In order for your heart to beat properly, your heart’s tissue conducts electrical impulses throughout your heart muscle in a regular pattern.
This electrical impulse causes the upper chambers (atria) of your heart to contract first, and the two lower chambers (ventricles) to contract right afterwards.
If any part of this electrical pathway is obstructed, it’s known as a bundle branch block. When this happens, the electric impulse moves slower to reach its endpoint. This makes it harder for your heart to pump blood efficiently throughout your body.
With left bundle branch block there is a delay or obstruction along the electrical pathway to your heart’s left ventricle. This is the lower-left portion of your heart.
If the electrical impulse is delayed along the pathway to your heart’s right ventricle, it’s known as right bundle branch block.
Left bundle branch block often doesn’t cause any symptoms. In fact, some people have it for years and never know they have the condition.
For others, however, a delay in the arrival of electrical impulses to the heart’s left ventricle can cause syncope (fainting), due to unusual heart rhythms that affect blood pressure.
Some people might also experience something called presyncope. This involves feeling like you’re about to faint, but never actually fainting.
Other symptoms can include fatigue and shortness of breath.
Left bundle branch block can be caused by several different heart conditions.
For example, a heart attack can damage your heart tissue, making it harder for your heart to conduct electrical impulses. This can result in bundle branch block at either the right or left ventricle. A new left bundle branch block should warrant work-up for a prior heart attack.
Other conditions that can cause a left bundle branch block include:
- coronary artery disease
- heart failure
- high blood pressure (hypertension)
- problems with the aortic valve
- heart infection (myocarditis)
- weakened, enlarged, or stiffened heart muscle (cardiomyopathy)
Sometimes, however, left bundle branch block can happen without any underlying heart condition. It’s not known why this happens, but it’s most often seen in older adults.
Doctors usually diagnose left bundle branch block by using the following tests:
- An electrocardiogram (EKG or ECG). This is the test that’s most often used to diagnose an issue with your heart’s electrical impulses. An electrocardiogram is a painless test that involves placing stickers (called leads) around your chest. The leads conduct electricity. They’re connected to wires that sense the electrical impulses of your heart and monitor your heart’s rhythm.
- An echocardiogram. An echocardiogram uses sound waves to produce live images of your heart. It allows your doctor to see how your heart and your heart valves are working and how the chambers are pumping. It also lets your doctor measure the thickness of your heart muscle and to see the overall structure of your heart. This test can be helpful for identifying possible causes of left bundle branch block.
- A pharmacologic stress test. This test uses medicine to make your heart work just as it does when you exercise, without requiring you to exert yourself. It dilates the blood vessels leading to your heart, but it doesn’t increase your heart rate. This test helps your doctor determine if there’s adequate blood flowing to your heart when you exert yourself versus when you’re at rest.
- Blood work. Your doctor may order blood work to check your cholesterol levels and other factors that could be contributing to your left bundle branch block.
Left bundle branch block doesn’t always require treatment, especially if you don’t have any underlying heart conditions.
If you do have another heart condition, your doctor might suggest treating the underlying cause or no treatment at all if you’re stable.
If you have left bundle branch block due to electrical problems with your conduction system, for example, you may need a pacemaker. This is a device that emits electricity to help your heart maintain a consistent rhythm.
If you have high blood pressure, you may need to take medication to keep it under control. This will also help reduce the strain on your heart.
While treating the underlying condition might not completely get rid of left bundle branch block, it can lessen the risk of complications, such as progressive disease.
While anyone can develop left bundle branch block, some people have a higher risk due to other conditions that affect their heart or lungs.
Conditions that can increase your risk of bundle branch block on either the left or right side include:
If you have any of these conditions, your doctor may regularly monitor your heart rhythm to detect any signs of bundle branch block.
A disrupted electrical signal in your heart can cause the following complications:
- abnormal heart rhythms
- slower heart rate
- increased risk of heart failure
Sometimes, a bundle branch block can make it harder for doctors to diagnose other heart conditions, such as heart failure or enlargement.
If you’ve been diagnosed with left bundle branch block, make sure to tell any other doctors you see that you have this condition.
If you have left bundle branch block, it’s important that you have regular medical checkups, so your doctor can monitor your heart health and prescribe treatment if it becomes more serious.
For the best outcomes it’s vital to follow your doctor’s instructions and to get the follow-up care you need.
Left bundle branch block is a condition in which there’s a slowing along the electrical pathway to your heart’s left ventricle. When this happens, the electric impulse has to travel further to reach its endpoint. This makes it harder for your heart to pump blood efficiently.
Left bundle branch block can be caused by many heart conditions, and it’s typically diagnosed with an electrocardiogram or an echocardiogram.
Depending on the severity of your left bundle branch block, your doctor may recommend a pacemaker or medications to help treat the underlying condition that could be causing a problem with the electrical pathway in your heart.