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.

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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).

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.