Diseases & Conditions

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Bundle Branch Block

What are the bundle branches?

Normally, your heart beats in a nice, regular fashion. The heartbeat starts in the upper chambers of the heart in an area called the SA node. The impulse then moves to the AV node. The AV node is an area of tissue that carries the impulse through the Bundle of His and then splits into two wire-like branches (the bundle branches). The branches carry the impulse to the Purkinje fibers, which are located in the muscular walls of the ventricles, and cause them to contract.

What is a bundle branch block?

A bundle branch block means the electrical impulses that control the heartbeat cannot move properly throughout the heart. A block in the branches causes the impulses to travel slower than normal.

Diagnosis of bundle branch block

A bundle branch block can be seen on an electrocardiogram (EKG).

Right bundle branch block (RBBB)

Right bundle branch block (RBBB) is very common, and the risk of developing the condition increases with age. Once your doctor sees RBBB on an EKG, the next step is to see if you have underlying heart disease.

If you do not have other heart disease, symptoms of heart disease, or other blocks in your electrical conduction system, no treatment is necessary.

If you have RBBB and another heart condition, such as heart attack or heart failure; dizziness or fainting; or other blocks in your electrical system, you will be treated for the heart disease. You may need a pacemaker if you have symptoms or another heart block.

Left bundle branch block (LBBB)

Left bundle branch block (LBBB) is less common than RBBB. As with RBBB, the risk of developing the condition increases with age. Once your doctor sees LBBB on an EKG, the next step is to see if you have underlying heart disease.

If you do not have other heart disease, symptoms of heart disease, or other blocks in your electrical conduction system, no treatment is necessary.

If you have another heart condition, such as hypertension, coronary artery disease or heart attack, myocarditis or heart failure; dizziness, fainting or chest pain; or another block in your electrical system, you will be treated for the heart disease. You may need a pacemaker if you have another type of heart block or have symptoms of heart block.

How LBBB can affect other cardiovascular tests and conditions

Stress testing and heart attack

Left bundle branch block can make it more difficult to diagnose left ventricular hypertrophy (LVH) and ischemia (decreased blood supply to the heart) during exercise stress testing and during a heart attack.

If you have LBBB, make sure your doctor knows about the condition before you have a stress test. You may need additional testing or a different kind of stress test (done with medicine, not exercise).

You should also carry a copy of your EKG with you.

If you think you are having a heart attack, be sure to tell your doctor or nurse that you have LBBB and give them the copy of the EKG. This will help them see changes in your heart.

If you have signs of LVH, your doctor will use an echocardiogram to diagnose the condition.

References
  1. Gibbons RJ, Balady GJ, Bricker JT, et al. ACC/AHA 2002 guideline update for exercise testing: summary article: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Committee to Update the 1997 Exercise Testing Guidelines). Circulation 2002; 106:1883.
  2. Gibbons RJ, Balady GJ, Beasley JW, et al. ACC/AHA Guidelines for Exercise Testing. A report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Committee on Exercise Testing). J Am Coll Cardiol 1997; 30:260.
  3. Vaduganathan P, He ZX, Raghavan C, et al. Detection of left anterior descending coronary artery stenosis in patients with left bundle branch block: exercise, adenosine or dobutamine imaging? J Am Coll Cardiol 1996; 28:543.

Reviewed: 06/13

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This information is provided by Cleveland Clinic and is not intended to replace the medical advice of your doctor or health care provider. Please consult your health care provider for advice about a specific medical condition.

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