Left Bundle Branch Block Pattern Research Articles

Cardiopulmonary Exercise Test in Myocardial Ischemia Detection

Exercise electrocardiography has low sensitivity for detection of myocardial ischemia. However, when combined with cardiopulmonary exercise testing (CPEX), the sensitivity and specificity of ischemia detection improves significantly. CPEX offers unique advantages over imaging techniques in tricky situations such as balanced ischemia. Early abnormal oxygen uptake would point toward profound coronary stenosis that could be missed in perfusion imaging. CPEX could be an invaluable tool in asymptomatic left bundle branch block pattern, without exposing patients to the risks of computerized tomography or invasive coronary angiography. Normal oxygen uptake curves would rule out significant coronary stenosis as the cause of left bundle branch block pattern. Elseways, abnormal oxygen uptake in patients with normal coronary arteries could indicate microvascular angina. Furthermore, exercise capacity is an excellent predictor of cardiovascular risk in those with and without heart disease. Using two clinical cases we introduce the concept of gas-exchange and hemodynamic changes encountered in ischemic heart disease.

Ventricular Pre-excitation Causing Left Ventricular Dysfunction Partially Reverted After Ablation of the Accessory Pathway

Ventricular pre-excitation is one of the rarest causes of cardiomyopathy induced or mediated by arrhythmia. Right accessory pathways, specifically with left bundle branch block pattern, can cause ventricular dysfunction, since abnormal ventricular activation resulting from anterograde atrioventricular conduction can cause atrioventricular, interventricular, and intraventricular dyssynchrony, with asynchronous contraction of the ventricular wall and mitral regurgitation. An asymptomatic patient, with ventricular pre-excitation with left bundle branch block and moderate ventricular dysfunction at echocardiography, was described. The electrophysiological study demonstrated an accessory route of anterior location and with an anterograde refractory period of 600 ms, successfully performing radiofrequency ablation and substantial improvement of ventricular function.

Ventricular Pre-excitation Causing Left Ventricular Dysfunction Partially Reverted After Ablation of the Accessory Pathway

A pré-excitação ventricular é causa rara de cardiomiopatia induzida ou mediada por arritmias. As vias acessórias à direita, especificamente com padrão de bloqueio de ramo esquerdo, podem causar disfunção ventricular pela ativação ventricular anormal resultante da condução anterógrada pela via acessória, por causar dessincronismo atrioventricular, interventricular e intraventricular, com contração assíncrona da parede ventriculare regurgitação mitral. Foi descrita uma paciente assintomática, com eletrocardiograma exibindo pré-excitação ventricular, blo-queio do ramo esquerdo e disfunção ventricular sistólica moderada. Estudo eletrofisiológico demonstrou via acessória de localização anterior e com período refratário anterógrado de 600 ms, realizando-se ablação por radiofrequência com sucesso e significativa melhora da função ventricular.

P1733 Late onset of arrhytmogenic cardiomyopathy, unmasked by myocarditis - when multimodality imaging solves the puzzle

Abstract Introduction Arrhythmogenic cardiomyopathy (AC) is a genetic disease, associated with arrhythmic sudden death in young people. Since inflammation might be also present, differential diagnosis with myocarditis is necessary. We present a challenging case, initially diagnosed with ventricular tachycardia (VT) and acute myocardial infarction (AMI), in which multimodality imaging changed the initial diagnosis. Clinical case. A 68-year old woman with dyslipidaemia and hypertension was admitted with chest pain, negative T waves in anterior leads, epsilon wave in V1, V2 (Fig. A, B), negative troponin I (TpI), and elevated NT-proBNP (342 ng/ml). One month before, she was hospitalized for a monomorphic VT with left bundle branch block (LBBB) pattern, with hemodynamic instability, cardioverted electrically to sinus rhythm. Increased TpI suggested an AMI. She recalls an episode of flu with high fever (39°C) before admission. At current admission, transthoracic echo (TTE) revealed LVEF 52%, severe lateral wall hypokinesia, severe RV dysfunction with fractional area change 23%, and TAPSE 15 mm. Coronary angiography excluded significant lesions. Speckle tracking echo(STE) revealed patchy areas of decreased LV myocardial deformation (Fig. C), and decreased basal deformation in RV free wall(Fig. D). Cardiac magnetic resonance (CMR) revealed LVEF 59%, lateral and septal wall hypokinesia, late gadolinium enhancement (LGE) in mid-ventricular lateral wall and interventricular septum (Fig. F), with correspondent increased extracellular volume (ECV) >30%, increased native T1 time, increased T2 mapping, and small pericardial effusion (7 mm); RV was dilated (diastolic volume 107 ml/m2 and systolic volume 69 ml/m2), with severely decreased RV ejection fraction (RVEF) of 35%, hypokinesia of free wall, dyssynchronous contractions, and microaneurysms (Fig. E, F). Diagnosis was concluded for AC with delayed onset, revealed by an acute myocarditis. Betablocker, ACEI, and implantable cardioverter defibrillator (ICD) in secondary prevention were decided. Relatives were screened for the presence of AC. Patient`s daughter presented 8000 isolated monomorphic ventricular ectopic heart beats with LV origin, no echo signs, but incipient signs of AC on CMR (increased ECV on T1 mapping in 7 LV myocardial segments, without LGE). Discussion We presented a rare case of late arrhythmic onset of AC in a patient, in which the first aetiology of VT was considered to be ischaemic. VT with LBBB morphology can be caused by myocarditis, AMI, or AC. Similarly, epsilon wave with negative T waves in precordial leads may have multiple aetiologies. In our case, multimodality imaging approach excluded AMI and suggested an inflammatory cause for VT. CMR allowed the identification of morphologic condition AC and the trigger condition of myocarditis. Conclusions Our case highlights the importance of a multimodality imaging approach in diagnosing AC and myocarditis, for a correct and complete management. Abstract P1733 Figure.

Synthesis of Standard 12-lead Electrocardiograms from Asynchronous Bipolar Leads

We describe a 41-year-old man with a prior history of myocardial infarction, whose surface 12-lead electrocardiogram did not show typical left bundle-branch block pattern or wide QRS complex. However, electrophysiological study showed distinct left ventricular electrical conduction delays. The surface 12-lead electrocardiogram modified to the paper at 50 mm/s and double standard (20 mm equals 1 mV) revealed obvious notches of the terminal forces of the QRS in leads II, III, aVL, aVF, V3, V4, V5, and V6, these might be partially consistent with left ventricular electrical conduction delay in the scar lesion of the infero-posterior of the ventricle.

Longitudinal dissociation and transition in thickness of the His-Purkinje system cause various QRS waveforms of surface ECG under His bundle pacing: A simulation study based on clinical observations.

His bundle pacing (HBP) is a feasible and reliable alternative to conventional right ventricular pacing (RVP), but associated ECG (electrocardiogram) changes have not been well-studied. This study aimed to determine the mechanisms underlying ECG changes associated with HBP using patient-specific multiscale heart simulations. ECGs were recorded in two patients who were treated by HBP under a native rhythm and HBP at high and low voltages. We created patient-specific multiscale simulation heart models of these patients and performed ECG simulation under these conditions. Using these results and detailed information on the electrical field around the pacing lead, we investigated mechanisms underlying the observed ECG changes. Heart simulations successfully reproduced ECGs under a native rhythm for both cases. In case 1, nonselective HBP produced a left bundle branch (LBB) block pattern, which was reproduced as a selective right bundle branch (RBB) pacing. However, in case 2, ECG under nonselective HBP showed an RBB block pattern, which could not be reproduced by the commonly used framework. Findings on the electrical field and anatomy of the His bundle and its branches suggested that longitudinal dissociation of the His bundle and transition of thickness in the stem of the LBB caused a conduction delay in the RBB to produce these ECG changes in this patient. Variations in the anatomy of the His bundle and its branches may underlie the diverse ECG responses to HBP. These variations should be taken into account when performing this therapy.

Value of Fragmented QRS Complex on 12-lead ECG as A Valuable Marker of Myocardial Damage of CAD Patients

Background: Presence of Fragmented QRS (fQRS) on a 12-lead Electrocardiogram (ECG) was associated with various cardiac diseases. This phenomenon could represent as an electrical disruption of conduction system following myocardial damage due to coronary artery disease (CAD). We aimed to investigate the value of fQRS to detect the myocardial scar as detected by SPECT Myocardial Perfusion Imaging (MPI).
 Methods: A cross-sectional study of patients with clinical diagnosis of CAD who underwent Cardiac SPECT. The fQRS defined as morphologies of QRS wave (<120 ms), which included an additional R wave (R’), notching in the nadir of S wave, or >1 R’ (fragmentation) in 2 contiguous leads, corresponding to a major coronary artery territory. Pathological Q wave, paced rhythm, typical right or left bundle branch block pattern with QRS duration of ≥ 120 ms were excluded. MPI was interpreted by visual analysis and semi-quantitative scores on 17-segment assessment according to standard nomenclature.
 Results: Total of 72 patients (49 males, mean age 54.7 ± 9.8 years). fQRS was found in 46 patients (64%). The frequency of myocardial scar was significantly higher in patients with fQRS (89% vs. 15%, p<0.05). Sensitivity, specificity, positive and negative predictive value of fQRS for any of myocardial scar as detected by SPECT analysis were 91%, 81%, 89%, and 84%, respectively. From regional scar analysis, fQRS has sensitivity and specificity of 87% and 90% for anterior wall, 76% and 80% for inferior wall, 73% and 79% for lateral wall. LVEF was significantly lower in patients with fQRS (36.9±2.1 vs. 53.2±2.2, p< 0.05).
 Conclusion: The fragmented QRS could serve as a novel ECG marker to detect and localize the myocardial damage in CAD patients. Regional fQRS patterns denote the presence of regional myocardial scar and are a valuable diagnostic marker of CAD with good sensitivity and specificity.
 Keywords: fragmented QRS, SPECT

Improvement of abnormal systolic motion of the interventricular septum with cardiac resynchronization therapy.

There is no consensus in the literature regarding what is the responsible mechanism of left ventricular dyssynchrony; septal dyskinesia or late movement of left ventricle (LV) lateral wall. We aim to evaluate the abnormal systolic motion in each myocardial segment and the improvement of LV systolic function with pulsed tissue Doppler imaging (TDI) in patients undergoing cardiac resynchronization therapy (CRT) with left bundle branch block (LBBB). A total of 26 patients undergoing CRT implantation with LBBB, wide QRS duration (≥120ms), and low ejection fraction (EF) (<35%) were included. Pulsed TDI was taken from apical 4-chamber view and parasternal short axis view (PSAX). All echocardiographic parameters were measured when CRT is on and off. Systolic ejection time (ET) of anteroseptal and posterolateral wall of LV in PSAX was statistically significantly longer in CRT on group (321.6±62.7vs 237.5±59.3 ms, P<.001; 323.9±58.0vs 289.4±43.7 ms, P=.015, respectively). In apical 4-chamber view, septal annulus systolic ET is significantly longer in CRT on group than CRT off group (315.8±57.2vs 287.3 ± 42.2, P=.014). Also, there was a strong correlation between systolic ET of the septum in PSAX with aortic velocity time integral (VTI), QRS duration and EF (r=.587, P=.002; r=.479, P=.013; r=.440, P=.025; respectively). Circumferential contraction of septal myocardial fibers is improved with CRT and it is strongly correlated with increase of aortic VTI and shortening of QRS duration. These findings predict the deterioration of septal contraction as the main mechanism in patients with LBBB pattern and, CRT may improves myocardial contraction by correcting septal systolic motion.

Do all intra-ventricular conduction defect ECG patterns respond equally to CRT?

Response to cardiac resynchronization therapy (CRT) is well-established in patients with typical left bundle branch block (LBBB) but modest or even negative in those with intraventricular conduction delay (IVCD). However, IVCD pattern is heterogeneous, and it is possible that QRS patterns may also respond to CRT. Consecutive baseline ECGs of 239 patients implanted between 2007 and 2010 with CRT were analyzed. ECGs were classified into the following three groups: (a) typical LBBB (TLBBB) according to accepted guidelines (n= 67); (b) IVCD with LBBB pattern criteria in V1, 1, and aVL but with QS or rS in V5-V6 which we defined as atypical LBBB (ALBBB) (n= 74); and (c) all other IVCD (OIVCD) patterns (n= 98). Endpoints were 2years mortality and echocardiographic response, defined as a decrease of ≥ 10% in indexed LVESV or an increase of ≥ 5% in left ventricular ejection fraction at 1year of follow-up. Baseline clinical characteristics were similar among all the three groups. Rates of echocardiographic response were lower among those with OIVCD compared to those with LBBB and ALBBB (50% vs. 75% and 72%, respectively, p= 0.01 for both comparisons). A multivariable model showed a lower likelihood of echocardiographic response in OIVCD [HR = 0.40; (0.16-0.98)] and a similar likelihood in ALBBBB [HR = 0.98; (0.40-2.40)] compared to TLBBB. Cumulative 2-year survival was 88% in ALBBB, 86% in TLBBB, and 76% in OIVCD (p value = 0.011). Patients with ALBBB may have a favorable echocardiographic response to CRT and display similar survival rates to typical LBBB. This subgroup of IVCD should be considered for CRT. Atypical left bundle branch morphology defined as QS or rS in lead V1, broad R waves in lead I, and aVL but with QS or rS in V5-V6 is associated with favorable echocardiographic response to CRT and displays similar survival rates to typical LBBB patients.

Unusual manifestation of left ventricular electrical conduction delay on the surface 12-lead electrocardiogram in a patient with prior myocardial infarction

We describe a 41-year-old man with a prior history of myocardial infarction, whose surface 12-lead electrocardiogram did not show typical left bundle-branch block pattern or wide QRS complex. However, electrophysiological study showed distinct left ventricular electrical conduction delays. The surface 12-lead electrocardiogram modified to the paper at 50 mm/s and double standard (20 mm equals 1 mV) revealed obvious notches of the terminal forces of the QRS in leads II, III, aVL, aVF, V3, V4, V5, and V6, these might be partially consistent with left ventricular electrical conduction delay in the scar lesion of the infero-posterior of the ventricle.

Intracardiac Delineation of Septal Conduction in Left Bundle-Branch Block Patterns.

Septal activation in patients with left bundle-branch block (LBBB) patterns has not been described previously. We performed detailed intracardiac mapping of left septal conduction to assess for the presence and level of complete conduction block (CCB) in the His-Purkinje system. Response to His bundle pacing was assessed in patients with and without CCB in the left bundle. Left septal mapping was performed with a linear multielectrode catheter in consecutive patients with LBBB pattern referred for device implantation (n=38) or substrate mapping (n=47). QRS width, His duration, His-ventricular (HV) intervals, and septal conduction patterns were analyzed. The site of CCB was localized to the level of the left-sided His fibers (left intrahisian) or left bundle branch. Patients with ventricular activation preceded by Purkinje potentials were categorized as having intact Purkinje activation. A total of 88 left septal conduction recordings were analyzed in 85 patients: 72 LBBB block pattern and 16 controls (narrow QRS, n=11; right bundle-branch block, n=5). Among patients with LBB block pattern, CCB within the proximal left conduction system was observed in 64% (n=46) and intact Purkinje activation in the remaining 36% (n=26). Intact Purkinje activation was observed in all controls. The site of block in patients with CCB was at the level of the left His bundle in 72% and in the proximal left bundle branch in 28%. His bundle pacing corrected wide QRS in 54% of all patients with LBBB pattern and 85% of those with CCB (94% left intrahisian, 62% proximal left bundle-branch). No patients with intact Purkinje activation demonstrated correction of QRS with His bundle pacing. CCB showed better predictive value (positive predictive value 85%, negative predictive value 100%, sensitivity 100%) than surface ECG criteria for correction with His bundle pacing. Heterogeneous septal conduction was observed in patients with surface LBBB pattern, ranging from no discrete block to CCB. When block was present, we observed pathology localized within the left-sided His fibers (left intrahisian block), which was most amenable to corrective His bundle pacing by recruitment of latent Purkinje fibers. ECG criteria for LBBB incompletely predicted CCB, and intracardiac data might be useful in refining patient selection for resynchronization therapy.

Electrophysiological Characteristics of Bundle Branch Reentry Ventricular Tachycardia in Patients Without Structural Heart Disease

The distinct electrophysiological features of bundle branch reentry ventricular tachycardia (VT) in patients without structural heart disease have not been systemically characterized. Nine patients (mean age, 29.6 years) with normal left ventricular function were enrolled. Bundle branch reentry VT with right and left bundle branch block (BBB) patterns was induced in 1 and 9 patients, respectively. The right bundle was attempted to record by a 6F decapolar or quadripolar catheter. Electroanatomic mapping of the left ventricle was performed in 6 patients. In all left BBB pattern VT, the mean VT cycle length was 329.3±89.1 ms, and the median HV interval during tachycardia was longer than that of baseline (78 [73-100] versus 71 [64.5-88] ms; P=0.11). The H-RB interval during VT was slightly shorter (P=0.14); however, the median RB-V interval was markedly longer than that during sinus rhythm (50 [29.5-83] versus 30 [8-51] ms; P=0.043]. In 6 patients with 3-dimensional mapping of the left ventricle, a slow anterograde or retrograde conduction over left HIS-Purkinje system with normal myocardial voltage was identified. In addition, Purkinje-related VTs (1.0±1.3 types) were also induced in 5 patients. Ablation was applied in distal left BB in patients with baseline left BBB and in one narrow QRS patient with sustained Purkinje-related VT, whereas right BB was targeted in other patients. During a mean follow-up of 31.4 months, frequent premature ventricular contractions occurred in one patient, and new VT developed in the other patient. Bundle branch reentry VT can occur in young patients with extensive conduction disturbances within HIS-Purkinje system. Ablation targeting at the distal left BB which bifurcates into left posterior and anterior fascicle can preserve the residual atrioventricular conduction, but intensive follow-up is needed.

Evaluation of the predictive value of Gensini score on determination of severity of coronary artery disease in cases with left bundle branch block

Abstract Left bundle branch block (LBBB) is one of the features which predicts severe organic heart disease. In this study, we aimed to examine the predictive role of Gensini score as marker of severity of coronary artery disease (CAD) in patients with LBBB and its relationship with other CAD risk factors and complications. We have included patients who referred to our center for selective coronary angiography with transient and or permanent LBBB on their surface electrocardiography (ECG). Cases with pacemaker rhythm and known non-CAD related causes of LBBB pattern on surface ECG were excluded from this study. Demographic variables and clinical features were studied. To determine severity of CAD, Gensini score was measured. The relationship between presence of CAD and deteriorated ejection fraction has been demonstrated by previous works, but we found no association between severity of CAD and degree of ejection fraction deterioration. This might imply to the role of non-CAD factors toward reduction of ejection fraction. In cases with hypertension in the setting of LBBB, higher Gensini scores were seen regardless of ventricular ejection fraction. Thus, earlier screening for possible CAD in cases with LBBB and hypertension seems rational. Keywords: Left bundle branch block Electrocardiography Severity of coronary artery disease Gensini score

An electrocardiographic diagnostic model for differentiating left from right ventricular outflow tract tachycardia origin.

Although several electrocardiographic (ECG) algorithms have been proposed for differentiating the origins of outflow tract ventricular arrhythmias, the most optimal one has not been agreed on. The purpose of this study was to establish an ECG diagnostic model based on the previous ECG algorithms. The following ECG diagnostic model, Y=-1.15×( TZ )-0.494×(V2S/V3R), was developed by standard 12-lead ECG algorithms in 488 patients with idiopathic premature ventricular contractions or ventricular tachycardia with a left bundle branch block pattern and inferior axis QRS morphology. Binary logistic regression analysis was performed to establish the ECG diagnostic model. The ECG diagnostic model consisted of two ECG algorithms-the transition zone (TZ) index and V2S/V3R index. The area under the curve by receiver operating characteristic curve analysis for the ECG diagnostic model was 0.88, with a cut-off value of ≥ -0.76 predicting a left ventricular outflow tract (LVOT) origin with a sensitivity of 82% and a specificity of 86%, which was higher than other ECG algorithms in this study. The predictive accuracy of the ECG diagnostic model was also the best among all ECG algorithms in patients with a lead V3 precordial transition. This model was tested prospectively in 207 patients with a sensitivity of 90%, a specificity of 87%, and Youden index of 0.77. A highly accurate ECG diagnostic model for correctly differentiating LVOT origin from right ventricular outflow tract origin was developed.

Left bundle branch block in Duchenne muscular dystrophy: Prevalence, genetic relationship and prognosis.

BackgroundDuchenne muscular dystrophy (DMD) is an inherited myogenic disorder due to mutations in the dystrophin gene on chromosome Xp21.1. We designed this study to determine the prevalence of left bundle branch block (LBBB), whether there is a relationship between LBBB and genetic pattern, and to assess predictive factors for acute cardiac events and mortality in adult DMD patients.MethodsWe reviewed the charts of DMD followed at the Home Mechanical Ventilation Unit of the Raymond Poincare University Hospital.ResultsA total of 121 patients, aged from 18 to 41 years have been included in our study. Median vital capacity (VC) was 12% [7; 19.5] of predicted. Almost all patients were on home mechanical ventilation (95%). LBBB was present in 15 patients (13%); among them, 10 disclosed exonic deletions. After a median follow up of 6 years, 21 patients (17%) experienced acute heart failure (AHF), 7 patients (6%) supraventricular arrhythmia, 3 patients (2.4%) ventricular tachycardia, 4 patients (3%) significant electrical disturbances. LBBB was significantly associated with cardiac events (OR = 12.7; 95%CI [3.78–42.7]; p <0.0001) and mortality (OR = 4.4; 95%CI [1.44–13.7]; p 0.009). Presence of residual dystrophin protein was not associated with significant less cardiac events. Age and LVEF were also predictive factors for cardiac events and mortality.ConclusionLBBB is relatively frequent in DMD and is a major predictive factor for cardiac events and mortality. Presence of residual dystrophin protein was not associated with a lower incidence of cardiac events.

Clinical Profile of the Patients with Newly Detected Left Bundle Branch Block in the Outpatient Department

Objective: The purpose of this study was to evaluate cardiac features associated with newly detected left bundle branch block (LBBB) in the outpatient department. Methods: A total of 57 patients with LBBB pattern were evaluated using electrocardiography (ECG). Patients were assessed based on their sex, age, detailed history, and cardiovascular symptoms. Cardiac investigations including ECG and echocardiography were performed. Results:The study included 30 (52.6%) males and 27 (47.5%) females, aged between 35 and 80 years. Dyspnoea (35.1%) and chest pain (22.8%) were the most common symptoms. 54.4% were hypertensive and 17.5% were diabetics. 28% had Left ventricular systolic dysfunction, and 24.5% had aortic valve disease. Left ventricular hypertrophy without any other structural heart disease was present in 28% of the patients. Only 24.5% patients presented with LBBB had a structurally normal heart in echocardiography. Myocardial performance index in echocardiography was abnormal in LBBB irrespective of the presence of structural heart disease. Conclusion: The prevalence of LBBB was found to increase with age and had slight male preponderance. Dyspnoea on effort was the most common presenting complaint, followed by chest pain and incidental detection of ECG abnormality. Most of the patients were hypertensive. Only 24.5% patients with LBBB had a structurally normal heart. MPI was abnormally high in the presence of LBBB despite having a normal left ventricular ejection fraction.

Electrocardiographic patterns in biventricular pacing delivered by second-generation cardiac resynchronization devices

BackgroundWith increasing use of cardiac resynchronization therapy (CRT), treating physicians should be familiar with different electrocardiographic (ECG) patterns of left ventricular (LV) lead and biventricular (BiV) pacing. However, there are a few publications on ECG patterns during BiV pacing. PurposeThis study was sought to determine different ECG patterns in patients with BiV pacing. MethodsTwelve-lead ECGs during BiV pacing (right ventricular leads at apex and LV leads in one of the lateral coronary veins) were analyzed in 181 consecutive patients (121 male; mean age, 62.0 ± 13.5 years) with advanced heart failure and baseline left bundle branch block pattern after at least 6-month of uncomplicated CRT. ResultsDuring BiV pacing, 65% of the patients showed a dominant R wave in V1. There was a right axis deviation in 57% in frontal plane. However, a left superior axis emerged in 34% and normal frontal plane axis in 9%. Sequential BiV pacing (73% vs. 58%, P = 0.04) and pacing from posterolateral coronary vein (80% vs. 60%, p = 0.045) were more likely to present with a dominant R wave in V1. In sequential pacing, AV interval was significantly longer in patients with negative complex in V1 than in those with positive complex (124 ± 21 vs. 116 ± 8.0, p = 0.005). A Q/q wave was detected in 85% of patients in lead I and 78% in lead aVL. ConclusionsBiV pacing from lateral coronary venous branches and right ventricular apex characteristically presented with dominant R wave in V1, Q/q wave in leads I and aVL, and right or left superior axis. However, a negative complex in V1, QRS axis in other quadrants, and lack of Q/q wave in leads I and aVL did not necessarily indicate a problem.

Managing chest pain in patients with concomitant left bundle-branch block.

Diagnosis and timely management of acute myocardial infarction (MI) relies heavily on the ST-segment elevation sum. Presence of concomitant left bundle-branch block (LBBB) in patients presenting with possible acute MI presents a diagnostic dilemma. The LBBB pattern distorts ST-segment changes, delaying or preventing accurate diagnosis. This article reviews the Sgarbossa criteria and ST/S ratio and presents a treatment algorithm that may help improve patient care and reduce morbidity and mortality.

Permanent His bundle pacing to replace biventricular pacing for cardiac resynchronization therapy

IntroductionCardiac resynchronization therapy (CRT) or biventricular pacing (BIVP) has become a common procedure for the treatment of ventricular dyssynchrony in patients with heart failure, particularly in those with bundle branch block patterns (QRS durations >150ms) on the electrocardiogram (ECG). However, a large group of non-responders are made up of patients with dyssynchrony and QRS duration below 130ms. Recent studies have introduced permanent His bundle pacing as another method for achieving normalization of the QRS duration even in a majority of patients with right or left bundle branch block pattern on the ECG. HypothesesWe hypothesize 1. Biventricular pacing, (BIVP) performed as the standard procedure for CRT is inherently abnormal, spatially, at the right and left ventricular apex, and temporally, in regard to the timing of normal activation of the interventricular conduction system. Corollary 1. Permanent, selective, His bundle pacing (PHBP) is the most physiological form of ventricular pacing which replicates the normal activation of the interventricular conduction system. Corollary 2. An appropriately powered, prospective, crossover trial comparing PHBP with BIVP will show that the former is associated with the same benefits in patients with heart failure and QRS durations >130ms and would improve, rather than worsen, outcomes in heart failure patients with QRS duration <130ms. We present experimental and clinical evidence in support of these hypotheses.

Atriofascicular Mahaim with Ebstein anomaly: A case report

We report a case of a 7-year-old girl with atriofascicular Mahaim (AFM) pathway concomitant with Ebstein's anomaly. The QRS wave showed left bundle branch block pattern on electrocardiogram. Holter electrocardiogram showed prolongation of the PR interval and QRS morphological change during sinus tachycardia. An electrophysiological study demonstrated that the distal His potential appeared earlier than the proximal His potential, which suggested retrograde His conduction toward the atrioventricular node. Conduction from the Mahaim fiber to the His bundle was faster than that from the atrioventricular node towards the His bundle. The findings of this important case allowed a differential diagnosis between AFM and Wolff-Parkinson-White (WPW) syndrome.