=0.02), Rassi score >6.5 (p=0.003), and reduced left ventricular ejection fraction (p=0.031) were associated with increased risk of inducible malignant ventricular arrhythmias. CONCLUSION: More than half of the patients with Chagas disease, syncope, and cardiac conduction disorder have inducible malignant ventricular arrhythmias. Prolonged HV interval was observed in only 20% of population. Wide QRS, prolonged HV, reduced ejection fraction, and higher Rassi score were associated with increased risk of malignant ventricular arrhythmias.

Terminal T-wave concordance is associated with SYNTAX score among left bundle branch block patients suspected of acute coronary syndrome without modified Sgarbossa criteria.

BACKGROUND: Timely and precise diagnosis of ischemic cardiac events based on electrocardiogram is challengeable among patients with Left Bundle Branch Block (LBBB). The present study aimed to assess the correlation between SYNTAX score and terminal T-wave morphologies among LBBB patients suspected of Acute Coronary Syndrome (ACS) without modified Sgarbossa criteria. METHOD: This cross-sectional study was conducted on the LBBB patients suspected of ACS without modified Sgarbossa criteria. Binary logistic regression was used to assess the correlation of ischemic heart disease (IHD, SYNTAX score > 0) and SYNTAX score categories with terminal T-wave morphologies including T-wave direction in lead V6 and terminal T-wave concordance in leads I, V5, and V6. RESULT: This study was done on 93 patients with the mean age of 62.4 ± 9.6 years. More than half of the patients were female (58.1%, 95% CI: 47.4% to 68.2%). Among the participants with IHD, the SYNTAX score categories were correlated to discordant terminal T-wave in leads I, V5, and V6 (OR = 5.71, 95% CI: 1.04 to 31.28, p = 0.04). CONCLUSION: Among the LBBB patients with acute ischemic cardiac events without modified Sgarbossa criteria, those with discordant terminal T-waves in leads I, V5, or V6 had higher SYNTAX scores and might require more invasive coronary revascularization techniques such as Coronary Artery Bypass Graft (CABG) surgery.

Conduction Disturbances and Arrhythmia Risk After Septal Reduction Therapy with Alternative Agents: A Pilot Study with EVOH-DMSO and Systematic Review.

OBJECTIVE: Surgical septal myectomy and alcohol septal ablation are recommended treatment modalities for alleviating Left ventricular outflow tract (LVOT) gradient in obstructive HCM. Alcohol septal ablation offers advantages over surgery in many ways. However, it is associated with some life-threatening complications. For this purpose, our center used alternative agents for septal artery embolization. This study compared and evaluated conduction system defects and arrhythmia risk after EVOH-DMSO septal ablation with other alternative agents and alcohol septal ablation. METHODS: Twenty-five patients who received septal reduction therapy with EVOH-DMSO were analyzed retrospectively, and all non-alcoholic agent's septal ablation studies were systematically reviewed and compared. RESULTS: Twenty-five patients (52% female; mean age: 55.8 ± 17.1) with symptomatic obstructive HCM were enrolled. The Peak LVOT gradient was significantly reduced after the procedure (68 vs. 20 mmHg; P <0.001). During the 12-month follow-up, no mortality occurred. The complete atrioventricular block was noted in 2 (8%) patients. The incidence of right bundle branch block (RBBB) increased after the procedure (pre-procedural 2 patients (8%), post-procedural 9 patients (36%) P = 0.002). On ECG and Holter monitorization, no sustained ventricular tachyarrhythmia occurred during follow-up, and no change was found in the frequency of atrial fibrillation. We systematically compared EVOH-DMSO to other non-alcohol agents, and we found that EVOH-DMSO can cause conduction system problems more commonly than other non-alcohol agents. CONCLUSION: EVOH-DMSO could cause conduction system problems more common than other non-alcohol agents but less than alcohol septal ablation.

Transthoracic echocardiography for arrhythmic mitral valve prolapse: Phenotypic characterization as first step.

Mitral valve prolapse (MVP) is the most frequent valvulopathy with a prevalence of 1.2%-2.4% in general population and it is characterized by a benign course. Although it can be associated with some complications, ventricular arrhythmias (VA) and sudden cardiac death (SCD) as ultimate expressions, are the most worrying. The estimated risk of SCD in MVP is between 0.2% and 1.9% per year including both MVP patients with left ventricular (LV) dysfunction due to severe MR and MVP patients without significant MR. The latter ones constitute a particular phenotype called "malignant MVP" characterized by bileaflet myxomatous prolapse, ECG repolarization abnormalities and complex VAs (c-VAs) with polymorphic/right bundle branch block morphology (RBBB) and LV fibrosis of the papillary muscles (PMs) and inferobasal wall secondary to mechanical stretching visualized as late gadolinium enhancement (LGE) areas by cardiac magnetic resonance (CMR). In MVP, the first diagnostic approach is transthoracic echocardiography (TTE) that defines the presence of mitral annular disjunction (MAD) which seems to be associated with "arrhythmic MVP" (AMVP). From an ECG point of view, AMVP is characterized by frequent premature ventricular contractions (PVCs) arising from one or both PMs, fascicular tissue, and outflow tract, as well as by T-wave inversion in the inferolateral leads. The aim of the present paper is to describe TTE red flags that could identify MVP patients at high risk to develop complex arrhythmias as supported by the corresponding findings of LGE-CMR and anatomy studies. TTE could be a co-partner in phenotyping high-risk arrhythmic MVP patients.

Prevalence of major electrocardiographic abnormalities in patients with hypertension in a primary care clinic in Hong Kong.

BACKGROUND: Hypertension is strongly associated with cardiovascular events. Studies have shown that electrocardiographic (ECG) abnormalities were associated with increased risks for cardiovascular events. However local data is limited. The objectives of this study were: (1) to determine the prevalence of major electrocardiographic abnormalities in patients with hypertension in primary care in Hong Kong, and (2) to determine the association of major electrocardiographic abnormalities with patients' socio-economical background, cardiovascular disease and cardiovascular risk factors. METHODS: This was a cross-sectional study. Subjects were hypertensive patients aged between 18 and 80 who were enrolled in the Risk Assessment and Management Programme (RAMP) in a general outpatient clinic in Hong Kong. Outcome measures were prevalence of probable ischaemic heart disease (IHD), complete left bundle branch block (LBBB), left ventricular hypertrophy (LVH) and atrial fibrillation (AF) in patients with hypertension. The Pearson Chi-square test, independent t-test and Mantel-Haenszel test were used to measure the association between socioeconomic characteristics and cardiovascular risk factors, and ECG abnormalities. RESULTS: 504 hypertensive patients aged 18-80 were recruited in a general outpatient clinic. 6.3% had probable IHD, 0.4% had complete LBBB, 4.0% had LVH and 1.0% had AF. Probable IHD was associated with smoking (P = 0.032), hypercholesterolaemia (P = 0.037) and higher 10-year CV risk (P = 0.04). Complete LBBB was associated with smoking (P = 0.021) and hypercholesterolaemia (P = 0.022). LVH was associated with male gender (P = 0.001) and longer duration of hypertension (P = 0.035). AF was not significantly associated with any of the clinical or sociodemographic parameters. CONCLUSIONS: This study showed that a significant proportion of patients with hypertension at the primary care setting in Hong Kong had probable ischaemic heart disease, left ventricular hypertrophy and atrial fibrillation. This finding is consistent with both overseas data and historic data in Hong Kong. The detection of electrocardiographic abnormalities is helpful in hypertension management by improving risk stratification.

Impact of pre-existing right or left bundle branch block on patients undergoing surgical aortic valve replacement.

OBJECTIVES: Contemporary data on the prognostic impact of pre-existing left or right bundle branch block on clinical outcomes after aortic valve (AV) replacement are limited. The aim of this study was to evaluate the impact of pre-existing bundle branch block on clinical outcomes in patients undergoing AV replacement. METHODS: Data from patients who underwent AV replacement surgery between 2004 and 2020 were obtained from our departmental database. RESULTS: Of the 2704 study patients, 203 (7.5%) had pre-existing bundle branch block and 2501 (92.5%) had normal atrioventricular conduction. The mean age was 68 (13) years, 1697 (63%) were male and 683 (25%) had a unicuspid or bicuspid AV. The in-hospital mortality rate was higher in patients with pre-existing bundle branch block compared to those without on admission (5.9% vs 2.9%, P = 0.032), and more frequent in patients with left compared with right bundle branch block (11.9% vs 4.3%, P = 0.003). New pacemaker implantation was most frequent in those patients with pre-existing left bundle branch block, followed by right and no bundle branch block on admission (28.6% vs 7.5% vs 2.8% respectively, P < 0.001; odds ratio 4.96 95% confidence interval 2.96-8.08, P < 0.001). The 10-year cumulative survival rate was lower in patients with bundle branch block compared with patients with no bundle branch block (76.8% vs 82.8%, log-rank P < 0.001; hazard ratio 0.73, confidence interval 0.54-0.99, P = 0.042). CONCLUSIONS: This study indicates that patients with pre-existing bundle branch block have a higher incidence of pacemaker implantation and all-cause mortality after AV replacement compared with patients without a conduction disturbance.

Postoperative Coronary Artery Spasm After Mitral Valve Replacement and Cox-Maze IV Procedure: A Case Report.

BACKGROUND: Few cases have been reported about coronary artery spasm after a mitral valve replacement and concomitant Cox-Maze IV procedure. We report the case of an adult male who developed right coronary artery (RCA) spasm after a mitral valve replacement with tricuspid valve repair and Cox-Maze IV procedure. CASE REPORT: A 66-year-old male, complaining of progressive exertional shortness of breath, was diagnosed with severe mitral stenosis, moderate tricuspid regurgitation, complete right bundle branch block, and persistent atrial fibrillation (AF) in our clinic. The patient underwent elective mitral valve replacement, tricuspid valve repair, and Cox-Maze IV procedure. Four hours after surgery, a 12-lead electrocardiogram (ECG) showed progressive elevation of ST-segment in the avF and III leads and Troponin-T was over 7000 pg/mL. After one hour, Troponin-T increased to over 10000 pg/mL, and ECG still showed persisted ST-segment elevation in inferior leads. Emergent angiography was performed, and intra-coronary administration of nitroglycerin completely relieved the spasm. CONCLUSION: Potential risks of coronary injury after valvular surgery and Cox-Maze IV procedure need further aggressive investigation and postoperative ischemia should prompt an emergent coronary angiography to identify the cause and apply immediate therapy.

Manejo de la insuficiencia cardiaca con estimulación hisiana en bloqueo de rama derecha: reporte de caso / Management of heart failure with His bundle pacing in right bundle branch block: case report

Resumen La terapia de resincronización cardiaca mediante estimulación hisiana ha demostrado ser efectiva en pacientes con bloqueo de rama izquierda del haz de His e insuficiencia cardiaca. Paciente masculino, con 47 años de edad, con insuficiencia cardiaca, fracción de expulsión del 17% y miocardio dilatada idiopática, electrocardiograma en ritmo sinusal, bloqueo auriculoventricular de 1.er grado, intervalo PR 400 ms, bloqueo completo de rama derecha del haz de His, bloqueo del fascículo anterior de la rama izquierda del haz de His, duración del QRS 200 ms. Se decidió realizar estimulación selectiva del haz de His. La resincronización cardiaca biventricular convencional en pacientes con presencia de bloqueo completo de la rama derecha del haz de His no está indicada debido a la pobre respuesta al tratamiento. La estimulación hisiana permite reclutar la rama bloqueada y reestablecer la conducción a través de ella, de tal forma que, en ausencia de necrosis, se logre sincronía biventricular. En el caso presentado el reclutamiento de la rama derecha mediante estimulación hisiana se reflejó en el restablecimiento de la sincronía biventricular, medida por rastreo de marcas (speckle tracking) e incremento significativo de la fracción de expulsión del ventrículo izquierdo del 17 al 36.6%, con un incremento absoluto del 19.6%.

Abstract Cardiac resynchronization therapy has proven to be an effective therapy in patients with left bundle branch block and heart failure. Male, 47 years old, heart failure with a left ventricle ejection fraction of 17%, idiopathic heart failure. ECG with sinus rhythm, 1st degree AV block, PR 400 ms, complete right bundle branch block, anterior hemi-fascicle of the left bundle of His, and QRS duration 200 ms. We decided to perform a selective His bundle pacing. In patients with right bundle branch block the biventricular cardiac resynchronization is not indicated due to low treatment response. His bundle pacing allows recruiting the blocked branch and restoring conduction throughout it, therefore, in the absence of necrosis the biventricular synchrony is achieved. We presented a case of His bundle pacing with recruitment of the right bundle branch, which reestablish biventricular synchrony measured by speckle tracking, and with a significant increase of the left ventricle ejection fraction from 17 to 36.6%, with an absolute increase of 19.6%.

Electrocardiogram Criteria to Diagnose Cardiac Amyloidosis in Men With a Bundle Branch Block.

Diagnosing cardiac amyloidosis is challenging and requires a high index of suspicion in patients with an increased left ventricular wall thickness (LVWT). Low QRS voltage on electrocardiogram (ECG) has been regarded as the hallmark ECG finding in cardiac amyloidosis; however, the presence of low voltage can range from 20-74% and the voltage/mass ratio carries a greater diagnostic accuracy than QRS voltage alone. Patients with cardiac amyloidosis can have conduction system infiltration and this may result in a BBB. Therefore, the ECG or mass/voltage criteria established for patients with a narrow QRS in the diagnosis of cardiac amyloidosis may not be applicable in patients with a BBB. We sought to identify criteria to aid in the diagnosis of cardiac amyloidosis in patients with increased LVWT on echocardiogram and with a BBB on ECG. We calculated the total QRS score/LVWT, limb lead QRS score/LVWT, R in lead aVL/LVWT, R in lead I/LVWT, and Sokolow index/LVWT. In patients with an increase in LVWT and BBB, total QRS voltage that is indexed to wall thickness can help distinguish between patients with increased wall thickness who have cardiac amyloidosis from those who have LVH related to a pressure overload state. A unique index of Total QRS Score/LVWT is the best predictor of cardiac amyloidosis with a cutoff value of 92.5 mV/cm which is 100% sensitive and 83% specific for the diagnosis of cardiac amyloidosis. This may be a useful screening tool in patients with an increased wall thickness to raise diagnostic suspicion for cardiac amyloidosis.

Sgarbossa Criteria in Left Bundle Branch Block in a Hypertensive Emergency, a Case Report

Abstract Left bundle branch block and hypertensive emergency are very common conditions in clinical cardiovascular and emergency practice. Hypertensive emergency encompasses a spectrum of clinical presentations in which uncontrolled blood pressure leads to progressive end-organ dysfunction. Suspected acute myocardial infarction in the setting of a left bundle branch block presents a unique diagnostic and therapeutic challenge to the clinician. The diagnosis is especially difficult due to electrocardiographic changes caused by altered ventricular depolarization. However, reports on the use of the Sgarbossa's criteria during the management of hypertensive emergency are rare. My current case is a hypertensive emergency patient with acute chest pain and left bundle branch block. Sgarbossa's criteria were initially very weak and, over time, became highly suggestive of acute ST-segment elevation myocardial infarction. Interestingly, chest pain increased as the Sgarbossa's diagnostic criteria were met. Here, we present a case of developing ST-segment elevation myocardial infarction with left bundle branch block that is indicating for thrombolytic therapy. Thrombolytic therapy was strongly indicated because of a higher developing of Sgarbossa criteria scoring. Thus, the higher Sgarbossa criteria scoring in the case was the only indication for thrombolytic. Therefore, how did Sgarbossa criteria developing during the course of the case to indicating the need for thrombolytic therapy?

Prognostic value of regadenoson stress myocardial perfusion imaging in patients with left bundle branch block or ventricular paced rhythm.

BACKGROUND: Vasodilator stress myocardial perfusion imaging (MPI) is the provocative test of choice in patients with left bundle branch block (LBBB) or ventricular paced (V-paced) rhythm. The prognostic value of regadenoson SPECT myocardial perfusion imaging (MPI) in these patients has not been studied. METHODS AND RESULTS: We conducted a retrospective cohort study of 562 patients [mean age, 69 ± 11 years; men, 53.3%] with LBBB (50.7%) or V-paced rhythm (49.3%) who underwent regadenoson stress SPECT-MPI. There were 321 (57.1%) subjects with abnormal MPI and 192 (34.2%) with myocardial ischemia. During a mean follow-up of 2.5 ± 1.9 years, 39 (6.9%) patients had a major adverse cardiac event (MACE), defined as cardiac death or myocardial infarction. The annualized MACE rate in patients with normal MPI was 0.9% (LBBB, 0.8%; V-paced, 1.0%). There was a significant stepwise increase in MACE rates with increasing burdens of perfusion abnormality (P < 0.001) and myocardial ischemia (P = 0.001). Increased risk with abnormal MPI [adjusted hazard ratio, 4.26; P = 0.001] and myocardial ischemia [adjusted hazard ratio, 2.70; P = 0.003] was independent of and incremental to important clinical covariates. Abnormal MPI and myocardial ischemia predicted MACE similarly in both LBBB and V-paced subgroups (interaction P values > 0.05). CONCLUSION: In patients with LBBB and V-paced rhythm, regadenoson stress SPECT-MPI provides independent and incremental prognostic value in predicting adverse cardiac events.

Pre-procedural pacing bias among transcatheter aortic valves with higher post-procedure pacing rates: evidence from the UK TAVI Registry.

Rates of permanent pacemaker (PPM) implantation following transcatheter aortic valve implantation (TAVI) are higher than following surgery and are dependent on patient factors and valve type. There is an increasing trend towards pre-emptive PPM insertion in patients with significant conduction disease prior to TAVI. We report results from the British Cardiovascular Intervention Society (BCIS) on pre- and post-procedural PPM implantation in the TAVI population. All centres in the United Kingdom performing TAVI are required to submit data on all TAVI procedures to the National database which are then reported annually. During 2015, there were 2373 TAVI procedures in the UK. 22.4% of TAVI patients had a PPM implanted either pre-procedure (including the distant past), or during the in-hospital procedural episode. Of these, 7.9% were pre-procedure and 14.5% post-procedure. Overall PPM rates were Edwards Sapien (13.5%), Medtronic CoreValve (28.2%) and Boston Lotus (42.1%; p < 0.01). Pre-procedure pacing rates were Edwards Sapien (6.0%), Medtronic CoreValve (9.1%) and Boston Lotus (12.3%; p < 0.01). Pre-procedural pacing rates for the Boston Lotus valve have risen year-on-year from 5.8% (2013) to 8.6% (2014) to 12.3% (2015). The UK TAVI Registry demonstrates a pre-procedural permanent pacing bias amongst patients receiving transcatheter valves with higher post-procedure pacing rates. Pre-emptive permanent pacing is likely to be responsible for this difference.

Severe myocardial ischemia in a patient with diabetes mellitus and left bundle branch block.

We present the case of a 69-year-old woman with diabetes mellitus, left bundle branch block, and obesity who develops cardiogenic shock after undergoing myocardial perfusion imaging and diagnostic left heart catheterization, but prior to coronary revascularization. This case highlights the risk of cardiac decompensation awaiting surgery in patients with multivessel coronary artery disease. It also emphasizes the subtleties involved in imaging patients with diabetes mellitus and left bundle branch block, as well as the risk of developing complete heart block in the setting of ischemia with underlying conduction disease.

[Transcatheter aortic valve implantation and conduction disturbances]. / Implantation percutanée de valve aortique et troubles conductifs.

Transcatheter aortic valve implantation (TAVI) is currently becoming the treatment of choice for patients with calcific aortic stenosis. Despite several technical improvements, the incidence of conduction disturbances has not diminished and remains TAVI's major complication. These disturbances include the occurrence of left bundle branch block and/or high-grade atrioventricular block often requiring pacemaker implantation. The proximity of the aortic valve to the conduction system (conduction pathways) accounts for the occurrence of these complications. Several factors have been identified as carrying a high risk of conduction disturbances like the presence of pre-existing right bundle branch block, the type of valve implanted, the volume of aortic and mitral calcifications, the size of the annulus and the depth of valve implantation. Left bundle branch block is the most frequent post TAVI conduction disturbance. Whereas the therapeutic strategy for persistent complete atrioventricular block is simple, it becomes complex in the presence of fluctuating changes in PR interval and left bundle branch block duration. The QRS width threshold value (150-160 ms) indicative of the need for pacemaker implantation is still being debated. Although there are currently no recommendations regarding the management of these conduction disturbances, the extension of TAVI indications to patient at low surgical risk calls for a standardization of our practice. However, a decision algorithm was recently proposed by a group of experts composed of interventional cardiologists, electrophysiologists and cardiac surgeons. There are still uncertainties about the appropriate timing of pacemaker implantation and the management of new onset left bundle branch block.

Malignant Arrhythmia with Variants of Desmocollin-2 and Desmoplakin Genes.

Malignant arrhythmia is a fast cardiac arrhythmia that can lead to a hemodynamic abnormality within a short time, most of which is ventricular tachycardia or ventricular fibrillation (VF), which should be managed in time. Both organic and nonorganic cardiac diseases have the potential to cause malignant arrhythmia. We report a noteworthy case of malignant arrhythmia in a teenager during exercise. Transthoracic echocardiography, cardiac magnetic resonance (CMR), electrophysiological study, magnetic resonance imaging of the brain, electroencephalography, chest X-ray, and blood tests were all normal. Twelve-lead electrocardiography showed incomplete right bundle branch block (IRBBB). Two heterozygous missense variants of the desmocollin-2 gene (DSC2, c.G2446A/p.V816M) and desmoplakin gene (DSP, c.G3620A/p.R1207K) were detected in the peripheral blood of this teenager and his father by genetic testing, which encoded a desmosomal protein that was related to arrhythmogenic right ventricular cardiomyopathy (ARVC). In these two rare variants, DSC2 V816M has been reported but uncertain significance, whereas DSP R1207K is never reported. Therefore, the two site variants in DSC2 and DSP genes are likely to become a new research focus for diagnosis and treatment of ARVC in the future. Meanwhile, this report emphasizes that, in addition to a standard set of laboratory tests and examinations, genetic testing may be useful for analyzing the causes of malignant arrhythmia.

Relationships between electrical and mechanical dyssynchrony in patients with left bundle branch block and healthy controls.

BACKGROUND: Abnormal electrical activation may cause dyssynchronous left ventricular (LV) contraction. In this study, we characterized and analyzed electrical and mechanical dyssynchrony in patient with left bundle branch block (LBBB) and healthy controls. METHODS: Myocardial perfusion imaging (MPI) data from 994 patients were analyzed. Forty-three patient fulfilled criteria for LBBB and 24 for controls. Electrical activation was characterized with vector electrocardiography (VECG) and LV function including mechanical dyssynchrony with ECG-gated MPI phase analysis. RESULTS: QRS duration (QRSd; r = 0.69, P < .001) and a few other VECG parameters correlated significantly with phase bandwidth (phaseBW) representing mechanical dyssynchrony. End-diastolic volume (EDV; r = 0.59, P < .001), ejection fraction and end-systolic volume correlated also with phaseBW. QRSd (ß = 0.47, P < .001) and EDV (ß = 0.36, P = .001) were independently associated with phaseBW explaining 55% of its variation. Sixty percent of patients with LBBB had significant mechanical dyssynchrony. Those patients had wider QRSd (159 vs 147 ms, P = .013) and larger EDV (144 vs 94 mL, P = .008) than those with synchronous LV contraction. Cut-off values for mechanical dyssynchrony seen in patients with LBBB were QRSd ≥ 165 ms and EDV ≥ 109 mL. CONCLUSIONS: Despite obvious conduction abnormality, LBBB is not always accompanied by mechanical dyssynchrony. QRSd and EDV explained 55% of variation seen in phaseBW. These two parameters were statistically different between LBBB cases with and without mechanical dyssynchrony.