What is a Right Bundle Branch Block (RBBB)?

Right Bundle Branch Block (RBBB): Patient Explanation

A Right Bundle Branch Block (RBBB) is a heart conduction abnormality where electrical signals are delayed or blocked when traveling through the right bundle branch, causing the right ventricle to contract slightly later than the left ventricle.

What is RBBB?

RBBB occurs when the electrical pathway that carries signals to the right side of your heart is interrupted or blocked. The American College of Cardiology defines RBBB as:

• A heart block in the electrical conduction system specifically affecting the right bundle branch 1
• Characterized by QRS duration ≥120 ms in adults (wider than normal) 1
• Shows a distinctive RSR' pattern in right chest leads (V1-V2) and wide S waves in leads I and V6 1, 2

How the Normal Heart Conducts Electricity

To understand RBBB, it helps to know how your heart normally conducts electricity:

1. Electrical signals start in the upper chambers (atria)
2. Travel through the AV node to the bundle of His
3. The bundle divides into left and right branches that carry signals to each ventricle
4. In normal conduction, both ventricles contract nearly simultaneously

What Happens in RBBB

• When the right bundle branch is blocked, electrical signals must find an alternate, slower path to the right ventricle
• This causes the right ventricle to contract slightly after the left ventricle
• The delay creates the characteristic pattern seen on an ECG

Types of RBBB

There are two main types:

1. Complete RBBB: QRS duration ≥120 ms with characteristic ECG patterns 1
2. Incomplete RBBB: QRS duration between 110-120 ms in adults with similar but less pronounced patterns 1, 3

Causes of RBBB

RBBB can occur:

• In otherwise healthy people with no symptoms or heart disease
• As a result of heart conditions like:
  • Congenital heart defects
  • Heart attacks affecting the right ventricle
  • Cardiomyopathy (heart muscle disease)
  • Pulmonary embolism
  • Heart failure
  • Hypertension
• After heart surgery
• Due to degenerative changes in the conduction system 1

Symptoms

• Most people with RBBB have no symptoms
• Any symptoms typically come from underlying heart conditions, not the RBBB itself
• In rare cases, when combined with other conduction problems, it may cause:
  • Lightheadedness
  • Fainting
  • Shortness of breath

Diagnosis

RBBB is diagnosed through a 12-lead ECG showing:

• QRS duration ≥120 ms
• RSR' pattern in leads V1 or V2 (looks like an "M" shape)
• Wide S waves in leads I and V6 1

Clinical Significance and Follow-up

The significance of RBBB varies:

• Isolated RBBB: Often benign, especially if no other heart problems exist
• RBBB with other conduction problems: May indicate more serious heart disease
• RBBB in athletes: Generally considered benign but may warrant further evaluation 1

Your doctor may recommend:

• Echocardiogram to check heart structure and function
• Exercise stress test
• 24-hour ECG monitoring if symptoms suggest heart rhythm problems 2

Treatment

• Isolated RBBB without symptoms or heart disease: Usually requires no treatment
• RBBB with underlying heart disease: Treatment focuses on the underlying condition
• RBBB with other conduction problems: May require closer monitoring

Prognosis

• Isolated RBBB generally has a good prognosis 2
• When associated with structural heart disease, the prognosis depends on the underlying condition
• RBBB combined with left fascicular blocks (bifascicular block) carries a higher risk of progression to complete heart block 2

When to Contact Your Doctor

Contact your doctor if you develop:

• Unexplained fainting or near-fainting
• Persistent palpitations
• Shortness of breath
• Chest pain
• Unexplained fatigue

Remember that most people with RBBB lead normal lives without limitations, and the condition itself often doesn't require specific treatment.