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 underlying 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 bundle branch block.

Rarely, signs and symptoms may include fainting (syncope) or 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 have been diagnosed with bundle branch block, ask your doctor how often you should have follow-up visits.

Causes

Normally, electrical impulses within the heart muscle cause it to beat (contract). These impulses travel along a pathway, including two branches called the right and the left bundles. If one or both of these branch bundles are damaged — due to a heart attack, for example —the electrical impulses can become blocked, and your heart will beat abnormally.

The cause for bundle branch blocks can differ depending on whether the left or the right bundle branch is affected. Sometimes, there is no known cause.

Causes can include:

Left bundle branch block

  • Heart attack (myocardial infarction)
  • High blood pressure (hypertension)
  • Infection of the heart muscle by bacteria or virus (myocarditis)
  • Thickened, stiffened or weakened heart muscle (cardiomyopathy)

Right bundle branch block

  • Blood clot in the lungs (pulmonary embolism)
  • Heart attack (myocardial infarction)
  • Heart defects that are present at birth (congenital) — such as a hole in the wall separating the upper chambers of the heart (atrial septal defect)
  • High blood pressure in the pulmonary arteries (pulmonary hypertension)
  • Infection of the heart muscle by bacteria or virus (myocarditis)

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

If both the right and the left bundles are blocked, the main complication is a complete blockage of the electric signaling from the upper to the lower chambers of the heart. The lack of signaling can slow your heart rate, leading to fainting, abnormal heart rhythms and other serious complications.

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.

Oct. 15, 2020
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