Bundle Branch Block

What Is Bundle Branch Block?

Bundle branch block (BBB) is a blockage or disruption along the pathway that sends electrical impulses to the bottom chambers (ventricles) of the heart to make them contract. This pathway includes two branches: the left bundle and right bundle. If one bundle is damaged, the ventricles rely on the other bundle to receive and respond to signals coming from the heart’s upper right chambers. The blockage causes an irregular heartbeat.

BBB often doesn’t cause symptoms, and many people don’t require treatment unless they have an underlying heart condition or conditions. If both bundles are blocked, the heart may beat very slowly and require a pacemaker.

Bundle Branch Block Symptoms

When BBB causes symptoms, they may include:

• Dizziness
• Fainting (syncope)
• Feeling like you might faint (presyncope)

With BBB, you’re much more likely to experience symptoms if you have an underlying heart condition or if your BBB is severe and on both sides of the heart. People with both right and left BBB may have the following symptoms:

• Abnormal heartbeat rhythm (arrhythmia)
• Shortness of breath (dyspnea)
• Slow heart rate (bradycardia)

What Causes Bundle Branch Block?

Depending on whether the left or the right bundle branch is affected, the cause for BBB can differ. In some people, the cause is unknown.

Causes for left bundle branch block can include:

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

Causes for right bundle branch block can include:

• Blood clot in the lungs (pulmonary embolism)
• Heart attack (myocardial infarction)
• Heart structure problems that are present at birth (congenital heart defects), including a hole in the wall that divides the heart’s upper chambers (called an atrial septal defect).
• High blood pressure in the pulmonary arteries (pulmonary hypertension).
• Inflammation of the heart muscle (myocarditis).

Bundle Branch Block Diagnosis

BBB is mainly diagnosed using two tests:

• Electrocardiogram (ECG or EKG): a diagnostic tool that records your heart’s electrical activity on a graph. An ECG can detect slow, fast or otherwise abnormal heart rhythms.
• Echocardiogram (echo): This test uses sound waves to create a moving picture of your heart. In addition to showing the structure of the heart and its valves, an echo can reveal areas of poor blood flow in the heart.

If you’re diagnosed with BBB, your healthcare provider will check you for related health conditions and may order other tests.

Bundle Branch Block Treatment

The majority of people with BBB don’t have symptoms and don't need to be treated. For those who need treatment, there are medications, implantable devices and other options.

Medication

If a heart condition causes your BBB, treatment might involve medications that lower high blood pressure or reduce heart failure symptoms.

Other Treatment Options

If you have BBB and a history of fainting, your doctor might recommend a pacemaker. Implanted beneath the skin near the collarbone through a minor procedure, a pacemaker releases electrical impulses to stimulate the heart to maintain a regular heartbeat. Two wires connect the device to the right side of the heart.

If you have BBB and low heart-pumping function, your doctor may recommend cardiac resynchronization therapy (CRT). CRT helps the heart's chambers contract in a more organized, efficient manner. Similar to pacemaker implantation, CRT requires a third wire to be connected to the left side of your heart so that the CRT device can keep both sides in a normal rhythm.