Overview

Bundle branch block is a condition in which there's a delay or blockage along the pathway that electrical impulses travel to make your heart beat. It sometimes makes it harder for your heart to pump blood efficiently through your body.

The delay or blockage can occur on the pathway that sends electrical impulses either to the left or the right side of the bottom chambers (ventricles) of your heart.

Bundle branch block might not need treatment. When it does, treatment involves managing the health condition, such as heart disease, that caused bundle branch block.

Symptoms

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

Signs and symptoms in people who have them might include:

  • Fainting (syncope)
  • Feeling as if you're going to faint (presyncope)

When to see a doctor

If you've fainted, see your doctor to rule out serious 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 a doctor who isn't familiar with your medical history sees you in an emergency.

Causes

Normally, electrical impulses within your heart's muscle signal it to beat (contract). These impulses travel along a pathway, including the right and the left bundles. If one or both of these branch bundles become damaged — due to a heart attack, for example — this can block the electrical impulses and cause your heart to beat abnormally.

The cause for bundle branch blocks can differ depending on whether the left or right bundle branch is affected. It's also possible that this condition can occur without a known cause.

Causes can include:

Left bundle branch block

  • Heart attacks (myocardial infarction)
  • Thickened, stiffened or weakened heart muscle (cardiomyopathy)
  • A viral or bacterial infection of the heart muscle (myocarditis)
  • 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 in the pulmonary arteries (pulmonary hypertension)
  • A blood clot in the lungs (pulmonary embolism)

Risk factors

Risk factors for bundle branch block include:

  • Increasing age. Bundle branch block is more common in older adults than in younger people.
  • Underlying health problems. Having high blood pressure or heart disease increases your risk of having bundle branch block.

Complications

The main complication of bundle branch block, right or left, is to progress to a complete block of the electric conduction from the upper chambers of the heart to the lower. This can slow your heart rate, which can cause fainting and lead to serious complications and abnormal heart rhythms.

People who have a heart attack and develop a left bundle branch block have a higher chance of complications, including sudden cardiac death, than do people who don't develop the condition after a heart attack.

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.

May 15, 2018
References
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  3. Sauer WH. Right bundle branch block. https://www.uptodate.com/contents/search. Accessed Feb. 11, 2018.
  4. Bundle branch block and fascicular block. Merck Manual Professional Version. https://www.merckmanuals.com/professional/cardiovascular-disorders/arrhythmias-and-conduction-disorders/bundle-branch-block-and-fascicular-block. Accessed Feb. 11, 2018.
  5. Cardiac resynchronization therapy. American Heart Association. http://www.heart.org/HEARTORG/Conditions/HeartFailure/Cardiac-Resynchronization-Therapy_UCM_452920_Article.jsp. Accessed Feb. 11, 2018.
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