نظرة عامة
Left bundle branch block (LBBB) is a delay in the pathways in the heart that carry heartbeat signals. It is a type of heart conduction disorder.
Heartbeat signals move through the heart along electrical pathways called bundle branches. The heart has two main bundle branches: one on the right side and one on the left side.
In left bundle branch block, the heart signals on the heart's left side are slowed or blocked. This makes the left lower chamber squeeze later than the lower right one.
The outlook for a person with left bundle branch block varies. The outlook depends on whether there is other heart disease and how well the heart pumps. Many people with left bundle branch block have no symptoms. When symptoms happen, they may include shortness of breath or chest pain. But the condition can be serious. Left bundle branch block is linked to a higher risk of heart failure.
A healthcare professional can look for specific patterns on a heart test called an electrocardiogram to help diagnose LBBB. Treatment depends on the cause of the heartbeat changes. Some people with left bundle branch block need cardiac resynchronization therapy or a heart device called a pacemaker.
Types
Bundle branch block can affect the left or right side of the heart. When it affects the lower left heart chamber, it's called left bundle branch block (LBBB). LBBB is not the same as right bundle branch block (RBBB). RBBB affects the lower right chamber of the heart. This article focuses on left bundle branch block.
There are different types of left bundle branch block (LBBB). The types are grouped based on how much the heart signals are delayed or blocked and how often the changes happen. A healthcare professional can learn the type by looking at the patterns of heart signals on an electrocardiogram.
- Complete left bundle branch block. The heart signals on the left side of the heart are greatly delayed or blocked.
- Incomplete left bundle branch block. Some heart signals are delayed, but some still get through.
- Intermittent or episodic left bundle branch block. The delay or blockage in heart signals happens only sometimes.
- Rate-dependent left bundle branch block. The change in heart signals depends on how fast the heart is beating.
The left bundle branch splits into smaller pathways called fascicles. Other related heart signaling changes can affect these smaller paths. A left anterior or left posterior fascicular block affects one of these pathways. A bifascicular block affects two parts of these pathways.
الأعراض
Many people with left bundle branch block (LBBB) do not have symptoms. The condition may be found when a heart test is done for another reason.
When symptoms occur, they may be related to another heart condition or to another change in the heart's electrical system. Symptoms can include:
- Shortness of breath.
- Trouble exercising.
If other heart signals are affected, you also may have these symptoms:
- Fainting, also called syncope.
- Feeling as if you're going to faint, called presyncope.
A rare condition called painful left bundle branch syndrome can cause chest discomfort that may feel like pain from coronary artery disease. But coronary artery disease is not the cause.
When to seek care
Contact your healthcare professional if you have symptoms of left bundle branch block (LBBB), including:
- Shortness of breath.
- Not being able to exercise as usual.
- Fainting or almost fainting.
Also call if you have been diagnosed with LBBB and your symptoms get worse.
When to seek emergency care
Always call 911 or your local emergency number if you have sudden chest pain that is not explained.
Also get medical help right away if you have:
- Trouble breathing.
- A very fast heartbeat that leads to fainting.
- A very slow heartbeat that leads to unconsciousness.
الأسباب
To understand the cause of left bundle branch block (LBBB), it may help to know how the heart typically beats.
Electrical signals in the heart muscle make the heart beat. These signals move along a pathway. The pathway has two branches, called the right and left bundles. If one or both of these bundles are damaged, the signals can slow down or be blocked. As a result, the heart doesn't beat as it should.
Health conditions that can damage the heart and cause LBBB include:
- A disease of the heart muscle called cardiomyopathy.
- Coronary artery disease.
- Heart attack.
- Heart valve disease.
- High blood pressure.
- Inflammation of the heart muscle, called myocarditis.
- Other changes in the heart's structure, called structural heart disease.
Sometimes, LBBB is found and there is no known structural heart disease.
Some heart procedures or surgeries also may cause heart damage that may lead to LBBB. These include some treatments for aortic valve disease.
عوامل الخطورة
A risk factor is something that makes you more likely to get a health condition. Risk factors for left bundle branch block include:
- Growing older. Bundle branch block is more common in older adults than in younger people.
- Some health conditions. High blood pressure, heart disease, heart valve disease and conditions that change the heart's structure may raise the risk of left bundle branch block.
- Some gene changes. Changes in genes that help the heart's electrical signals move quickly may raise the risk of LBBB. An example is the gene for a protein called connexin 43.
المضاعفات
Possible complications of left bundle branch block (LBBB) include:
- Heart failure. In left bundle branch block, the heart's main pumping chamber may not pump blood as well as it should. The main pumping chamber is the left ventricle. This can cause heart failure or make heart failure worse.
- Cardiomyopathy. In some people, left bundle branch block may cause changes in the size and shape of the lower left heart chamber. This process is called left ventricular remodeling. Over time, this may lead to a type of heart muscle disease called LBBB-induced cardiomyopathy. Some types of cardiomyopathy also may cause LBBB. When it is not clear whether LBBB came before the cardiomyopathy, it may be called LBBB-associated cardiomyopathy.
الوقاية
A healthy lifestyle may help prevent heart conditions that can lead to left bundle branch block (LBBB). Follow these tips to help keep the heart healthy.
- Don't smoke or use other tobacco products. If you smoke or use tobacco, stop. Talk with your healthcare team if you need help.
- Eat healthy foods. Choose whole grains, fruits, vegetables, and lean proteins such as fish and beans. Eat less salt, sugar, and saturated and trans fats.
- Ask about alcohol. Ask your healthcare professional if alcohol is safe for you. Drinking too much alcohol can weaken the heart and make heart failure worse. It also raises the risk of some irregular heartbeats.
- Get regular exercise and stay active. Regular exercise helps the heart work better and keeps blood flowing through the arteries. Try to get at least 150 minutes a week of moderate activity such as walking. Ask your healthcare team what's best for you.
- Keep a healthy weight. Extra body weight can strain the heart. Being overweight raises the risk of high cholesterol, high blood pressure and diabetes. These conditions are all risk factors for heart disease. Ask your healthcare team what a healthy weight is for you.
- Manage blood pressure, cholesterol and blood sugar. Get regular health checkups. Ask your healthcare team how often you need to have your blood pressure, blood sugar and cholesterol levels checked.
- Manage stress. Find ways to reduce emotional stress. Some ideas are to get more exercise, practice mindfulness, listen to music or connect with others in support groups.
- Practice good sleep habits. Poor sleep may raise the risk of heart disease. Adults should try to get 7 to 9 hours of sleep daily. If you have trouble sleeping, talk with your healthcare team about tips that might help.