Bundle Branch Block- Symptoms, Diagnosis, and Treatment

What Is a Bundle Branch?

A bundle branch is an interruption of the electrical signals inside the ventricles (two lower chambers) of the heart that are needed to complete a heartbeat. This makes it hard for the heart to pump blood and sometimes may lead to serious heart conditions.

The heart has two upper chambers called the atria (singular: atrium), and two lower chambers called the ventricles. The right atrium and ventricle receive oxygen-poor blood, which is pumped to the lungs for oxygenation. The left atrium and ventricle receive oxygenated blood that is pumped to the rest of the body. This two-part pumping action happening in the heart is known as a heartbeat. There are two components to a heartbeat- contraction (systole) and relaxation (diastole). The contraction part of the heartbeat does not happen automatically; it is initiated in the form of electrical impulses by a small mass of highly specialized muscle cells in the top right chamber of the heart, known as the sinoatrial node (SA node). It is the body’s naturally occurring pacemaker.

Similar to the SA node, there is also an atrioventricular node (AV node) located on the intra-atrial septum (a thin wall of tissue that separates the right and left atria of the heart). But unlike the SA node, the AV node cannot generate the impulse, but it transmits them. The muscle fibers in the AV node carry the electrical impulses into the interventricular septum (a tissue that separates the two ventricles), after which they split into two branches- the right bundle branch (RBB) and the left bundle branch (LBB), named after their corresponding ventricles.

What Is a Bundle Branch Block?

A problem (delay or blockage) in the transmission of the electrical signals either by the RBB or the LBB is known as a bundle branch block. There are two types-

Right Bundle Branch Block (RBBB)- Conditions that affect any part of the heart will also cause RBBB. Some of them are-

1. Hyperkalemia- It is a condition where the patient will have too much potassium in their blood. This can cause RBBB leading to delayed electrical impulses.
2. Infections- A couple of examples are infective endocarditis and myocardial infarction, which will directly cause cellular damage to the fibers in the right bundle branch.
3. Pulmonary Embolism or Cor Pulmonale- These conditions increase the intraventricular pressure that will stretch the fibers in the RBB, causing a bundle branch block.
4. Iatrogenic- The term ‘iatrogenic’ refers to a complication that is caused by a medical examination or a treatment. A few iatrogenic procedures that have caused RBBB in the past are right heart catheterization and septal reduction by ethanol ablation (for treating hypertrophic cardiomyopathy).
5. Idiopathic- Although not a common occurrence, Lenegre’s disease and Lev's disease can induce fibrosis and calcification in the fibers of the RBB, leading to a block.
6. Degenerative Heart Conditions- RBBB can occur in patients with degenerative heart diseases like cardiac fibrosis, amyloidosis, aortic valve sclerosis, etc.

Left Bundle Branch Block (LBBB)- Similar to RBBB, any cardiac condition that enlarges the left ventricle of the heart will also cause LBBB. The reason for dilation can be ischemic (heart attack), infective (endocarditis), valvular (stenosis), infiltrative (cardiomyopathy), and inflammatory (myocarditis) medical conditions.

What Are the Symptoms of the Bundle Branch Block?

Most people with a bundle branch block do not have symptoms. Symptoms are more likely to occur if the patient has additional heat conditions. In a few cases, LBBB has been known to aggravate acute chest pain or syncope (fainting) in patients suffering from heart failure.

How Is a Bundle Branch Block Diagnosed?

Different tests that can diagnose a bundle branch block are-

• Electrocardiogram (ECG or EKG)- It is a quick and painless test that measures the electrical activity in the heart. During the procedure, the technician will attach sensors (or electrodes) to the chest that will record the electrical signals in the heart. It can identify the signs and location of the block.

• Echocardiogram- Similar to an ultrasound, an echocardiogram uses sound waves to provide detailed images of the heart and its valves. It will identify the thickness and extent of the structure of the bundle branches.

How Is a Bundle Branch Block Treated?

The bundle branch block itself does not have any treatment, but the clinician will address the underlying heart conditions causing the block. Depending on the severity, the treatment is done either with medication or surgery and sometimes includes both.

1) Medication- It depends on the cause of the block. If it is hypertension, then the clinician will prescribe beta-blockers to reduce blood pressure; if it is infective endocarditis (infection), the prescription will be broad-spectrum antibiotics.

2) Surgery- A few clinicians will suggest a pacemaker, which is a device implanted in the chest to help control the heartbeat. But this treatment is not suitable for everyone; it is recommended if-

• Both RBB and LBB are affected and associated with a heart attack.
• If the block is associated with loss of consciousness.
• In cases of dilated cardiomyopathy.

The process of regularizing the heartbeat in patients with reduced blood flow with the help of a pacemaker is known as cardiac resynchronization therapy or biventricular pacing. A biventricular pacemaker is used in this therapy, and it is different from the other pacemakers by having a third wire connected to the left side of the heart to keep both sides in rhythm.

What Are the Complications of Cardiac Resynchronization Therapy?

As with any surgical procedure, cardiac resynchronization therapy is also associated with its fair share of risks and complications; they are-

• Reaction to anesthesia.

• Swelling or bruising of the upper chest area.

• Bleeding.

• Infection.

• Persistence of heart rhythm problems.

• Displacement of the device wires.

• Mechanical problems with the biventricular pacemaker.

• Pneumothorax (fluid in the lungs).

• Failure of the device.

Conclusion-

Diagnosing a branch bundle block is crucial in preventing future life-threatening heart conditions. If the clinician suspects a block, either symptomatic or asymptomatic, they should refer the patient to a cardiologist for further review. Treatment will improve the quality of life and lifespan of the patient because the focus is on the underlying condition rather than the block itself.