The Causes of Left Bundle Branch Block

A left bundle branch block is a condition in the lining of the heart that affects how the heart is able to pump blood to the rest of the body. In most cases, the left bundle branch block is the result of damage that has been occurring to the heart as the result of a different pulmonary condition.


Bundle branch block is an impediment that delays the impulses that make the heart beat. Complications with heart muscle, such as an injury or disease, could slow down the electrical impulses that make the heart beat, or a blockage in the blood vessels surrounding the heart could also have the same effect. The damage occurs to a collection of cardiac material that causes the electrical impulses to the heart known as the bundle of His. This bundle branches off to each of the two heart ventricles. A block on the left ventricle is known as a left bundle branch block. In most cases, bundle branch block itself is not considered critical to be treated as it is more than likely an indication a much more serious heart condition exists.

Heart Conditions

Causes of Left Atrial Enlargement

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Trauma to the heart can bring on bundle branch block, and, in some cases, it can be the result of surgery done to repair the heart. A heart attack can sometimes cause the bundle branch to slow in its electrical impulses; this can happen on both sides or only on the left or right bundle branch block. The scarring that can occur after heart surgery can also put pressure on the bundle branch and slow the electrical impulses from reaching the heart.

Valve Disease

Valve disease can also cause left bundle branch block. The valve can either allow blood to flow backward, which will mean that less blood is getting to the organs that need it. To supply the blood needed in these organs, the heart will pump faster and this will cause the heart to enlarge. This enlarging reduces the flow of blood to the left bundle branch—this can bring on left bundle branch block. The heart valves could also suffer from stenosis, which is a condition that narrows the valves and limits the flow of blood to the organs. Once again, to compensate for that reduced blood flow, the heart must pump harder; this causes the heart to become enlarged, which can lead to left bundle branch block.


What is Mild Cardiomegaly?

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Hypertension, or high blood pressure, is a continuous heart condition that causes the heart to beat harder to produce more blood for the organs; this can lead to left bundle branch block. A person experiencing a continuous heart condition such as hypertension is more likely to get a left bundle branch block. A right bundle branch block is more likely to occur in someone who seems to be in perfect health.


A left bundle branch block could be the result of an infection of the heart muscle known as a myocarditis. This infection could be viral or it could be bacterial. The infection itself slows the heart by affecting the electrical impulses reaching the heart muscle through the left bundle branch.