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Bundle Branch (Heart) Block

A bundle branch is part of the electrical pathway of the heart that delivers electrical impulses to the ventricles of the heart. The bundle divides or branches into a right bundle and the left bundle. The bundles take the impulse through the ventricles (bottom chambers) to cause them to contract. Bundle branch block is a condition in which there's a delay or obstruction along the pathway.

For the left and right ventricles to contract at the same time, an electrical impulse must travel down the right and left bundle branches at the same speed. When there's a block in one of the bundle branches, the impulses must travel to the affected side by a detour that slows them down. That means one ventricle contracts a fraction of a second slower than the other, creating irregular heartbeats.

Although bundle branch block itself often requires no direct treatment, you'll need treatment of any underlying health condition that could cause bundle branch block, such as coronary heart disease. The block can be caused by coronary artery disease, cardiomyopathy, or valve disease. Right bundle branch block may also occur in a healthy heart.

Doctors can easily diagnose bundle branch block with an electrocardiogram (EKG or ECG).

What are the symptoms of bundle branch block?


In most people, bundle branch block doesn't cause any symptoms. For those people who do have signs and symptoms, they may include:

  • Fainting
  • Dizziness
  • Slow heart rate (brachycardia)