Right Bundle Branch Block (RBBB) on ECG: What Does It Mean?

Introduction

Right Bundle Branch Block (RBBB) is a condition in which electrical conduction through the right bundle branch of the heart is delayed or blocked. This results in a characteristic pattern on an electrocardiogram (ECG). RBBB can be benign or associated with underlying heart disease.

Understanding the Electrical System of the Heart

The heart's electrical system controls the heartbeat. It consists of the sinoatrial (SA) node, the atrioventricular (AV) node, and the His-Purkinje system, including the right and left bundle branches. - In a normal heart, electrical impulses travel rapidly through both bundle branches, ensuring synchronized contraction of the ventricles. - In RBBB, the right bundle branch is either partially or completely blocked, causing a delayed activation of the right ventricle.

ECG Characteristics of RBBB

On an ECG, RBBB typically shows: - QRS duration ≥ 120 ms (prolonged QRS) - RSR’ pattern (M-shaped or rabbit ears) in leads V1-V2 - Slurred S wave in leads I and V6 - Delayed right ventricular activation

Causes of RBBB

RBBB can be benign or associated with underlying heart conditions: - Benign Causes: - Can occur in healthy individuals without underlying disease. - Pathological Causes: - Ischemic heart disease (e.g., coronary artery disease, heart attack) - Hypertension and left ventricular hypertrophy - Pulmonary embolism - Congenital heart disease (e.g., atrial septal defect) - Myocarditis or cardiomyopathy

Symptoms and Clinical Significance

• Asymptomatic Cases: Many people with RBBB have no symptoms and require no treatment.
• Symptomatic Cases: If RBBB is associated with heart disease, symptoms may include dizziness, fatigue, or fainting.

Diagnosis and Management

• Diagnosis: ECG is the primary tool. Further tests may include echocardiography, stress testing, or cardiac MRI.
• Management Depends on Cause: If due to heart disease, the underlying condition must be treated.
• Pacemaker Therapy: In rare cases, if RBBB is associated with conduction system disease and leads to heart block, a pacemaker may be needed.

Conclusion

RBBB is often benign but can indicate underlying heart conditions. If detected on an ECG, further evaluation may be necessary to rule out associated diseases.

Source recommendations

1. American Heart Association Guidelines on ECG Interpretation

1. https://www.heart.org/en/health-topics/heart-attack/diagnosing-a-heart-attack/electrocardiogram-ecg-or-ekg
2. https://www.ahajournals.org/doi/10.1161/circulationaha.108.191095
3. https://www.heart.org/-/media/files/affiliates/mwa/kansas-city/kc-cardiac-and-stroke-symposium/2020-event-documents/cardiac-presentations/2-ecg-hockstad.pdf?la=en
4. https://www.ahajournals.org/doi/10.1161/circulationaha.108.191098
5. https://pubmed.ncbi.nlm.nih.gov/19281931/

2. European Society of Cardiology Guidelines on Conduction Disorders

1. https://www.escardio.org/Guidelines/Clinical-Practice-Guidelines/Cardiac-Pacing-and-Cardiac-Resynchronization-Therapy
2. https://www.jacc.org/doi/10.1016/j.jacc.2020.08.050
3. https://www.escardio.org/static-file/Escardio/Subspecialty/EHRA/Research/surveys%20&%20Scientific%20initiatives/DOC/euac027.pdf
4. https://www.jacc.org/doi/10.1016/j.jacc.2019.07.014
5. https://www.sciencedirect.com/science/article/pii/S1547527124036130