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Bundle Branch Block


Disease: Bundle Branch Block Bundle Branch Block
Category: Cardiovascular diseases
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Disease Definition:

When there’s a delay or obstruction along the pathway that electrical impulses travel to make the heart beat, bundle branch block occurs, which is usually a sign of another underlying heart problem and develops in people who appear healthy.

The electrical impulses that make the heart beat could be slowed or blocked due to injury or damage to the heart muscle or blockage of a blood vessel in the heart. This interference could cause bundle branch block despite the fact that it lasts for only a fraction of a second. Sometimes, it could be difficult for the heart to pump blood forcefully and efficiently through the circulatory system because of bundle branch block.

A person will need treatment of any underlying health conditions that could cause bundle branch block, such as coronary heart disease, despite the fact that bundle branch block itself doesn’t require any direct treatment.

Work Group:

Prepared by: Scientific Section

Symptoms, Causes


Although in some cases this condition doesn’t cause any signs or symptoms, in other cases it may cause:


  • Dizziness
  • A slow heart rate (brachycardia)
  • Fainting (syncope)
  • Presycope, which is when a person feels that he/she is going to faint.

In some cases, this condition could be congenital, and a person could have it for years without knowing it. When bundle branch block occurs on the left side of the heart, it will be more serious than when it occurs on the right side of the heart.


The electrical impulses within the heart’s muscle that signal it to contract (beat) travel along a pathway that passes from the heart’s upper chambers (atria) through a small mass of cells that are called the AV (atrioventricular) node and then to the lower chambers (ventricles).
These impulses move along a slender cluster of cardiac fibers called the “bundle of His” along the route on this pathway. This bundle of His divides into two branches; the right and the left bundles, one for each of the heart’s ventricles.

In case one or both of these branch bundles become damaged as a result of a heart attack, a person's heart can be prevented from beating normally because of this change.
The ventricles don’t contract in perfect coordination with one another when the heart’s electrical impulses that make the heart beat become blocked or slowed down.

Some of the causes of this condition could be:


  • A bacterial or viral infection of the heart muscle (myocarditis)
  • A heart attack (myocardial infarction)
  • High blood pressure (hypertension)
  • Stiffened, thickened or weakened heart muscle (cardiomyopathy)
  • A congenital heart abnormality, including an atrial septal defect, which is a hole in the wall separating the upper chambers of the heart
  • Scar tissue that develops after heart surgery.



Although complications are more common in people who have a left side bundle branch block, the complications are usually the same whether the blockage is on the right or left side of the heart.

These complications include heart arrhythmia, cardiac arrest or sudden cardiac death and a slow heart rate.

People who have had heart attack but don’t have bundle branch block have a lower chance of complications and death, than those that have heart attacks and develop bundle branch block.

Bundle branch block could sometimes complicate the accurate diagnosis of other heart complications, such as heart attacks, and lead to delays in proper management of those problems because it affects the electrical activity of the heart.


Although the underlying heart condition that caused the bundle branch block should be treated, most people with this condition don’t need any treatment because they don’t have any symptoms.

Medications could be used in order to reduce high blood pressure or lessen the effects of heart failure.
Reperfusion therapy is recommended especially for people with left bundle branch block who have had a heart attack.
In this treatment, in order to dissolve blood clots and increase the flow of blood to the heart, medications called streptokinase or tissue plasminogen activators are used. The patient should talk to the doctor in case they're concerned about taking these medications, because they carry a high risk of bleeding. Reperfusion therapy is usually given in the emergency situation.

Implanting an artificial pacemaker could be recommended for some people with bundle branch block and a history of fainting. This device weighs as little as an ounce and is as tiny as a quarter. It is a compact battery-operated device that can be implanted under the skin (internal pacemaker).
During one or two hour surgery performed under local anesthesia; the internal pacemaker is placed near the collarbone. In order to keep the heart beating regularly, this device provides electrical pulses. It also has sensors that detect whenever the heart needs a signal from the pacemaker in order to normalize the heart rate.
Pacemakers usually last for many years before the battery needs to be changed. However, in order to keep the device working properly and reduce the risks associated with their use, the patient should talk to the doctor.


Another option to increase blood flow to the heart is to perform coronary angioplasty. Angioplasty opens blocked coronary arteries, letting blood flow more freely to the heart. In this procedure, doctors insert a long, thin tube (catheter) that's passed through an artery, usually in the leg, to a blocked artery in the heart. This catheter is equipped with a special balloon tip. Once in position, the balloon tip is briefly inflated to open up a blocked heart artery. At the same time, a metal mesh stent may be inserted into the artery to keep it open long term, restoring blood flow to the heart. Depending on the patient condition, the doctor may opt to place a stent coated with a slow-releasing medication to help keeping the artery open.


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