- Filed Under
Dear Dr. Roach: I am a 63-year-old male who, during a routine EKG, showed a left bundle branch block. Can you tell me anything about this diagnosis, what it means, any treatment, future concerns, etc.? I regularly see a vascular cardiologist, and a previous heart attack has been ruled out as the cause. I am a type 2 diabetic and have been treated for high blood pressure since before the EKG. -- M.H.
Dr. Roach: The heart has its own circulatory system as well as nervous system, in addition to its primary job as a muscle. The nervous system serving the heart is composed of specialized tissues that act as the heart's natural pacemaker (called the sinoatrial node), the bundle of His, and the bundle branches. I think of the bundle branches as being like wires that bring the electrical impulse telling the muscle to contract. The left bundle branch has two sub-branches, while the right has one.
A bundle branch block is like a kink in the wire, so the impulse doesn't travel to the left side of the heart through the fast pathway. Instead, the impulse travels cell-to-cell, using the impulses from the right bundle. Fortunately, in a person with a bundle branch block and no symptoms, the risks are small. However, if your right bundle branch gets blocked, that is a problem, and it would be time to get a permanent artificial pacemaker.
A bundle branch block can be caused by poor blood flow to the heart or previous heart attack, so your cardiologist was right to look for that. Often, the condition just occurs in normal hearts as we age, but heart blockages seem to be more common in people with a left bundle branch block, so your cardiologist will keep a careful eye out, especially since diabetes increases your risk as well.
The one other issue with a LBBB is that it becomes difficult to interpret the EKG, so suspected heart disease (blockages of the arteries, the circulatory system of the heart) requires more-sophisticated testing.