Right Bundle Branch Block: Current Considerations

Authors, Journal, Affiliations, Type, DOI

• Author: Takanori Ikeda
• Journal: Current Cardiology Reviews (Curr Cardiol Rev), 2021;17(1):24–30
• Affiliation: Department of Cardiovascular Medicine, Toho University Faculty of Medicine / Toho University Omori Medical Center, Tokyo, Japan
• Type: Review article
• DOI: https://doi.org/10.2174/1573403X16666200708111553

Overview

Comprehensive clinical review of RBBB covering anatomy, epidemiology, ECG diagnosis, differential diagnosis, treatment, and prognosis. RBBB is generally benign in isolated form (2–3% general population prevalence, strongly age- and sex-dependent), but is an independent predictor of all-cause mortality when combined with cardiovascular disease. Key distinctions include: RBBB does not interfere with MI diagnosis (initial 30–40 ms normal); Brugada syndrome is the most important pseudo-RBBB that must be excluded; CRT generally does not benefit RBBB patients, though subgroups with LAFB or prolonged PR may respond.

Keywords

Right bundle branch block, His-Purkinje system, widened QRS complex, conduction disturbance, ECG, 12-lead

Key Takeaways

1. Anatomy and Physiology

Right Bundle Branch Anatomy:

• Thin, long, discrete structure consisting of fast-response Purkinje fibers
• Upper 1/3: travels along RV side of interventricular septum near endocardium
• Middle 1/3: travels deeper in muscular portion of septum
• Lower 1/3: returns near endocardium; ramifies near base of right anterior papillary muscle with fascicles going toward septum and free wall of RV

Blood Supply:

• Primarily from septal branches of the left anterior descending (LAD) coronary artery (especially initial length)
• Collateral supply from right or left circumflex coronary artery depending on dominance

Pathophysiology:

• In RBBB: RV is not directly activated via right bundle branch; LV is normally activated via left bundle branch
• RV depolarization occurs via trans-myocardial spread from LV → slower conduction → QRS widening
• Initial 30–40 ms of QRS is normal (septal activation preserved) — important for MI diagnosis

2. Epidemiology

• General population prevalence: 2–3%
• Prevalence increases with age and is higher in men
• Swedish study (Eriksson 1998, men born 1913): Cumulative incidence 1% at age 50; 18% at age 80
• Copenhagen City Heart Study (Bussink 2013; n = general population, no prior CV disease): 1.4% in men, 0.5% in women; ranges from 0.6% (women <40 yr) to 14.3% (men >80 yr)
• Women's Health Initiative (mean age 63 yr; 19% with CVD): RBBB prevalence 1.3% at baseline
• NHANES-III (mean age 61 yr; 53% female; 16% with CAD at baseline): RBBB prevalence 2.3%
• Incomplete RBBB: ~3× more common than complete RBBB; less age-associated; often seen in healthy individuals
• Contrast with LBBB: LBBB rarely occurs in a normal heart; RBBB can occur as a normal variant

3. Causes

• Normal variant / idiopathic — most common cause; no underlying disease
• Hypertension — associated with high systolic BP but not consistently with other CV risk factors
• Structural cardiac disorders: ischemic heart disease, cardiomyopathy, myocarditis, valvular disease, congenital heart disease
• Pulmonary disease: pulmonary embolism (acute new RBBB → consider PE), pulmonary hypertension
• Brugada syndrome — causes a pseudo-RBBB ECG pattern (see differential section)
• Iatrogenic: right heart catheterization of basal ventricular septum can induce RBBB

4. Symptoms

• Most patients are asymptomatic — commonly identified incidentally on 12-lead ECG during health checkup
• Rarely: presyncope as precursor to advanced AV block onset

5. ECG Diagnosis

5.1 Complete RBBB (AHA/ACCF/HRS 2009 Criteria)

1. QRS ≥120 ms (adults)
2. rsr', rsR', or rSR' in V1 or V2:
   • rSR' most commonly seen
   • rsR' ("bunny ear" pattern) rarely observed
3. S wave duration > R wave duration, or S wave >40 ms, in leads I and V6
4. R peak time >50 ms in V1; normal in V5 and V6
5. ST-T changes: discordant to terminal QRS vector — inverted T wave in V1–V2 (terminal R'); upright T wave in I and V6 (terminal S wave)
6. Concordant T wave = suggestive of ischemia or MI

Important Point on MI Coexistence:

• RBBB does NOT interfere with MI diagnosis using Q and R wave criteria because the initial 30–40 ms vectors are essentially normal
• QSR' pattern in V1–V2 in complete RBBB = acute anteroseptal MI coexistent with RBBB

5.2 Incomplete RBBB

• QRS 100–119 ms in V1 and V2 with same RBBB morphology
• All other criteria (ST-T) same as complete RBBB
• Can be a normal variant, especially if V1 is recorded higher/more right than usual and R' <20 ms

5.3 Rate-Dependent RBBB

• RBBB pattern appears intermittently at fast heart rates; resolves with slowing
• Can be mistaken for VT or accelerated idioventricular rhythm

5.4 RBBB Combined with Other Conduction Disturbances

• Bifascicular block: RBBB + LAFB (most common combination in clinical practice); or RBBB + LPFB; or RBBB + LSFB
• Trifascicular block: Bifascicular block + 1st-degree AV block
• Clinical relevance: bifascicular block with syncope → EPS; HV ≥70 ms → PPM (see concepts/Atrioventricular-Block)

6. Differential Diagnosis

6.1 Ventricular Arrhythmias

• VT (rate >100 bpm) and accelerated idioventricular rhythm (rate <100 bpm) can mimic RBBB morphology
• Distinguishing features: ventricular arrhythmias → AV dissociation; RBBB → P waves precede QRS (supraventricular command)

6.2 Ventricular Pacing

• RV pacing → LBBB pattern on ECG (not RBBB)
• Biventricular pacing → complex QRS that can occasionally resemble RBBB
• Key identifier: pacemaker spikes precede QRS in paced rhythms

6.3 Brugada Syndrome (pseudo-RBBB)

• Brugada ECG = pseudo-RBBB (not true RBBB); characterized by:
  • Coved ST-segment elevation with inverted T wave in V1–V2
  • Widened S wave in I and V6 is typically absent (key distinguishing feature from true RBBB)
  • Spontaneous ECG changes are common (dynamic pattern)
• Brugada patients can occasionally have true RBBB, in which case the Brugada pattern is concealed within the RBBB morphology
• Chiale maneuver: Right apical ventricular pacing with appropriately timed A-V intervals can unmask the Brugada ECG pattern when it is concealed by true RBBB
• Concordant ST-T changes in right precordial leads should always raise suspicion for Brugada

7. Treatment

• Chronic RBBB without symptoms: No treatment required
• New RBBB: Treat underlying cause (coronary revascularization for ischemic disease; anticoagulation/fibrinolysis for PE)
• RBBB with syncope + advanced 2nd-degree AV block: Pacemaker implantation (rarely needed)
• CRT in RBBB: Generally, no clinical benefit from CRT in RBBB patients with heart failure
  • Exception: Specific ECG patterns — RBBB + LAFB and RBBB + prolonged PR interval — may represent conditions where CRT provides benefit (Atwater 2017, Houston 2018)

8. Complications

• Progression to 3rd-degree (complete) AV block → risk of SCD; less common with RBBB than LBBB
• Iatrogenic RBBB during right heart catheterization of basal ventricular septum

9. Prognosis

• Isolated RBBB without underlying heart disease: Generally favorable prognosis; does not imply increased risk in healthy individuals
• RBBB + cardiovascular disease: Independent predictor of all-cause mortality (Hesse 2001; Freedman 1987; Barsheshet 2011; Rasmussen 2019; Xiong 2015 meta-analysis of prospective cohort studies)
• Large cohort studies and systematic reviews show increased mortality with complete RBBB in patients with CAD or heart failure
• Prognosis significantly related to type and severity of underlying cardiac disease and presence of other conduction disturbances (bifascicular block, AV block)
• Women's Health Initiative (n = ~94,000 women): mortality risk associated with RBBB and related repolarization abnormalities (Zhang 2012)

Limitations of the Document

• Concise narrative review; no systematic review/meta-analysis methodology
• Limited depth on specific clinical scenarios (e.g., acute new RBBB in STEMI management, RBBB in structural CHD)
• CRT section is brief with only two recent references; the RBBB CRT evidence base is weak overall
• No formal grading of evidence

Key Concepts Mentioned

• concepts/RBBB — dedicated RBBB clinical concept page (new page)
• concepts/ECG-Conduction-Disturbances — RBBB ECG criteria per AHA 2009; bifascicular/trifascicular block
• concepts/Atrioventricular-Block — RBBB + bifascicular block + syncope → EPS/PPM
• concepts/Cardiac-Resynchronization-Therapy — RBBB generally no CRT benefit; exceptions: LAFB + RBBB, long PR
• concepts/Permanent-Pacing-Indications — RBBB + syncope + advanced AV block → pacemaker
• entities/Brugada-Syndrome — pseudo-RBBB; Chiale maneuver; concealed Brugada in true RBBB

Key Entities Mentioned

• entities/Brugada-Syndrome — Brugada as pseudo-RBBB; distinction from true RBBB; Chiale maneuver

Wiki Pages Updated

• Created: wiki/sources/rbbb-ccr-2021.md
• Created: wiki/concepts/RBBB.md
• Updated: wiki/sourceindex.md
• Updated: wiki/wikiindex.md
• Updated: wiki/concepts/ECG-Conduction-Disturbances.md — RBBB epidemiology, prognosis, Brugada pseudo-RBBB distinction
• Updated: wiki/entities/Brugada-Syndrome.md — Chiale maneuver, concealed Brugada in true RBBB, pseudo-RBBB clarification
• Updated: wiki/concepts/Cardiac-Resynchronization-Therapy.md — RBBB CRT exception subgroups