Radiofrequency catheter ablation of upper septal idiopathic left ventricular tachycardia exhibiting left bundle branch block morphology

Idiopathic left ventricular (LV) tachycardia usually exhibits right bundle branch block morphology. There are only a few sporadic cases that exhibit left bundle branch block (LBBB) morphology. We report a patient whose QRS complex during ventricular tachycardia (VT) was relatively narrow (100 msec) and exhibited LBBB (precordial R wave transition between V3 and V4) and a normal frontal plane axis. This VT was ablated successfully by radiofrequency current applied to the LV upper septum, where the earliest endocardial activation was recorded.     

Limitations of the electrocardiographic diagnosis of left ventricular hypertrophy: the influence of left anterior hemiblock and right bundle branch block.

We analysed the performance of the electrocardiogram in diagnosing left ventricular hypertrophy in 70 patients with isolated left anterior hemiblock and in 75 patients with right bundle branch block, either isolated (44 cases) or associated (31 cases) with left anterior hemiblock. Left ventricular hypertrophy defined as an echocardiographically determined left ventricular mass greater than 261 g in men and 172 g in women or left ventricular mass index greater than 125 g/m2 in men and 112 g/m2 in women was present in 48 subjects (57%) with isolated left anterior hemiblock and 33 subjects (44%) with right bundle branch block. In patients with isolated left anterior hemiblock the best results were obtained using the SV1 or SV2 + (RV6 + SV6) greater than 25 mm with 74% in sensitivity and 67% in specificity; the criterion SIII + (R + S) maximal in a precordial lead greater than or equal to 30 mm showed a sensitivity of 74% but a specificity of 47%. In the whole group of patients with right bundle branch block none of the criteria nor combination of criteria achieved an acceptable performance (sensitivities ranged from 17% to 41% and specificities ranged from 54% to 85%). When these patients were divided according to the presence or absence of concomitant left anterior hemiblock the electrocardiographic indexes mostly showed, in comparison to whole group, higher values in sensitivity and lower values in specificity in right bundle branch block plus left anterior hemiblock and an opposite behaviour in isolated right bundle branch block.(ABSTRACT TRUNCATED AT 250 WORDS)     

A case of alternating bundle branch block in combination with intra-Hisian block

We describe a 66-year-old woman who had an alternating bundle branch block consisting of coexisting occurrence of right bundle branch block (RBBB) and left bundle branch block (LBBB) combined with Mobitz type II atrioventricular block (AVB). A prolonged PQ interval was associated with the RBBB pattern whereas it was not apparent in the LBBB pattern. Electrophysiologic study revealed that the LBBB pattern was combined with a double His bundle potential. On the other hand, the RBBB pattern was combined with a markedly prolonged HV interval with a low voltage monophasic His bundle potential, which we speculated was the former part of the split His bundle potential seen during the LBBB pattern. A combination of the longitudinal dissociation in the His bundle and the gap phenomenon at the intra-Hisian block portion may account for this observation.     

Effect of preexisting bundle branch block on the electrocardiographic diagnosis of ventricular tachycardia

The electrocardiograms (ECGs) of 80 ventricular tachycardias (VTs) occurring in 52 patients with a normal baseline QRS duration (group 1) were compared with 26 VTs in 18 patients with preexisting bundle branch block (group 2). The effects of bundle branch block on the sensitivity of previously defined electrocardiographic criteria for differentiating VT from supraventricular tachycardia with aberration were under investigation. Specificity was examined by comparing VT to the baseline ECG in group 2 patients. The VTs in groups 1 and 2 were comparable with respect to rate, bundle branch pattern, R-wave pattern in V1 with right bundle, frequency of an R/S ratio less than 1 in V6 with right bundle, Q-wave frequency in V6 with left bundle and quadrant of the frontal plane axis. Precordial QRS concordance was more frequent (35 vs 15%, p = 0.045) and a greater than 30 ms R wave in V1 or V2 with left bundle pattern was less frequent (18 vs 63%, p = 0.015) in group 2 vs group 1 arrhythmias. Right bundle pattern VT usually had a monophasic R wave in V1 (69%), whereas preexisting right bundle usually had a biphasic R wave in V1 (82%, p = 0.001). The quadrant of the frontal plane axis was significantly different between the VT ECGs and the ECGs with preexisting bundle branch block (p = 0.029) with a right superior quadrant axis only seen in VT (19%). A greater than 30 ms R wave in V1 or V2 with left bundle was also only seen in VT (52 vs 0%, p = 0.052).(ABSTRACT TRUNCATED AT 250 WORDS)     

The Surface Electrocardiogram Predicts Risk of Heart Block During Right Heart Catheterization in Patients With Preexisting Left Bundle Branch Block: Implications for the Definition of Complete Left Bundle Branch Block

LBBB and Heart Block . Background: Patients with left bundle branch block (LBBB) undergoing right heart catheterization can develop complete heart block (CHB) or right bundle branch block (RBBB) in response to right bundle branch (RBB) trauma. We hypothesized that LBBB patients with an initial r wave (≥1 mm) in lead V1 have intact left to right ventricular septal (VS) activation suggesting persistent conduction over the left bundle branch. Trauma to the RBB should result in RBBB pattern rather than CHB in such patients. Methods: Between January 2002 and February 2007, we prospectively evaluated 27 consecutive patients with LBBB developing either CHB or RBBB during right heart catheterization. The prevalence of an r wave ≥1 mm in lead V1 was determined using 118 serial LBBB electrocardiographs (ECGs) from our hospital database. Results: Catheter trauma to the RBB resulted in CHB in 18 patients and RBBB in 9 patients. All 6 patients with ≥1 mm r wave in V1 developed RBBB. Among these 6 patients q wave in lead I, V5, or V6 were present in 3. Four patients (3 in CHB group and 1 in RBBB group) developed spontaneous CHB during a median follow‐up of 61 months. V1 q wave ≥1 mm was present in 28% of hospitalized complete LBBB patients. Conclusions: An initial r wave of ≥1 mm in lead V1 suggests intact left to right VS activation and identifies LBBB patients at low risk of CHB during right heart catheterization. These preliminary findings indicate that an initial r wave of ≥1 mm in lead V1, present in approximately 28% of ECGs with classically defined LBBB, may constitute a new exclusion criterion when defining complete LBBB. (J Cardiovasc Electrophysiol, Vol. pp. 781‐785, July 2010)     

Incessant slow bundle branch reentrant ventricular tachycardia in a young patient with left ventricular noncompaction

A 15-year-old girl was admitted to the cardiology outpatient clinic due to mild palpitations and documented incessant slow ventricular tachycardia (VT) with left bundle branch block (LBBB) pattern. The baseline electrocardiogram revealed first-degree atrioventricular block and intraventricular conduction defect. Transthoracic echocardiography showed prominent trabeculae and intertrabecular recesses suggesting left ventricular noncompaction (LVNC), which was confirmed by cardiac magnetic resonance imaging. During electrophysiological study, a sustained bundle branch reentrant VT with LBBB pattern and cycle length of 480 ms, similar to the clinical tachycardia, was easily and reproducibly inducible. As there was considerable risk of need for chronic ventricular pacing following right bundle ablation, no ablation was attempted and a cardioverter-defibrillator was implanted. To the best of our knowledge, no case reports of BBR-VT as the first manifestation of LVNC have been published. Furthermore, this is an extremely rare presentation of BBR-VT, which is usually a highly malignant arrhythmia.     

Usefulness of left atrial abnormality for predicting left ventricular hypertrophy in the presence of left bundle branch block

The objective of this study was to identify left atrial (LA) abnormality on the electrocardiogram and other related variables as predictors of left ventricular (LV) hypertrophy in the presence of left bundle branch block (LBBB). In the presence of complete LBBB, the diagnosis of electrocardiographic abnormalities is problematic and that of LV hypertrophy remains difficult. The usual electrocardiographic criteria applied for the diagnosis of LV hypertrophy may not be reliable in the presence of LBBB. Therefore, noninvasive criteria will help physicians diagnose LV hypertrophy with electrocardiography. LA abnormality on the electrocardiogram was assessed by 2 independent observers as predictor of LV hypertrophy in the presence of LBBB in 120 patients, and data were compared with those of 100 patients without LA abnormality. LV mass was calculated from echocardiographic data. Besides LA abnormality, the other variables studied for prediction of LV hypertrophy were gender, age, body surface area, body mass index, frontal axis, and QrS duration. Of the 6 criteria analyzed, the P terminal force was found to be the most common and consistent criterion to detect LA abnormality. LV hypertrophy was confirmed by echocardiographic determination of LV mass in both groups. Observers reliably differentiated between the hypertrophied and normal-sized left ventricle in the presence of LBBB by correlating LA abnormality with LV mass determined by echocardiography. Observer 1 detected LA abnormality in 89% and observer 2 in 84% of patients. False-positive results were present in 11% and 16%. The observer's recognition of LA abnormality in the present study was 91%. The 2 observers showed a sensitivity of 81% and 79% and a specificity of 91% and 88%, respectively, when diagnosis of LV hypertrophy was determined. LV mass increased significantly and was diagnostic of LV hypertrophy in 92% of patients with LA abnormality. In the remaining 11 patients (8%), the LA abnormality was of marginal abnormal magnitude. Each 0.01-mV/s increase in LA abnormality gave an increase of 30 g of LV mass. LV mass was increased in 86% of patients when corrected by body surface area. LV hypertrophy in the presence of LBBB on electrocardiography was found in only 13 patients (10%) when the 6 frequently used conventional criteria for diagnosis of LV hypertrophy by electrocardiography were used. Regression analysis revealed LA abnormality to be a strong independent predictor of increased LV mass. Multivariate analysis also revealed age, body mass index, body surface area, frontal axis, and QrS duration to be significant predictors of LV mass. This noninvasive study correlates LA abnormality by electrocardiogram and LV hypertrophy with echocardiography to conclude that LA abnormality was significantly diagnostic of LV hypertrophy in the presence of LBBB. Age, body mass index, body surface area, frontal axis, and QrS duration were also significant predictors of LV mass.     

The role of left ventricular conduction in the electrogenesis of left ventricular hypertrophy. An electrophysiologic study in man.

Various electrocardiographic and vectorcardiographic (ECG-VCG) patterns of ventricular conduction disturbances are inducible by premature right atrial stimulation (PRAS). These patterns are a consequence of different degrees of refractoriness in the specialized ventricular conduction system. We observed that the intermediate phase of left bundle branch block (LBBB) induced by PRAS in 20 subjects with normal basal QRS (complexes) were similar to those of left ventricular hypertrophy (LVH). In 18 patients with basal ECG-VCG signs of LVH, right bundle branch block (RBBB) induced by PRAS produced a progressive disappearance of these signs and the "normalization" of the tracings. The initial maximum QRS vector decreased, disappeared or remained absent in the patients with LBBB induced by PRAS, and appeared (when absent in the basal VCG) and remained unchanged (when present) in patients with RBBB induced by PRAS. In this paper we discuss the electrogenetic implications of these data. The ECG-VCG sings of LVH are probably dependent on a slowed conduction in the left bundle branch system, while anatomical hypertrophy per se probably plays a less important role.     

Diagnostic accuracy of computer-assisted electrocardiography in the diagnosis of left ventricular hypertrophy in left bundle branch block

Introduction and objectives

Left ventricular hypertrophy has important prognostic implications. Although electrocardiography is the technique most often recommended in the diagnosis of hypertrophy, its diagnostic accuracy is hampered in the presence of a left bundle branch block.

Methods

In 1875 consecutive patients (56±16 years) undergoing studies to rule out heart disease and/or hypertension, 2-dimensional echocardiography and electrocardiography were performed simultaneously in an outpatient clinic. Digitized electrocardiograms were interpreted using an online computer-assisted platform (ELECTROPRES). Sensitivity, specificity, likelihood ratios, and predictive values of standard electrocardiographic criteria and of some diagnostic algorithms for left ventricular hypertrophy were determined and compared with the findings in patients with neither left bundle branch block nor myocardial infarction.

Results

Left bundle branch block was present in 233 (12%) patients. Left ventricular hypertrophy was detected more frequently in patients with left bundle branch block (60% vs 31%). In patients with left bundle branch block, sensitivities were low but similar to those observed in patients without it, and ranged from 6.4% to 70.9%, whereas specificities were high, ranging from 57.6% to 100%. Positive likelihood ratios ranged from 1.33 to 4.94, and negative likelihood ratios from 0.50 to 0.98. Diagnostic algorithms, voltage-duration products, and certain compound criteria had the best sensitivities.

Conclusions

Left ventricular hypertrophy can be diagnosed in the presence of left bundle branch block with an accuracy at least similar to that observed in patients without this conduction defect. Computer-assisted interpretation of the electrocardiogram may be useful in the diagnosis of left ventricular hypertrophy as it enables the implementation of more accurate algorithms.Full English text available from:www.revespcardiol.org     

Electrophysiologic characteristics of ventricular extrastimulation-induced dissipation of functional bundle branch block associated with supraventricular tachycardia

INTRODUCTION: Linking-related anterograde functional bundle branch block during supraventricular tachycardia (SVT) is due to repetitive concealed retrograde conduction of impulses from the contralateral bundle branch and can be eliminated by a critically timed premature ventricular beat (PVB). We assessed the electrophysiologic characteristics of PVB-induced dissipation of functional bundle branch block during SVT. METHODS AND RESULTS: During SVT with functional bundle branch block, PVB was delivered from the right ventricular apex, scanning the tachycardia cycle length (CL) with 10-msec decrements in the coupling interval in 14 patients (3 AV nodal reentrant tachycardia and 11 orthodromic AV reciprocating tachycardia). Dissipation was achieved in group 1: functional right bundle branch block (RBBB) in 4, functional left bundle branch block (LBBB) in 4, and both functional RBBB and LBBB in 1 with a dissipation zone occupying 4% to 13% (mean 8.5%) of the tachycardia CL. The outer limits were 22+/-16 msec and 68+/-14 msec < tachycardia CL; the inner limits were 56+/-18 msec and 90+/-24 msec < tachycardia CL for RBBB and LBBB, respectively (both P < 0.05). Dissipation could not be achieved in group 2 (4 RBBB and 1 LBBB) due to CL-dependent bundle branch block and/or local ventricular refractoriness. CONCLUSION: During SVT, functional bundle branch block due to "linking" often can be dissipated by timely PVB delivered from the right ventricular apex within a narrow zone of the tachycardia CL. Our findings suggest that the dissipation zone is affected by the pattern of functional bundle branch block relative to the site of PVB delivery.     

Improvement of left ventricular mechanical dyssynchrony associated with restoration of left ventricular function in a patient with fulminant myocarditis and complete left bundle branch block

A 52-year-old woman with fulminant myocarditis had completed left bundle branch block (LBBB) and severely impaired left ventricular (LV) function. Marked mechanical dyssynchrony with septal-to-posterior delay of 389 ms was observed by echocardiographic speckle tracking radial strain imaging on admission, which was dramatically improved to 106 ms after total recovery from acute myocarditis with restoration of LV ejection fraction whereas her electrocardiogram still showed complete LBBB.     

Left Bundle Branch Block,an Old–New Entity

Left bundle branch block (LBBB) is generally associated with a poorer prognosis in comparison to normal intraventricular conduction, but also in comparison to right bundle branch block which is generally considered to be benign in the absence of an underlying cardiac disorder like congenital heart disease. LBBB may be the first manifestation of a more diffuse myocardial disease. The typical surface ECG feature of LBBB is a prolongation of QRS above 0.11 s in combination with a delay of the intrinsic deflection in leads V5 and V6 of more than 60 ms and no septal q waves in leads I, V5, and V6 due to the abnormal septal activation from right to left. LBBB may induce abnormalities in left ventricular performance due to abnormal asynchronous contraction patterns which can be compensated by biventricular pacing (resynchronization therapy). Asynchronous electrical activation of the ventricles causes regional differences in workload which may lead to asymmetric hypertrophy and left ventricular dilatation, especially due to increased wall mass in late-activated regions, which may aggravate preexisting left ventricular pumping performance or even induce it. Of special interest are patients with LBBB and normal left ventricular dimensions and normal ejection fraction at rest but who may present with an abnormal increase in pulmonary artery pressure during exercise, production of lactate during high-rate pacing, signs of ischemia on myocardial scintigrams (but no coronary artery narrowing), and abnormal ultrastructural findings on myocardial biopsy. For this entity, the term latent cardiomyopathy had been suggested previously.     

Defining left bundle branch block in the era of cardiac resynchronization therapy

Cardiac resynchronization therapy (CRT) has emerged as an attractive intervention to improve left ventricular mechanical function by changing the sequence of electrical activation. Unfortunately, many patients receiving CRT do not benefit but are subjected to device complications and costs. Thus, there is a need for better selection criteria. Current criteria for CRT eligibility include a QRS duration ≥ 120 ms. However, QRS morphology is not considered, although it can indicate the cause of delayed conduction. Recent studies have suggested that only patients with left bundle branch block (LBBB) benefit from CRT, and not patients with right bundle branch block or nonspecific intraventricular conduction delay. The authors review the pathophysiologic and clinical evidence supporting why only patients with complete LBBB benefit from CRT. Furthermore, they review how the threshold of 120 ms to define LBBB was derived subjectively at a time when criteria for LBBB and right bundle branch block were mistakenly reversed. Three key studies over the past 65 years have suggested that 1/3 of patients diagnosed with LBBB by conventional electrocardiographic criteria may not have true complete LBBB, but likely have a combination of left ventricular hypertrophy and left anterior fascicular block. On the basis of additional insights from computer simulations, the investigators propose stricter criteria for complete LBBB that include a QRS duration ≥ 140 ms for men and ≥ 130 ms for women, along with mid-QRS notching or slurring in ≥ 2 contiguous leads. Further studies are needed to reinvestigate the electrocardiographic criteria for complete LBBB and the implications of these criteria for selecting patients for CRT.     

伴右心室出口的左心室起源缺血性室性心动过速的标测和消融

目的折返性的缺血性室性心动过速（VT）绝大多数发生于左心室并表现为右束支阻滞（RBBB）图形。本文报道1组VT折返环位于左心室但出口在右心室且表现为左束支阻滞（LBBB）的病例。方法32例因陈旧性心肌梗死伴VT而接受电生理检查和射频消融的患者,其中4例临床有LBBB形态的VT。使用非接触等电位和虚拟单极标测判断VT起源,结合舒张中期电位（MDP）和拖带标测确定折返关键通路和消融靶点。用盐水冲洗电极导管在折返环的关键峡部行线性消融。结果全部32例患者中,4例临床有LBBB型VT者均成功被诱发,其中1例有两种LBBB型VT,1例同时有RBBB型VT但周长与LBBB型相同;另有1例共有6种形态的VT,包括RBBB和LBBB型。在右心室内的非接触式等电位标测可迅速确定VT在右心室的传出部位,该处的虚拟单极标测显示rS型提示左心室起源。3例在左心室成功拖带并消融成功,靶点均紧邻左心室间隔,其中1例位于下壁,1例在前壁,1例两种LBBB型VT分别在前壁和下壁间隔旁消融成功。随访1～4．2年,未服抗心律失常药无VT发作。而1例诱发出6种单形（包括RBBB和LBBB型）VT患者因巨大室壁瘤及心功能障碍不能耐受而中途放弃消融。结论紧邻室间隔的前壁和下壁心肌梗死后的左心室起源VT可能因在右心室有出口而表现为LBBB型,需要在标测和消融时予以注意。     

Recovery of complete left bundle branch block following heart failure improvement by left bundle branch pacing in a patient

A 57‐year‐old male presented with symptomatic systolic heart failure and complete left bundle branch block (LBBB). Left bundle branch pacing corrected LBBB at a low capture threshold (0.5V @0.4ms) with right bundle branch conduction delay and paced QRS morphology changed to near‐normal by adjusting AV delay with diminished RBBD. At 1‐year follow‐up, the patient had a significant improvement in heart failure and LBBB automatically resolved with a rate‐dependent pattern. LBBP may be an alternative to conventional cardiac resynchronization therapy with the likelihood of recovery of LBBB. More research is needed to evaluate the potential use of this pacing strategy in patients with LBBB and heart failure.     

Isolated and complicated left anterior fascicular block: a review of suggested electrocardiographic criteria

The electrocardiographic criteria for isolated left anterior fascicular block are reviewed and illustrated. Left anterior fascicular block decreases the voltage in the chest leads and increases the voltage in the limb leads. The usual voltage criteria of left ventricular hypertrophy must be modified appropriately. Changes in repolarization include a decrease in the T wave of leads I and AVL and an increase in leads II, III, AVF, V5 and V6. Small Q waves in V2 may simulate an anteroseptal myocardial infarction. Three criteria for the possible diagnosis of superimposed inferior myocardial infarction have been suggested. Both inferior and anterior myocardial infarctions may be masked by R waves replacing Q waves. In the presence of a recent anterior infarction, right bundle branch block may also be masked. Thus, left anterior fascicular block may mask or mimic infarction and left ventricular hypertrophy and mask right bundle branch block in the setting of an acute anterior myocardial infarction.     

Differentiation between left bundle branch block and left ventricular hypertrophy: Implications for cardiac resynchronization therapy

Recent clinical trials have demonstrated that cardiac resynchronization therapy (CRT) reduces heart failure hospitalizations and mortality in patients with complete left bundle branch block (LBBB), but potentially not those with right bundle branch block or nonspecific LV conduction delay, such as that due to LV hypertrophy (LVH). Furthermore, endocardial mapping and simulation studies have suggested that one-third of patients diagnosed with LBBB by conventional electrocardiographic criteria are misdiagnosed, and these patients likely have a combination of LVH, LV chamber dilatation and delayed initiation of LV activation (incomplete LBBB). Increase in LV size due to hypertrophy/dilatation and slowed intramyocardial conduction velocity prolong QRS duration in patients with LVH, which can frequently go above the QRS duration threshold of 120 ms conventionally used to diagnose LBBB. New strict criteria for diagnosing complete LBBB have been proposed that utilize longer QRS duration thresholds (130 ms in women and 140 ms in men) and require the presence of mid-QRS notching/slurring in at least 2 of the leads I, aVL, V1, V2, V5 or V6. The emergence of CRT has led to an increased need to differentiate complete LBBB from LVH and other types of intraventricular conduction delay, which should be further studied.     

Comment on "Defining left bundle branch block in the era of cardiac resynchronization therapy"

Cardiac resynchronization therapy (CRT) has emerged as an attractive intervention to improve left ventricular mechanical function by changing the sequence of electrical activation. Unfortunately, many patients receiving CRT do not benefit but are subjected to device complications and costs. Thus, there is a need for better selection criteria. Current criteria for CRT eligibility include a QRS duration >120 ms. However, QRS morphology is not considered, although it can indicate the cause of delayed conduction. Recent studies have suggested that only patients with left bundle branch block (LBBB) benefit from CRT, and not patients with right bundle branch block or nonspecific intraventricular conduction delay. The authors review the pathophysiologic and clinical evidence supporting why only patients with complete LBBB benefit from CRT. Furthermore, they review how the threshold of 120 ms to define LBBB was derived subjectively at a time when criteria for LBBB and right bundle branch block were mistakenly reversed. Three key studies over the past 65 years have suggested that 1/3 of patients diagnosed with LBBB by conventional electrocardiographic criteria may not have true complete LBBB, but likely have a combination of left ventricular hypertrophy and left anterior fascicular block. On the basis of additional insights from computer simulations, the investigators propose stricter criteria for complete LBBB that include a QRS duration >140 ms for men and >130 ms for women, along with mid-QRS notching or slurring in >2 contiguous leads. Further studies are needed to reinvestigate the electrocardiographic criteria for complete LBBB and the implications of these criteria for selecting patients for CRT.     

超声评价LBBB对左室整体和局部活动的影响

目的　超声评价LBBB患者左室整体和局部活动。方法　超声测量 15例LBBB患者 (LBBB组 )和 15例正常人 (control组 )各瓣环 ,获得各时相的持续时间 (ICT、ET、IRT、DET) ,评价左室整体和局部Z指数 [(ET DFT) /R R],并测量等容收缩期波峰的加速时间 (IVA)、射血期波峰的加整时间 (Sac)、E波的减速时间 (Edc)。结果　LBBB患者左室整体和局部Z指数明显减低 ,各壁ICT明显延长 ;左室室间隔、下壁的IRT和IVA延长 ,DFT和Edc缩短 ,ICT/ET增加。结论　LBBB时室壁激动的异常 ,影响左室整体和局部舒缩活动