Causes of Bundle Branch Block
Causes of bundle branch block relate to conditions that affect the heart’s electrical conduction system, especially the ventricles. The most common causes of bundle branch block include heart disease, structural abnormalities, scar tissue, high blood pressure, and, in some cases, unknown reasons.
Right bundle branch block (RBBB) is often associated with:
- Congenital heart abnormalities such as atrial septal defect
- Pulmonary embolism or chronic lung disease
- Right ventricular enlargement due to pressure overload
- A normal variation in otherwise healthy individuals
Left bundle branch block (LBBB) is more likely to be caused by:
- Coronary artery disease (especially prior heart attacks)
- Cardiomyopathy
- Aortic stenosis
- Long-standing high blood pressure
- Age-related degeneration of the conduction system
LBBB tends to indicate more serious underlying heart conditions and is often associated with a higher risk of heart failure, especially if the left ventricle does not pump efficiently.
Other causes common to both RBBB and LBBB include:
- Infections such as myocarditis
- Trauma to the chest or heart (including during cardiac surgery)
- Electrolyte imbalances
- Certain medications or procedures (e.g. catheter placement)
Causes of Bundle Branch Block
In some cases, no specific cause is found, and the block may be an incidental finding without immediate health concerns.
Understanding the causes of bundle branch block helps doctors decide whether additional tests are needed and what treatment, if any, is appropriate. It also allows for risk assessment regarding potential heart rhythm problems or structural heart disease.
What Causes Bundle Branch Block?
Bundle branch block occurs when the electrical impulses that control heartbeats are delayed or blocked along the heart’s conduction pathways. This is usually caused by underlying heart conditions or structural changes. Right bundle branch block (RBBB) may result from congenital heart defects like atrial septal defect, chronic lung conditions, or right ventricular enlargement. In some cases, RBBB appears in healthy individuals without any underlying disease. Left bundle branch block (LBBB), on the other hand, is more often linked to serious issues such as coronary artery disease, past heart attacks, cardiomyopathy, aortic stenosis, or long-standing hypertension. Degeneration of the heart’s electrical system due to ageing can also contribute.
Shared and Unidentified Causes
There are causes common to both RBBB and LBBB, including infections like myocarditis, trauma or injury to the chest, complications from cardiac procedures, electrolyte imbalances, or the side effects of certain medications. Occasionally, no clear cause is found, and the block is discovered incidentally during a routine ECG. Identifying the underlying cause is vital, as it helps determine whether further investigation or treatment is needed. In the case of LBBB, especially, it may indicate an increased risk of heart failure or other serious complications.
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