What is the significance of Right Bundle Branch Block (RBBB) on an electrocardiogram (ECG)?

From the Guidelines

Right bundle branch block (RBBB) on an electrocardiogram (ECG) is a conduction abnormality that requires evaluation for underlying causes, especially in new-onset cases, and may necessitate further cardiac evaluation including echocardiography if accompanied by symptoms or other ECG abnormalities. RBBB is characterized by a widened QRS complex (typically >120 ms), an RSR' pattern (rabbit ear appearance) in leads V1-V3, and wide S waves in leads I and V6. While RBBB may occur in healthy individuals without clinical significance, it can also be associated with underlying heart conditions such as coronary artery disease, cardiomyopathy, pulmonary embolism, or congenital heart defects 1.

Key Considerations

• RBBB can be either complete or incomplete (QRS 100-120 ms)
• The presence of RBBB on ECG increases the risk of left ventricular systolic dysfunction compared to those with completely normal ECGs, although the yield is lower than those patients with LBBB 1
• Echocardiography can identify various structural cardiac abnormalities underlying conduction disturbance, including cardiomyopathy, valvular heart disease, congenital anomalies, tumors, infections, infiltrative processes, immunologically mediated conditions, and diseases of the great vessels and pericardium 1
• Ambulatory electrocardiographic monitoring can be used to document clinically significant arrhythmias in asymptomatic patients with RBBB 1

Management

• No specific treatment is required for isolated RBBB, but evaluation for underlying causes is important, especially in new-onset cases
• If RBBB is found incidentally in an asymptomatic person with no other cardiac abnormalities, regular cardiac follow-up may be sufficient
• However, if accompanied by symptoms or other ECG abnormalities, further cardiac evaluation including echocardiography may be warranted to identify any underlying structural heart disease 1
• The 2018 ACC/AHA/HRS guideline on the evaluation and management of patients with bradycardia and cardiac conduction delay recommends that patients with RBBB or intraventricular conduction delay on ECG have an increased risk of left ventricular systolic dysfunction compared with those with completely normal ECGs 1

From the Research

ECG Interpretation of RBBB

• RBBB on an ECG is characterized by a widened QRS complex and changes in the directional vectors of the R and S waves 2
• The presence of RBBB with a QR pattern in V1 on the ECG has a high positive predictive value for diagnosing cardiac arrest caused by high-risk pulmonary embolism 3
• RBBB can be a criterion for emergent coronary angiography in patients with acute onset chest pain, even in the absence of ST-segment elevations or new left bundle branch block 4

Clinical Significance of RBBB

• RBBB is often regarded as benign, but it can be a sign of underlying cardiac conditions such as pulmonary embolism or acute myocardial infarction 3, 4
• The presence of RBBB does not appear to offer any clinical utility when evaluating patients with suspected acute myocardial infarction, and its presence should not delay emergent coronary angiography in patients with suspected AMI 5
• RBBB can mask anterior ST-elevation on an ECG, making it difficult to diagnose ST-elevation myocardial infarction (STEMI) 6

Diagnostic Considerations

• Patients with RBBB and chest pain should be evaluated for underlying cardiac conditions such as pulmonary embolism or acute myocardial infarction 3, 4
• The ECG findings in patients with RBBB should be carefully interpreted, taking into account the presence of ST-elevation or depression in different leads 6
• Emergent coronary angiography should be considered in patients with suspected AMI who present with RBBB and any ST-elevation in leads V1-3 5