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Left bundle branch block (LBBB) and right bundle branch block (RBBB) are classic manifestations of bundle branch conduction disorders. However, a third form that is uncommon and underrecognized may exist that has features and pathophysiology of both: bilateral bundle branch block (BBBB). This unusual form of bundle branch block exhibits an RBBB pattern in lead V1 (terminal R wave) and an LBBB pattern in leads I and aVL (absence of S wave). This unique conduction disorder may confer an increased risk of adverse cardiovascular events. BBBB patients may be a subset of patients that respond well to cardiac resynchronization therapy.

The 12-lead electrocardiogram (ECG) of a 79-year-old male patient with recurrent pre-syncope showed irregular sinus rhythm with constant PR interval and left bundle branch block (LBBB) with intermittently blocked P waves. The beat following the blocked P wave had a narrower QRS with a shorter PR interval. The phenomenon of bilateral bundle branch block explains the sudden improvement in the atrioventricular conduction.

International audience; Refers To Gianni Pastore, Massimiliano Maines, Lina Marcantoni, Francesco Zanon, Franco Noventa, Giorgio Corbucci, Enrico Baracca, Silvio Aggio, Claudio Picariello, Daniela Lanza, Gianluca Rigatelli, Mauro Carraro, Loris Roncon, S. Serge Barold ECG parameters predict left ventricular conduction delay in patients with left ventricular dysfunction Heart Rhythm, Volume 13, Issue 12, December 2016, Pages 2289-2296

A 57 year-old man treated with amitriptyline was admitted because of several episodes of syncope. In ECG, the incomplete left bundle branch block was masked by the complete right bundle branch block and left anterior fascicular block.

Introduction: The mechanism of wide QRS complex tachycardias during dofetilide infusion was studied in a patient with atrial fibrillation.Methods and Results: Endocardial recordings from the intraventricular conduction system showed that dofetilide caused ''classic'' aberrant conduction (Ashman phenomenon, typical QRS morphology) at high prematurity ratios (preceding interval = 1.78 X coupling interval -290), thus mimicking ventricular ectopy. In addition, there was frequent sequential bilateral bundle branch block, caused by a significant difference in preceding bundle-to-bundle intervals (mean difference +/- 1 SD: 74 +/- 26 msec).Conclusion: The present findings may prove helpful in the clinical assessment of wide QRS complex rhythms after dofetilide and possibly other ''Pure'' Class III antiarrhythmics.

A proper characterization of frequency-dependent bundle branch blocks can provide useful prognostic information in some clinical situations. Often, this physiological event may be due to an extensive damage of infrahisian system, which poses a high risk of developing advanced atrioventricular block requiring pacemaker implantation. We describe the case of a 62 year-old man with chronic ischemic heart disease who exhibited alternating tachycardia-dependent bundle branch block during stress test. We discuss the main prognostic implications of this unusual event in the context of systolic dysfunction.Una caracterización correcta de los bloqueos de rama dependientes de frecuencia, puede proporcionar información relevante en ciertas situaciones clínicas. A menudo, este evento fisiológico puede evidenciar la presencia de un daño extenso del sistema de conducción infrahisiano con riesgo elevado de bloqueo aurículo-ventricular avanzado y necesidad de implante de marcapasos. Describimos el caso de un hombre de 62 años con cardiopatía isquémica crónica, que exhibió un bloqueo de rama bilateral alternante taquicardia-dependiente durante el esfuerzo ergométrico, discutiendo las principales implicancias pronósticas de este evento inusual en el contexto de la disfunción sistólica.

Catheter-induced arrhythmia is a well-recognized complication encountered during insertion of conventional of flow-directed balloon-tipped catheters. We describe a case of iatrogenically induced asystole due to the production of bilateral bundle branch block and the absence of an escape rhythm in a patient with a preexisting LBBB

A 29-year-old female with Uhl's anomaly developed complete atrioventricular (A-V) block. His bundle studies revealed block distal to the His bundle recording site with narrow QRS complexes. Right ventricular capture could not be obtained and despite successful left ventricular epicardial pacing, the patient died. Autopsy revealed absence of myocardium in most areas of the right ventricle and the right side of the ventricular septum with a normal tricuspid valve. Conduction system examination revelaed total destruction of both bundle branches. This is the first case where bilateral bundle branch block is shown to be present in Uhl's anomaly. Narrow QRS complexes probably reflected the absence of right ventricular forces.

Vectorcardiogram (VCG) recorded by both the Frank and Kimura systems were examined in 45 patients with complete right bundle branch block (RBBB) and left axis deviation (LAD) to investigate the relationship seen on electrocardiogram (ECG) between RBBB with LAD and bilateral bundle. The sample included: 13 cases of type SI, SII, SIII, SaVF; 21 cases of type SI, SII, SIII, aVF; and 11 cases of types SI, SII, SIII. VCG recorded by the Frank system were classified into seven types according to the QRS loop pattern on the frontal plane and into three types according to the horizontal plane. The main findings were: (a) In the Frank system the QRS loop in the frontal plane showed a variety of patterns in RBBB with LAD. (b) On VCG of complete RBBB judged complicated by a left anterior hemiblock by the Frank system, the main portion of the QRS loop extended to the left superior or merely to the left in the frontal plane. The direction of rotation and position on the horizontal plane were not consistent. (c) The results of this study suggest the usefulness of the Kimura system as an auxiliary diagnostic technique.

The localization of the conduction defect in so-called complete A-V block can be established by electrocardiography only indirectly and unreliably. In principle the region of the atrio-ventricular junction, i.e. the A-V node and the bundle of His, may be involved just as well as the two branches. Analysis of the configuration of the QRS complex in the electrocardiogram is unreliable, particularly in cases with bundle branch block, because any pattern can arise from the appropriate site of a tertiary focus of stimulation in one of the two ventricles. Recording His bundle potentials (His bundle electrogram) enables differentiation. In eleven personal observations and 151 cases collected from the literature of complete A-V block the analysis with this method showed that the so-called A-V block in the majority of cases (63%) is actually due to bilateral bundle branch block. In the other 37% an A-V junctional block was present. This type of block could be differentiated by means of His bundle electrograms into an A-V nodal block and His bundle block.

This report describes the clinical and electrocardiographic features in 30 cases of complete right bundle branch block associated with a block of the anterior fascicle of the left bundle branch, 7 of which also featured a block of the posterior fascicle of the left bundle branch (trifascicular block). The majority of the patients suffered from coronary atherosclerotic heart disease and/or hypertensive heart disease. Complete right bundle branch block associated with fascicular block of the left bundle branch constitutes a special electrocardiographic pattern. The prognosis of the patients presenting this pattern is poor, since it may develop into trifascicular block, i.e., complete atrioventricular block, often necessitating the implantation of artificial pacemakers.

The evolution of bilateral bundle branch block (BBB) was studied in ten anesthetized dogs by recording electrical activity from the bundle of His (Hb), right (Rb) and left bundles (Lb) for precise localization and characterization of the conduction disorder. Records were obtained before and at intervals up to 8 hours after ligation of the anterior septal artery. Forty to 140 min after ligation conduction was impaired in either the Rb or Lb showing complete BBB both at rapid heart rates (tachycardia-dependent) and slow rates (bradycardia-dependent) with normal QRS or incomplete BBB at control rates. Later complete BBB became constant at all heart rates. When both bundles were significantly involved, various combinations of intraventricular and atrioventricular conduction disorders occurred. Unequal delay in both bundles (unequal 1° bilateral BBB) gave rise to prolonged H-V interval and a QRS pattern of incomplete or complete bundle branch block corresponding to the branch in which the conduction delay was greater. Equal delay in both bundles gave rise to a narrow QRS with prolonged H-V interval. Second degree block in one bundle and complete (3°) block in the other manifested as 2:1, Mobitz type II, or Wenckebach A-V conduction disturbance. Unequal and asynchronous 2° bilateral BBB gave rise to complex patterns of alternating BBB associated with alteration in the H-V interval of 25-35 msec. In two experiments showing alternating BBB, longitudinal dissociation and asynchronous conduction in the distal Hb was suggested.

A simple quantitative diagram for analysis of electrocardiographic tracings suspected of bilateral bundle branch block is presented. It is particularly useful in cases of unequal asynchronous block of the two bundle branches. Four cases in which the diagram was of great help are presented. It is believed that the more widespread use of this diagram will facilitate teaching of the subject of bilateral bundle branch block and unearth many new cases. It is suggested that the diagram be used in cases showing changing QRS complexes, changing P–R intervals and some degree of atrioventricular block or a combination of at least two of these features.

Two cases of intermittent bundle-branch block in which Wenckebach periods could be directly visualized are reported. The conduction ratios were either 3:2 or 4:3, as are commonly seen in cases of the Wenckebach phenomenon of atrioventricular (A-V) conduction. Other groups of beats apparently showing 3:1 and 4:1 bundle-branch block were interpreted as indicating incompletely concealed Wenckebach periods in the bundle branches, with actual conduction ratios of 3:2 and 4:3, respectively. Three prerequisites are necessary for the occurrence of either direct or incompletely concealed Wenckebach periods in the bundle branches: (1) The opening beat should be normally conducted (in the affected bundle branch); (2) the second beat should be conducted with a delay of no more than 0.04 to 0.06 sec; (3) the damaged bundle branch should not be activated retrogradely in the closure beat. Wenckebach periods in the bundle branches may be completely concealed if the conduction delay lasts more than 0.04 to 0.06 sec in the opening beat. In cases of bilateral bundle-branch block, Wenckebach periods in the bundle branches may be indirectly visualized through changes in the A-V conduction.

Indirect graphic studies were performed in twenty-two patients with bilateral bundle branch block. Various estimations of left ventricular contractility derived from the apex cardiogram, phonocardiogram and carotid pulse tracings reflected the clinical state of the patient and were apparently uninfluenced by the presence of bilateral bundle branch block. On the other hand, the morphology of the apex cardiogram was quite remarkable in that a discrete early or late systolic bulge occurred in 20 of the 22 patients studied. It is suggested that block of the anterior division of the left bundle branch in the presence of right bundle branch block alters left ventricular activation in such a manner as to promote the development of left ventricular dyskinesis. If this is true, it would broaden the concept of ventricular dyskinesis to include alterations in the time course of left ventricular activation in addition to localized myocardial ischemia.

Thirty patients with electrocardiographic evidence of bilateral bundle branch block (BBBB) underwent 36 surgical procedures. Despite an 83 percent incidence of significant cardiac disease, the overall mortality was 10 percent. In no case was death attributable to complete heart block, though one patient was found at postmortem to have suffered acute myocardial infarction. Patients with previous syncopal episodes showed no increased incidence of arrhythmias and no patient had a documented Stokes-Adams attack. It would appear that the routine use of temporary cardiac pacemakers is not justified in the preoperative patient with presumed BBBB. However, since the factors that ultimately cause complete heart block are not known in patients with BBBB, constant cardiac monitoring is mandatory in the intraoperative and immediate postoperative period.

A case of true bilateral bundle branch block satisfying the criteria of Rosenbaum and Lepeschkin is presented. The basic mechanism is considered to be fixed, incomplete left bundle branch block with intermittent, unstable, rate-related, relatively complete right bundle branch block. This diagnosis should be considered whenever bundle branch block is associated with a prolonged P–R interval.

Article, 信州医学雑誌 21(1): 83-90(1973)

Summary Two cases in which electrocardiographic evidence of right and left bundle branch block occurred on separate occasions are reported. Both developed complete atrioventricular block and the prior evidence of impaired conduction in both bundle branches suggested bilateral bundle branch block as the responsible mechanism. During complete AV block, however, QRS complexes had a supraventricular form incompatible with bilateral bundle branch block. The cases are reported as evidence that bilaterally-impaired bundle branch conduction does not establish bilateral bundle branch block as the mechanism of complete AV block.

His bundle electrograms were recorded in 26 patients with bundle branch block. The interval from the His bundle electrogram to the onset of ventricular activation (H-V) was used as an approximation of conduction time in the left bundle branch in patients with right bundle branch block and of conduction time in the right bundle branch in patients with left bundle branch block. The H-V intervals of patients with right bundle branch block were within the range of those noted in patients with “normal” ventricular activation. The average H-V interval of patients with left bundle branch block was 22 msec. longer than that of patients with right bundle branch block and there was no overlap of individual values. Two patients with alternating LBBB had shorter H-V values during “normal” ventricular activation. Normalization of a bundle branch block pattern by premature atrial stimulation resulted in a shortening of the H-V interval. Two of six patients with right bundle branch block and left axis deviation had prolonged H-V intervals suggesting disease of either the most proximal portion of the left bundle branch or of the posterior-inferior division. The longest H-V values were observed in two patients with prolonged P-R intervals and left bundle branch block suggesting delayed conduction in the right bundle branch. Type I second degree A-V block induced by atrial pacing resulted in blocked impulse transmission proximal to the H potential. In Type II second degree A-V block the cardiac impulse was blocked distal to the H potential presumably in the contralateral bundle branch. Concealed conduction with blocked impulse transmission in the distal portion of the right bundle branch was observed.

The A V conducting system was examined histologically in 13 selected human hearts (7 control and 6 A V block specimens), focusing attention upon normal His bundle (HB) structure, and upon the histopathologic basis of intrahisian block, with supraventricular QRS configuration. HB revealed a poor morphologic identity, often failing to represent the “undivided stem” of the AV pathway, either due to an early partition into separate longitudinal fascicles, or to varied types and sites of bifurcation, without any definite boundary between nonbranching and branching portions. Split His potentials, the distal component of which has been suggested as arising in the proximal bundle branch system, has been found in a case free of HB histologic abnormality. Supra ventricular QRS configuration in escape rhythm was observed in two cases of AV block, not withstanding destruction of the entire His bifurcation, and in experimental bilateral bundle branch block. Pertinent explanations have been suggested. The overall semantic value and usefulness of the current HB nomenclature do not seem to imply, as yet, a precise and constant anatomoclinical correlation.

The clinical course, serial electrocardiograms and His bundle electrograms were reviewed in 15 cases of incomplete bilateral bundle branch block complicating acute myocardial infarction. Fourteen patients had evidence of acute anterior wall myocardial infarction, one had additional evidence of acute inferior wall myocardial infarction and one had acute inferior wall myocardial infarction alone. Incomplete bilateral bundle branch block was manifested as right bundle branch block with left anterior hemiblock in 10 patients and as right bundle branch block with left posterior hemiblock in 4. One patient had right bundle branch block with periods of left anterior and left posterior hemiblock. Nine patients died between 9 hours and 6 weeks after admission; the six surviving patients have been followed up for 3 weeks to 6 months. In all patients a His bundle electrogram was obtained at the time of pacemaker insertion. Of the patients with an abnormal H—Q interval (55 msec or greater), eight died and three survived. Of those with a normal H—Q interval only one died and three survived. Examination of serial electrocardiograms showed that the right bundle branch block disappeared in four patients, of whom one died and three survived. Of the remaining patients with persistent right bundle branch block, eight died and three survived. All five patients with left posterior hemiblock had an abnormal H—Q interval, and four of these patients died. We conclude that in this group of patients, the prognosis is poor for those with an abnormal H—Q interval and persistent right bundle branch block and better for those with a normal H—Q interval and transient right bundle branch block.

Excerpt The mortality rate associated with incomplete bilateral bundle branch block complicating acute myocardial infarction is high (1, 2). The primary cause of death has been thought to be cardio...

Summary Electrocardiograms and His bundle electrograms were presented from a patient with a rare combination of intermittent bilateral bundle branch block. Critical analyses of R-R inervals and evolution of bundle branch block patterns revealed both tachycardia dependent right bundle branch block and bradycardia dependent left bundle branch block. Evaluation of HV intervals on His bundle electrograms suggested an additional possibility of bradycardia dependent conduction delay in the right bundle branch system.

An electrocardiographic diagnosis of bilateral bundle branch block has been made only in rare instances. But the authors presented two cases of this sort and elucidated its mechanisms. The first case could be explained by a transient block in the left bundle branch in the presence of a permanent block in the right bundle branch. A second case is an example which completely fulfils the well-known criteria of ROSENBAUM and LEPESCHKIN.

Summary A patient with sinus rhythm, complete left bundle branch block and 2:1 A-V conduction is described. A ventricular parasystolic rhythm, probably arising from the main left bundle branch system, occasionally gave rise to periods that simulated 3:2 A-V Wenckebach conduction with alternating bundle branch block when the parasystolic rate was approximately one third of the sinus rate. Fusion impulses with complete normalization of the QRS complex were observed. The value of analysis of long rhythm strips and repeated observations is stressed for unraveling complex disorders of cardiac rhythm.

A 74-year-old male is described who demonstrated an intermittent appearance of a right and left bundle branch block with varying P-R intervals. The best explanation of these electrocardiograms is that a bilateral bundle branch block is present. In spite of this conduction defect, the patient remains asymptomatic and has never developed complete heart block.

A 78-year-old female transiently developed atrial fibrillation with complete A-V block and bilateral bundle branch block after she had a quarrel with a newly-appointed, ill-natured nurse. During this period the ECG showed various types of second degree A-V node-ventricular (N-V) block such as multiple second degree N-V block type II, inducing ventricular asystoles of varying durations and second degree N·V block type I (the Wenckebach period) showing a progressive shortening of and then a prompt increase in the RR interval. A special form of second degree N-V block in which a period of progressive shortening of the RR interval was followed by a period of constant RR interval and then terminated by second degree N-V block type II was referred to as second degree N-V block type III. Occasionally, the Wenckebach period in second degree N-V block was followed by a progressive increase in the RR interval which was designated as the counter-Wenckebach period.

The electrophysiologic basis for Mobitz type II second degree heart block was studied in a patient with documented episodes of complete heart block and Stokes-Adams seizures. Recording of His bundle electrograms demonstrated that all atrial impulses were conducted through the atrioventricular (A-V) node to the bundle of His. Nonconducted P waves were blocked distal to the bundle of His. The frequency of blocked beats increased when the rate was accelerated by atrial pacing. Administration of atropine caused more frequent blocked beats, reaffirming the concept that the block occurred beyond the node. It is concluded that Mobitz type II second degree heart block is a manifestation of bilateral bundle branch block. Testing with atropine in this case was useful in distinguishing block in the bundle branches from that in the A-V node.