Bundle branch block

Bundle branch block is a condition in which there's a delay or obstruction along the pathway that electrical impulses travel to make your heart beat. The delay or blockage may occur on the pathway that sends electrical impulses to the left or the right side of your heart.

Bundle branch block sometimes makes it harder for your heart to pump blood efficiently through your circulatory system.

There's no specific treatment for bundle branch block itself. However, any underlying health condition that caused bundle branch block, such as heart disease, will need to be treated. Sometimes, bundle branch block is associated with other problems in the heart's electrical system that can lead to dangerously slow heartbeats that need treatment with a temporary or permanent pacemaker.

Symptoms Causes Complications Prevention

In most people, bundle branch block doesn't cause any symptoms. Sometimes, people with the condition don't even know they have a bundle branch block.

For those people who do have signs and symptoms, they may include:

  • Fainting (syncope)
  • Feeling as if you're going to faint (presyncope)
  • Having a slow heart rate (bradycardia)

When to see a doctor

If you've fainted, see your doctor to rule out any serious, underlying causes.

If you have heart disease, or if your doctor has already diagnosed you as having bundle branch block, ask your doctor how often you should have follow-up visits. You might want to carry a medical alert card that identifies you as having bundle branch block in case you're seen in an emergency by a doctor who isn't familiar with your medical history.

Normally, electrical impulses within your heart's muscle signal it to beat (contract). These impulses travel along a pathway, including a slender cluster of cardiac fibers of the heart's electrical system. One area of these fibers is called the bundle of His. This bundle divides into two branches — the right and the left bundles — one for each of your heart's two lower chambers (ventricles).

If one or both of these branch bundles become damaged — due to a heart attack, for example — this change can prevent your heart from beating normally. The heart's electrical impulses that make your heart beat may be slowed down or blocked. When this occurs, your heart's ventricles no longer contract in perfect coordination with one another.

The underlying cause for bundle branch blocks may differ depending on whether the left or right bundle branch is affected. Most cases of left bundle branch block are due to some type of heart disease. Some people with right bundle branch block do not have any other obvious heart problems. Specific causes may include:

Left bundle branch block

  • Heart disease
  • Congestive heart failure
  • Thickened, stiffened or weakened heart muscle (cardiomyopathy)
  • High blood pressure (hypertension)

Right bundle branch block

  • A heart abnormality that's present at birth (congenital) — such as atrial septal defect, a hole in the wall separating the upper chambers of the heart
  • A heart attack (myocardial infarction)
  • A viral or bacterial infection of the heart muscle (myocarditis)
  • High blood pressure (hypertension)
  • Scar tissue that develops after heart surgery
  • A blood clot in the lungs (pulmonary embolism)

The main complication of bundle branch block is a slow heart rate, which can sometimes require a pacemaker. A slow heart rate can occur whether the blockage is on the right or left side of your heart.

People who have a heart attack and develop a bundle branch block have a higher chance of complications, including sudden cardiac death, than do people who have heart attacks and don't develop a bundle branch block. Some people with bundle branch block after a heart attack need a temporary or permanent pacemaker.

Because bundle branch block affects the electrical activity of your heart, it can sometimes complicate the accurate diagnosis of other heart conditions, especially heart attacks, and lead to delays in proper management of those problems.

Some forms of bundle branch block can't be prevented. However, keeping your heart healthy generally helps prevent conditions that increase your risk of bundle branch block, such as coronary artery disease. To reduce your risk of coronary artery diseases that can lead to bundle branch block, you can:

  • Stop smoking if you're a smoker
  • Reduce the dietary cholesterol and fat in your meals
  • Keep your weight at normal levels
  • Exercise regularly, aiming for at least 30 minutes of moderate exercise most days of the week
  • Control any underlying health conditions, such as high blood pressure, high cholesterol and diabetes
© 1998-2015 Mayo Foundation for Medical Education and Research (MFMER). All rights reserved. Terms of use


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