Bundle Branch Blocks. How dangerous are they?

When we sit in a doctor’s office, we tend to hear a lot of medical terminology that we may not understand. This can be especially frightening when we are in the cardiologist’s office.  One of the terms we might hear is “bundle branch block”.

What is a bundle branch block?

  • A bundle branch block is a heart condition wherein there is a delay bundlebranchblockalong the electrical pathway that makes the heart beat.
  • A blockage along this pathway can happen on either the right side or the left side of the heart.
  • These obstacles can make it more difficult for the heart to effectively pump blood through the circulatory system.

What are the causes of a bundle branch block?

The underlying causes for these bundle branch blocks can differ, depending on whether you have one on the right or left side.

Left bundle branch blocks are more often caused by some variation of heart disease:

  • Congestive heart failure
  • Cardiomyopathy (stiffened, thickened, or weakened heart tissue)
  • Hypertension (high blood pressure)
  • Heart disease

Right bundle branch blocks can have a larger range of causes:

  • Congenital defect (an abnormality that is present at birth)
  • Myocardial infarction (heart attack)
  • Myocarditis (bacterial or viral infection of the heart)
  • Hypertension (high blood pressure)
  • Scar tissue due to previous surgeries of the heart
  • Pulmonary embolism (a blood clot located in the lungs)


What are the effects – how dangerous are they?


It can be difficult to give a proper diagnosis with just this one piece of information.  Sometimes your doctor will perform additional tests in order to give them a better picture of what is happening.


  • If there are no other symptoms, the risks of this particular condition are small.
  • It mostly depends on the underlying causes of the block.
  • If the block is caused by a serious heart condition such as a heart attack, that can be more concerning.
  • If the block is caused by a manageable condition such as high blood pressure, then it can be less concerning.
  • Your doctor will keep watch because if you also develop a bundle branch block in the opposite side, he will most likely want to put in a pacemaker in order to regulate the electrical impulses.


When you do hear these frightening terms, remain calm and make sure to get all the information you can from your doctor.  They will help you navigate the management options for your particular situation.

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