An unusual bundle-branch block

We report a case of right bundle-branch block (RBBB) showing a QRS configuration typical for left bundle-branch block (LBBB) in leads V(5) and V(6). The QRS axis was at +90 degrees, and the QRS duration was 0.14 second. There were wide S waves in leads I and aVL, suggesting at first glance an RBBB, but the QRS morphology in the inferior leads (monophasic R wave with secondary ST-T changes) was more consistent with an LBBB. Lead V(1) suggested an RBBB, whereas leads V(5) and V(6) showed a monophasic R wave as in LBBB; moreover, a negative T wave, typical of LBBB, was present in lead V(5). Placement of the electrodes of leads V(4), V(5), and V(6) 2 intercostal spaces above restored in these leads a QRS configuration suggestive of RBBB. The diagnostic problem was mainly caused by the inferior direction of the QRS axis. Because the electrode of V(6) is normally placed below the electrical center of the heart, namely, on a plane that is not orthogonal to the sagittal plane, a vector directed mainly inferiorly and slightly to the right does not project on the negative part but on the positive of the lead line. For this reason, the S waves normally observed in the left precordial leads with RBBB disappear. The superior displacement of the electrodes "normalizes" the plane upon which the lead lines lie, thereby restoring the expected QRS configuration.     

Two to one right bundle-branch block

A case is reported showing by electrocardiogram at first two to one and later complete right bundle-branch heart-block. No other similar case has been found recorded in the literature, but curves of another patient showing the condition and obtained by Dr. Nils Stenström, of Sweden, are also published herewith.     

Tachycardia-dependent right bundle-branch block with supernormal conduction

This paper reports the case of a 76-year-old man in whom atrial flutter with varying atrioventricular block and intermittent right bundle-branch block was found. This is the first report on tachycardia-dependent right bundle-branch block associated with supernormal conduction in a case of atrial flutter. When an impulse is conducted to the ventricles beyond 0.72 s after a QRS complex of right bundle-branch block configuration, the impulse falls after the abnormally long effective refractor period of the right bundle branch and passes through the right bundle branch. When the conducted impulse occurs within 0.72 s after a QRS complex of right bundle-branch block configuration, the impulse usually falls in the refractory period and is blocked in the right bundle branch; however, only when the impulse occurs 0.48 or 0.49 s after that does it fall in the supernormal period and passes through the right bundle branch. The findings in the present report strengthen our previous suggestion that the presence of supernormal conduction plays an important role in the initiation of reentrant ventricular tachycardia.     

A complete right bundle-branch block masking Brugada syndrome

A 69-year-old man without structural heart disease was admitted for syncope. His electrocardiogram displayed complete right bundle branch (CRBBB). A coved type ST elevation was observed with transient normalization of CRBBB giving rise to a normal QRS. These findings suggest that Brugada syndrome can be masked by CRBBB.     

Abnormal signal-averaged electrocardiograms in patients with incomplete right bundle-branch block

Background and hypothesis: A hypothesis was formulated that regional delayed activation of the right ventricle, as seen in incomplete right bundle-branch (IRBBB) aberrancy, may simulate late potential activity and may be responsible for abnormal signal-averaged electrocardiograms (SAECGs). No previous studies have specifically addressed this issue in this particular group of patients (with IRBBB). Therefore, the aim of the present study was to investigate the incidence of abnormal SAECGs in patients with IRBBB. If this were confirmed, our purpose would further be to investigate ways of reducing the false positive results. Methods: The study group included 53 patients (28 men and 25 women), aged 53 ± 13 years, with no history of previous myocardial infarction or ventricular tachycardia and who had an electrocardiogram (ECG) showing IRBBB. An SAECG was also performed in a control group of 19 age-matched individuals with a normal ECG. Time domain analysis was performed using a band pass filter of 40–250 Hz. The following parameters were considered normal: filtered QRS duration (QRSD) < 114 ms, root mean square of the voltage of the last 40 ms of the QRS complex (RMS) > 20 μV, and the duration of the low amplitude signal (< 40 μV) at the terminal portion of the QRS (LAS) < 38 ms. An SAECG was considered abnormal if any two of these criteria were abnormal. Results: The mean values of the SAECG parameters were: QRSD 101 ± 11 ms, RMS 32 ± 20 μV, LAS 32 ± 12 ms, and noise 0.29 ± 0.13 μV. Abnormal SAECGs with at least two criteria satisfied were present in 16 of 53 (30%) patients compared with 0 (0%) of 19 individuals in the control group (p = 0.02). Abnormal values included the combination of RMS and LAS in 12 patients and all three parameters in 4 patients. However, if the definition of late potentials were limited to the combination of abnormal QRSD and either RMS or LAS values, the incidence of false positive results (4 patients) (7.5%) would be significantly decreased (p = 0.007). At 21 months of follow-up, no arrhythmic events occurred. Conclusions: Delayed terminal conduction observed in IRBBB may cause a high incidence of false positive late potentials on SAECGs. Based on this study, we propose that this can be largely remedied if the optimal criteria for the presence of late potentials in patients with IRBBB always include the combination of QRSD and either RMS or LAS.     

Wolff-Parkinson-White syndrome type B with tachycardia-dependent (phase 3) block in the accessory pathway and in left bundle-branch coexisting with rate-unrelated right bundle-branch block.

A patient with Wolff-Parkinson-White syndrome type B developed 2:1 atrioventricular block resulting from the association of persistent right bundle-branch block with tachycardia-dependent (phase 3) left bundle-branch block. Electrophysiological studies disclosed the coexistence of a tachycardia-dependent (phase 3) block in the accessory pathway. This conduction disturbance was exposed, not by carotid sinus massage as in previous studies, but by pacing-induced prolongation of the interval between two consecutively conducted atrial impulses. Furthermore, the surface electrocardiogram showed, at different times, ventricular complexes resulting from: (1) exclusive atrioventricular conduction through the normal pathway without bundle-branch block; (2) predominant, or exclusive, atrioventricular conduction through a right-sided accessory pathway; (3) exclusive atrioventricular conduction through the normal pathway with right bundle-branch block; (4) exclusive conduction through the normal pathway, with left bundle-branch block; (5) fusion between (1) and (2); and finally, (6) fusion between (2) and (3) However, QRS complexes resulting from simultaneously occurring Wolff-Parkinson-White syndrome type B and left bundle-branch block could not be identified. Future electrophysiological investigations should re-evaluate the criteria used to diffrentiate between true and false patterns of Wolff-Parkinson-White syndrome type B coexisting with left bundle-branch block.     

Familial, isolated, complete right bundle-branch block.

An electrocardiographic study of the families of two children with isolated complete right bundle-branch block is presented. Several cases of classical complete right bundle-branch block were disclosed (17/69 and 3/22 respectively) in three generations of the two families. Personal interviews and parish registers showed that the two families were related, being descendants 8 generations back from a glass-blower who has emigrated to Sweden in the eighteenth century. It is concluded that complete right bundle-branch block can be an autosomal, genetic anomaly which is inherited dominantly but with reduced penetrance and/or expressivity.     

His bundle recordings in right bundle-branch block coexisting with iatrogenic right ventricular pre-excitation

Iatrogenic right ventricular pre-excitation failed to abolish right bundle-branch block in two patients. When `exclusive' His bundle pacing was performed, the QRS complexes, St-V, and St-LVE intervals were similar to the ventricular deflections, H-V, and V-LVE (intervals) recorded during sinus rhythm. `Exclusive' pacing of the ordinary muscle at the right ventricular inflow tract produced a complete left bundle-branch block pattern without abnormal left axis deviation. Pacing of both His bundle and ordinary muscle yielded combination complexes in which the right bundle-branch block pattern persisted.     

Histological substrate of ventricular tachycardias of the right bundle-branch block type (sensitive to verapamil)

In order to clarify the anatomic substrate of idiopathic ventricular tachycardia of right bundle-branch block morphology, responsive to verapamil, two patients with this type of arrhythmia were evaluated using hemodynamic studies, right ventricular endomyocardial biopsy as well as electrophysiological and pharmacological studies. Pressures, right and left ventriculography and coronary angiography were normal in both patients. Case 1 showed a prolonged sinus node recovery time and a histological pattern which was compatible with healed myocarditis. Case 2 presented a complete right bundle-branch block, intra-His conduction defects and histological features of aspecific cardiomyopathy. Our results underline the presence of diffuse ventricular histologic changes in patients with idiopathic ventricular tachycardia of right bundle-branch block morphology. These histologic changes seem unable to interfere with cardiac pump function but are sufficient to create significant abnormalities of impulse formation and conduction.     

Significance of complete right bundle-branch block when an isolated finding. An echocardiographic study.

Twenty-seven patients with complete right bundle-branch block as the only abnormal finding were studied using high speed M-mode echocardiography to determine the effect of the electrical delay on the mechanical events of right ventricular systole. Pulmonary valve opening (PVOm) was delayed in all cases. In some the delay was mainly between mitral valve closure (MVC) and tricuspid valve closure (TVC), and this was designated proximal block. In the others the main delay was between tricuspid valve closure and pulmonary valve opening and this was designated distal block. The patients were divided into those with proximal and those with distal block by calculating the ratio TVC-PVOm/MVC-TVC. Twelve out of 13 of those with distal delay but only one out of 14 of those with proximal delay had episodes of syncope or near syncope. These results are consistent with previous theories about the pathophysiology of right bundle-branch block. Echocardiography may offer a non-invasive method to estimate the prognosis in isolated right bundle-branch block.