Definition

Bundle branch block is a condition where there is a delay or blockage in the pathways that transmit electrical signals responsible for making your heart beat. Under normal conditions, your heart beats with a steady rhythm. The heartbeat starts in the upper chambers of the heart in an area called the SA node and then spreads to all heart chambers. The electrical signal passes through two branches, called the bundle branches. From there, the electrical signal is carried to the Purkinje fibers located in the heart muscle walls, causing the heart to contract.

A blockage or delay in the transmission of impulses through the bundle branches is known as a bundle branch block. This condition can sometimes make it harder for your heart to efficiently pump blood throughout your body. Based on the structure of the bundle branches, there are two types of bundle branch blocks depending on the affected branch:

• Right Bundle Branch Block (RBBB)
• Left Bundle Branch Block (LBBB)

Causes

Normally, electrical signals in the heart muscle cause the heart to beat (contract). These impulses travel through the heart’s electrical pathways, including two branches: the right bundle branch and the left bundle branch. If one or both of these branches are damaged, such as after a heart attack, the electrical impulses may be blocked, causing the heart’s rhythm to become abnormal.

The causes of bundle branch blocks depend on the affected branch. Sometimes, the cause is unknown. Some known causes include:

• Left Bundle Branch Block (LBBB):
• Heart attack (myocardial infarction)
• High blood pressure (hypertension)
• Inflammation of the heart muscle (myocarditis)
• Thickening, stiffening, or weakening of the heart muscle (cardiomyopathy)
• Right Bundle Branch Block (RBBB):
• Blood clots in the lungs (pulmonary embolism)
• Heart attack (myocardial infarction)
• Congenital heart defects, such as a hole in the wall separating the heart chambers (atrial septal defect)
• High blood pressure in the pulmonary arteries (pulmonary hypertension)
• Inflammation of the heart muscle (myocarditis)

Risk Factor

Factors that increase the risk of developing bundle branch blocks include:

• Aging: Bundle branch block is more common in older adults than in younger individuals.
• Underlying health conditions: Conditions such as high blood pressure or heart disease increase your risk of bundle branch block.

Symptoms

In most cases, bundle branch block does not cause symptoms. Some people with this condition may not even know they have it. In rare cases, symptoms may include fainting (syncope), which occurs due to abnormal heart rhythms affecting blood pressure.

Bundle branch block often doesn’t cause any symptoms, but if it is detected, it may indicate a more serious underlying heart condition. For example, an issue with the transmission of electrical signals in the heart may suggest that part of the heart is not receiving enough blood supply, affecting the delivery of oxygen to tissues. Research also shows that people with left bundle branch block may be at a higher risk of heart disease than those without it.

Diagnosis

To diagnose bundle branch block, your doctor will begin by asking about your symptoms and medical history, including any heart disease or other conditions that you or your family may have. A physical exam, especially listening to your heart with a stethoscope, will also be performed. However, diagnosing bundle branch block is often difficult based on just the interview and physical exam. Additional tests are usually needed to confirm the diagnosis.

Some of the tests your doctor may use include:

1. Electrocardiogram (ECG or EKG):
This test records the electrical impulses in your heart using wires attached to your chest and limbs. It can show signs of bundle branch block and indicate whether the right or left bundle branch is affected. An EKG is a fundamental test for diagnosing bundle branch block.

2. Echocardiogram:
This test uses sound waves to provide detailed images of the heart’s structure and muscle thickness. It can also show whether your heart valves are functioning normally. Your doctor may use this test to determine the condition causing the bundle branch block.

Management

Most cases of bundle branch block do not cause symptoms and do not require treatment. If you do not have heart disease, heart disease symptoms, or other electrical issues in the heart, you may not need therapy. However, treatment may be considered if you have:

• A history of heart attack or heart failure
• A history of fainting
• Chest pain

Treatment options for bundle branch block include:

1. Medications:
If you have a heart condition causing bundle branch block, treatment may involve medications to lower high blood pressure or relieve heart failure symptoms.

2. Surgery and Other Procedures:
If you have bundle branch block and a history of fainting, your doctor may recommend a pacemaker. A pacemaker is a device implanted under the skin of your upper chest with two wires connected to the right side of your heart. The pacemaker sends electrical impulses when needed to help your heart beat regularly.
If you have bundle branch block with poor heart pumping function, you may need cardiac resynchronization therapy (biventricular pacing). This procedure is similar to pacemaker implantation, but you will have a third wire connected to the left side of your heart to keep both sides of your heart in rhythm. This therapy helps the two lower chambers of your heart contract simultaneously.

Complications

If both the right and left branches are blocked, a complete blockage of electrical signals from the upper to the lower chambers of the heart can occur. This lack of electrical signals can slow your heart rate, cause fainting and irregular heart rhythms, and lead to serious complications.

Bundle branch block can also affect the heart’s electrical activity, making it difficult to diagnose other heart conditions, such as heart attacks, and may delay proper management of these issues.

Prevention

There is no known way to prevent bundle branch blocks. However, you can reduce your risk by properly managing and treating heart disease or other conditions that may cause bundle branch block.

When to See a Doctor?

If you’ve experienced fainting, consult your doctor to rule out serious causes. If you have a history of heart disease or have been diagnosed with bundle branch block, talk to your doctor about treatment options and how often you should have check-ups.

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