Right Bundle Branch Block: Current Considerations

RBBB, a pattern seen on the 12-lead ECG, results when normal electrical activity in the His-Purkinje system is interrupted for some reason. The normal sequence of activation is altered in RBBB, with a resultant characteristic appearance on the ECG manifest by a widened QRS complex and changes in the directional vectors of the R and S waves. This ECG pattern is often seen in clinical practice and generally regarded as benign. The anatomy, epidemiology, causes, symptoms, ECG findings and diagnosis, differential diagnosis in ECG, treatment, complications, prognosis, with respect to RBBB are outlined here, demonstrating some typical ECGs of RBBB.     

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)     

左束支区域起搏可改善右束支阻滞的心电图表现

目的:旨在观察左束支区域起搏(LBBAP)纠正右束支阻滞(RBBB)的临床效果及心电图特点.方法:本研究为单中心、前瞻性观察性研究,纳入2018年4月至2019年12月间入院有心室起搏指征,存在基线RBBB图形且QRS波群时限≥120 ms、左心室射血分数>50％并接受LBBAP的患者,分析LBBAP纠正RBBB的临床...     

Total Masquerading Bundle Branch Block

We report a case of 82‐year‐old female with total masquerading bundle branch block. We discuss the problems with ECG analysis.     

Right Bundle Branch Block on Alternate Beats during Acute Pulmonary Embolism

The electrocardiogram of a patient with acute pulmonary embolism showed right bundle branch block (RBBB) on alternate beats; following thrombolysis, the pattern evolved to persistent RBBB and eventually to normal conduction. Analysis of serial tracings suggested that the mechanism of RBBB alternans was tachycardia‐dependent bidirectional bundle branch block, caused by prolongation of both anterograde and retrograde refractory periods (RPs) of the right bundle branch (RBB). The sinus impulse found the RBB refractory, and was conducted over the left bundle branch only, depolarizing the left ventricle and then attempting to penetrate retrogradely the RBB; at that time, however, the RBB was still refractory. When a QRS complex had a RBBB configuration, therefore, the RBB was not depolarized; the ensuing sinus impulse found the RBB fully responsive as a consequence of the long period intervening between two successive depolarizations, and resulted in normal intraventricular conduction. With right ventricular afterload decrease, the recovery of RBB anterograde and retrograde excitability was asynchronous, since the retrograde RP became normal earlier than the anterograde one. In accordance with the relatively short retrograde RP, the RBB was retrogradely invaded by the transseptal impulse coming from the left ventricle; this “shifted to the right” the anterograde RP of the RBB. The RBB, thus, was still refractory to the next sinus impulse, and RBBB again occurred; the RBB, thus, was once more depolarized retrogradely, and this led to perpetuation of RBBB. Finally, intraventricular conduction became normal owing to full normalization of RBB anterograde and retrograde refractoriness. Ann Noninvasive Electrocardiol 2011;16(3):311–314     

Utilization of Retrograde Right Bundle Branch Block to Differentiate Atrioventricular Nodal from Accessory Pathway Conduction

Introduction: Defining whether retrograde ventriculoatrial (V-A) conduction is via the AV node (AVN) or an accessory pathway (AP) is important during ablation procedures for supraventricular tachycardia (SVT). With the introduction of ventricular extrastimuli (VEST), retrograde right bundle branch block (RBBB) may occur, prolonging the V-H interval, but only when AV node conduction is present. We hypothesized that when AP conduction was present, the V-A interval would increase less than the V-H interval, whereas with retrograde nodal conduction, the V-A interval would increase at least as much as the V-H interval.
Methods and Results: We retrospectively reviewed the electrophysiological studies of patients undergoing ablation for AVN reentrant tachycardia (AVNRT) (55) or AVRT (50), for induction of retrograde RBBB during the introduction of VEST, and the change in the measured V-H and V-A intervals. Results were found to be reproducible between independent observers. Out of 105 patients, 84 had evidence of induced retrograde RBBB. The average V-H interval increase with induction of RBBB was 53.7 ms for patients with AVRT and 54.4 ms for patients with AVNRT (P = NS). The average V-A interval increase with induction of RBBB was 13.6 ms with AVRT and 70.1 ms with AVNRT (P < 0.001). All patients with a greater V-H than V-A interval change had AVRT, and those with a smaller had AVNRT.
Conclusions: Induction of retrograde RBBB during VEST is common during an electrophysiological study for SVT. The relative change in the intervals during induction of RBBB accurately differentiates between retrograde AVN and AP conduction.     

Retrograde Purkinje Potential Activation During Sinus Rhythm Following Catheter Ablation of Idiopathic Left Ventricular Tachycardia

Idiopathic Left VT and Purkinje Potentials . We describe two patients with idiopathic left ventricular tachycardia that were cured by radiofrequency catheter ablation. Tachycardia was inducible by ventricular stimulation and was verapamil sensitive. Two distinct presystolic potentials (PI and P2) were recorded during tachycardia in the mid-septal or inferoapical area, but only one potential (P2) was recorded during sinus rhythm. After catheter ablation at this site, the PI potential was noted after the QRS complex during sinus rhythm, while the P2 was still observed before the QRS complex. The P1 potential showed a decremental property during atrial or ventricular pacing. These data suggest that Purkinje tissue with decremental properties was responsible for the tachycardia mechanism, and that the reentry circuit involving this tissue is likely to be of considerable size.     

Catheter Ablation of the Left Bundle Branch for the Treatment of Sustained Bundle Branch Reentrant Ventricular Tachycardia

Sustained Bundle Branch Reentrant VT. Radiofrequency catheter ablation of the left bundle branch (LBB) was attempted in a patient with sustained bundle branch reentry. During sinus rhythm, the QRS had a complete LBB block pattern, and the LBB was activated retrogradely (transseptal). Ablation of the LBB eliminated inducibility of the tachycardia, while the QRS complex and the duration of the HV interval (70 msec) remained unchanged. Successful ablation of the LBB eliminated bundle branch reentry and yet maintained the anterograde conduction properties of the His-Purkinje system, obviating implantation of a permanent pacemaker.     

Brugada波与右束支阻滞的心电图和心电向量图的比较

目的了解Brugada波与右束支阻滞的心电图和心电向量图的异同。方法将15例Brugada波患者与20例右束支阻滞患者和20例正常心电图者进行心电图和心电向量图比较。结果右束支阻滞和Brugada波患者的心电图在V1～V2导联都可呈M型或rsR’型,但两者的ST段改变不同,右束支阻滞的ST向量背离终末泪点密集处,而Brugada波的ST向量却指向终末泪点密集处;两者在心电向量图上均见QRS环的终末泪点密集,但持续时间、方位和形态不同。结论Brugada波不是真正的右束支阻滞;其ST-T改变是与患者特定离子通道基因变异、心室肌的电学异质性有关的一种特殊的功能性改变。     

Bundle branch reentrant ventricular tachycardia with two distinct components of QRS complex due to simultaneous dual transseptal conduction

We report the case of a patient with bundle branch reentrant ventricular tachycardia having two distinct components of the QRS complex due to simultaneous dual transseptal conduction. The macroreentrant circuit consisted of anterograde conduction down the left bundle branch and retrograde conduction up the right bundle branch. Extensively injured myocardium in the interventricular septum isolated the two separate transseptal passages, which exhibited a "fast" and "slow" conduction property, respectively. The QRS configuration resulted from a wavefront propagating from the left bundle branch via "fast" transseptal conduction, followed by another more delayed wavefront propagating via "slow" transseptal conduction, which played an important role in determining this unique QRS morphology.     

Profound Independent Effects of Left Bundle Branch Block and Heart Rate During Supraventricular Tachycardia

Left bundle branch block (LBBB) has negative hemodynamic effects. In the same patient, profound hypotension occurs during supraventricular tachycardia with LBBB but not at the same rate in the absence of LBBB. At slower rates, blood pressure is similar with and without LBBB.     

Pulsus Alternans Caused by 2:1 Left Bundle Branch Block

Pulsus alternans was caused by 2:1 left bundle branch block in a patient with a left ventricular ejection fraction of 50% and normal coronary arteries. The observations documented the profound depressant hemodynamic effect of complete left bundle branch block in the setting of minimal systolic left ventricular function.     

Radiofrequency Catheter Ablation of the Left Bundle Branch in a Canine Model

Left Bundle Branch Ablation. Introduction: Transcatheter ablation of the left bundle branch may be considered for management of selected macroreentrant ventricular tachycardias. Left bundle ablation can also change the sequence of left ventricular contraction and may simulate pacing in hypertrophic obstructive cardiomyopathy. The purpose of this study was to determine electrophysiologic and anatomic parameters for successful selective transcatheter left bundle ablation in a canine model. Methods and Results: A catheter was advanced to the left ventricular apex and the tip deflected toward the septum, until a discrete left bundle potential (LBP) was found. Radiofrequency (RF) energy was then applied until left bundle branch block or complete AV block occurred. In 29 (85%) dogs, an LBP (mean LBP-V 16 ± 3 msec; range 10 to 20 msec) was identified resulting in successful left bundle ablation. In 5 (15%) dogs, a similar potential (mean potential-V 28 ± 4 msec; P = 0.001 vs LBP-V) was identified, but RF energy application produced complete AV block. The A:V electrogram ratio at the successful LBP ablation site was < 1:10 in all 29 dogs successfully ablated, but only 2 (40%) of 5 dogs in the unsuccessful group (P = 0.0017). In 4 successfully ablated dogs, the right bundle potential was mapped and complete AV block was created by RF energy application, confirming that the left bundle was completely ablated. In 9 dogs, the left bundle and AV junction were sequentially ablated with 1 lesion at each site. Postmortem examination showed 2 discrete lesions 1.2 ± 0.7 cm apart. Conclusions: Selective transcatheter left bundle ablation was successfully guided by the LBP. The distance between the AV junction and the main left bundle was 1.2 cm in this canine model. An A:V ratio < 1:10 and an LBP-V time < 20 msec appear to minimize the risk of AV block. Prudent use of similar techniques may cure macroreentrant ventricular tachycardias and reduce the need for permanent pacing in hypertrophic obstructive cardiomyopathy.     

The Mischievous Bundle: A Case of Varying Degrees of Right Bundle Branch Block on Alternate Beats during Exercise Stress Testing

A 78‐year‐old male was referred for exercise stress testing. He developed incomplete right bundle branch block during first stage of exercise and later on developed incomplete and complete right bundle branch block on alternate beats (2:1). During first minute of recovery he developed complete right bundle branch block on all beats (1:1). At 3 minutes of recovery, baseline electrocardiographic pattern was resumed. Variable degree of right bundle branch block on alternate beats is a rare phenomenon. The plausible mechanisms responsible for this phenomenon are being discussed.     

急性心肌梗死与束支传导阻滞新认识

束支传导阻滞是急性心肌梗死的心电图常见合并情况。由于束支传导阻滞显著干扰急性心肌梗死患者的心电图表现,易导致临床识别困难和误诊;且束支传导阻滞对心肌梗死患者预后具有重要的预测价值。本综述详细阐明了急性心肌梗死时合并束支传导阻滞的诊断及预后意义。