What are the symptoms of Right Bundle Branch Block (RBBB)?

Symptoms of Right Bundle Branch Block (RBBB)

Right Bundle Branch Block (RBBB) is typically asymptomatic in the absence of underlying structural heart disease. Most patients with isolated RBBB have no symptoms directly attributable to the conduction abnormality itself 1.

Clinical Presentation of RBBB

Common Presentation

• Asymptomatic detection: RBBB is most commonly discovered incidentally during routine ECG screening or when an ECG is performed for other reasons 1
• No direct symptoms: Isolated fascicular and bundle branch blocks rarely cause symptoms on their own 1

When Symptoms May Occur

RBBB may be associated with symptoms in specific circumstances:

1. When associated with underlying heart disease:

   • RBBB may be a marker for underlying structural heart disease 1
   • Symptoms in these cases are typically due to the underlying condition rather than the RBBB itself

2. Exercise-related findings:

   • Decreased functional aerobic capacity 2
   • Slower heart rate recovery after exercise 2
   • More frequent dyspnea during exercise compared to individuals without RBBB 2

3. In specific clinical scenarios:

   • When RBBB is part of bifascicular block (RBBB plus left anterior or posterior fascicular block), it may indicate more extensive conduction system disease 1
   • When RBBB occurs with a QR pattern in V1, it may be associated with pulmonary embolism in acute settings 3

Clinical Significance and Evaluation

Risk Assessment

• Recent evidence suggests RBBB may not be entirely benign as previously thought
• In patients without known cardiovascular disease, RBBB has been associated with:
  • Increased risk of all-cause mortality 2
  • Increased risk of cardiovascular-related mortality 2
  • Higher prevalence of hypertension 2

When to Consider Further Evaluation

According to guidelines, further evaluation should be considered when RBBB is detected in:

1. Athletes with RBBB:

   • Cardiac evaluation with history, physical examination, ECG, echocardiogram, and stress test is recommended 1
   • Ambulatory monitoring may be warranted in selected cases to rule out progression to higher-degree AV block 1

2. Patients with syncope and RBBB:

   • RBBB is considered a risk factor for arrhythmic syncope 1
   • Further evaluation is recommended to exclude intermittent high-degree AV block 1

3. Patients with bifascicular block:

   • Ambulatory ECG monitoring may be considered to document suspected higher-degree AV block 1

Key Points to Remember

• The ECG diagnosis of complete RBBB includes:

  1. QRS duration ≥120 ms in adults
  2. rSR' pattern in leads V1 and/or V2
  3. S wave duration greater than R wave or >40 ms in leads I and V6
  4. Normal R peak time in leads V5 and V6 but >50 ms in lead V1 1

• Incomplete RBBB has the same morphology criteria but with QRS duration between 110-119 ms 1

• While RBBB itself rarely causes symptoms, it may be a marker for underlying cardiovascular disease and warrants appropriate evaluation, especially when accompanied by symptoms or other conduction abnormalities 1.