HealthSheets™


Understanding First-Degree Heart Block

Cross section of heart showing conduction system.

Heart block is a condition in which the electrical system of the heart does not work properly. Sometimes it can result in a slow heartbeat that is either regular or irregular. This may cause symptoms. There are different types of heart block that can be more or less serious. First-degree heart block is a condition in which the wiring of the heart is slow to send electrical signals but all of the signals are able to pass successfully. There is no electrical block but rather a slowing or delay of the signal. It usually does not cause problems. Often it does not need treatment.

What causes first-degree heart block?

First-degree heart block may be caused by:

  • Natural aging process

  • Damage to the heart from surgery

  • Damage to the heart muscle from a heart attack

  • Other types of heart disease that damage the heart muscle

  • Low thyroid levels

  • Electrolyte abnormalities

  • Inflammatory or infectious heart conditions

  • Other diseases, including rheumatic fever and sarcoidosis

  • Some medicines

In addition, well-conditioned athletes may develop first-degree heart block from heart changes that result from exercising a lot. This is considered normal. Some babies are born with heart block. Heart block may also run in families.

What are the symptoms of first-degree heart block?

First-degree heart block often does not have any symptoms. It may be found when your healthcare provider is examining you for some other reason.

In more severe cases, people may have an uncomfortable awareness of the heartbeat. 

How is first-degree heart block treated?

First-degree heart block usually doesn’t need treatment. Your healthcare provider may ask you to have regular follow-up visits. You may also be asked to take your own pulse and be alert to changes in your heart rate.

What are the  complications of first-degree heart block?

In rare instances, a first-degree heart block may develop into a more serious type of heart block that results in slower heartbeats. This may cause symptoms.

When should I call my healthcare provider?

Call your healthcare provider right away if you have any of these:

  • Unusual tiredness

  • Shortness of breath

  • Chest pain

  • Weakness, dizziness, or fainting

  • Unusual drowsiness or confusion

  • Pain that gets worse

  • Symptoms that don’t get better with treatment, or symptoms that get worse

  • New symptoms

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