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Arrhythmia And Conduction Disorders: What Is Bundle Branch Block?

by — Last updated: 2020-02-14 in Cardiovascular Disorders and Diseases

When there is interference in the electrical signals that pass through your heart to produce beats, it results in what's called a conduction disorder. Bundle branch block is one of these disorders, where one side of the heart beats slightly faster.

The heart is a complex organ. Even being interrupted for a few seconds can have severe consequences and may require immediate treatment.

Unsurprisingly, numerous conditions and diseases can afflict the heart, many of these falling under arrhythmia. Arrhythmia describes an abnormal heartbeat — either too fast, too slow, or irregular. There are several very dangerous arrhythmias, as well as many symptomless or even natural arrhythmias.

However, some arrhythmias can be warning signs for more severe arrhythmias or dangerous heart diseases. These arrhythmias may cause no symptoms on their own but can alert you to life-threatening conditions or lead to strokes and heart attacks. One example is bundle branch block, which is often harmless on its own.

What is bundle branch block?

When your heart has trouble beating, a pacemaker is often a potential treatment. This device generates electrical signals that get the heart to beat at specified times. The idea for a pacemaker is based on your heart's natural system. Your heart has its own pacemaker, called the sinoatrial node. By producing electrical signals, it gets the top of your heart (the atria) to contract in conjunction with the bottom of your heart (the ventricles). This results in your heart "beating". 

The heart has two atria and two ventricles, both sides having electrical connections to the sinoatrial node. These electrical signals pass from the top to the bottom of your heart, through the so-called "bundle branches". As it happens, the connection between the atria and ventricles can be interrupted on one side or the other. Interrupting the connection causes it to slow down, and one side of the heart contracts a fraction of a second later. This is referred to as bundle branch block.

What symptoms might bundle branch block present with?

Because bundle branch block is so minor, it rarely presents with symptoms. Most of the time, it is found while a doctor is doing tests. Up to five percent of the population may have bundle branch block in the right side of their heart without knowing it.

In those rare cases where bundle branch block is symptomatic, the signs can include lightheadedness, dizziness, lacking energy, or shortness of breath. If these symptoms are not present, the bundle branch block usually isn't an immediate cause for concern.

However, if you have a heart disease, it's important to inform the physician diagnosing you or your doctor. If you have bundle branch block and heart disease, it can increase the risk of mortality from other ailments. In addition, the risk of mortality for heart failure increases when one has bundle branch block.

How does a doctor diagnose bundle branch block?

Bundle branch block is usually found during an ECG. Short for "electrocardiogram", an ECG records the heart's electrical activity. Because so many arrhythmias are caused by some problem within the heart's electrical system, this is a valuable tool. A doctor may conduct this test as part of a routine checkup or while searching for another heart issue. The ECG will show an abnormal pattern in the heart, which will alert the doctor to the presence of bundle branch block.

How is bundle branch block treated?

You may not need treatment, as your heart may be in a good state despite the bundle branch block. A patient with bundle branch block may be worried that it will eventually cause the heart to stop completely. Fortunately, the condition does not work that way, and it very rarely gets worse.

If the symptoms get truly severe, a doctor may recommend a pacemaker. Treatment is also recommended when heart failure has weakened the heart muscle significantly. These patients will have a pacemaker-like device inserted into their heart to stimulate the left ventricle and keep the two sides of the heart beating at a similar rate. This is called cardiac resynchronization.

It would be an understatement to say that bundle branch block is only dangerous when there are symptoms, however. Bundle branch block can be an indicator of underlying disorders, that may require treatment even if the bundle branch block itself does not.

Some of these disorders include chronic lung disease, heart attack, and heart failure (both of which can alter the heart's structure). Blood clots in the lungs, certain infections, or even trauma to the heart or chest can also cause bundle branch block. It is best to treat the underlying sickness rather than the bundle branch block.

Bundle branch blocks on the left side of the heart can be caused by chronic high blood pressure, stretching or thickening of the walls of the heart, or coronary heart disease. These are often related to aging. Because of this, a doctor may do tests to find out if the heart structure is normal, and if so, try to treat high blood pressure where present.

Most patients with bundle branch block will never notice they have it, nor will they require treatment. Where the bundle branch block is either severe or indicative of a more significant underlying problem, more extensive treatment may be needed.

  • Photo courtesy of SteadyHealth