Bundle Branch Block: What to Know

Medically Reviewed by James Beckerman, MD, FACC on September 04, 2023
2 min read

Impulses, or electrical signals, travel through both the left and right chambers of your heart to make it pump. But if the pathway is blocked, the impulses may move slower than normal or irregularly. This is called a bundle branch block.

The name comes from the wire-like branch that carries these impulses and splits into left and right bundles. There are two types:

  • Right bundle branch block (RBBB)
  • Left bundle branch block (LBBB)

Your risk of having a bundle branch block goes up with age or if you have other health issues.

This is the most common type. If your cardiologist (a heart doctor) spots RBBB through a test called an electrocardiogram (EKG), they may look for underlying heart or lung conditions that could be causing the issue.

These include:

If your cardiologist spots LBBB on an EKG, they may run tests to figure out the cause. Unlike RBBB, left bundle blocks are more often a sign of tissue damage.

Many of them are the same as RBBB and can include:

If you don’t already have heart disease, heart disease symptoms, or other electrical blocks, you may not need treatment. But your cardiologist will look into treatment options if you’ve had:

Blocks typically form on one side. But if both branches are blocked, it may disrupt your heart’s electrical activity. Tell your doctor if you’re having any of these symptoms:

LBBB can make it difficult for your doctor to diagnose other heart conditions. These include:

Left ventricular hypertrophy (LVH). A condition where the walls of your heart’s left pumping chamber become thick.

Ischemia. This condition reduces blood flow to the heart.

Always tell a new doctor if you’ve been diagnosed with LBBB. This will help them do a better job of spotting changes in your heart. For example, if you have LHV, your doctor may need to do a stress test with medicine instead of exercise.

It’s also a good idea to carry a copy of your EKG that shows you have LBBB in case of an emergency, like a heart attack. That way, the doctors and nurses know and can give you the right treatment.