The yellow parts of this drawing show the heart's electrical pathways. Normally, electricity travels down these pathways to make the heart beat. With heart block, there is a block in one of these pathways, so electricity cannot travel normally through the heart
**Heart block** is a type of heart disease. The human heart uses electrical signals to make the heart beat. Electricity travels down pathways in the heart to make each part of the heart beat at the right time. 

When a person has a heart block, there is a "block" in one of these electrical pathways. This blocks electricity from travelling normally through the heart. This makes the heart beat more slowly.

In the most serious cases, the heart’s electrical pathways are blocked so badly that electricity cannot travel through the heart. This means the heart’s electrical signals cannot control how the heart beats, or cannot make the heart beat at all.

Symptoms
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Many people with heart block have no symptoms at all.

Other people only have symptoms every once in a while. Sometimes, their heart might skip a beat. This can make the person feel dizzy; faint; or have palpitations (feel their heart pounding).

In the most serious cases of heart block, a person's heart cannot control their heart beats. These cases can be treated with an artificial pacemaker. This is a medical device that is placed into the heart. It sends electrical signals to make the heart beat regularly.

Causes
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Some people are born with heart block. This is called a congenital heart block.

More often, people get heart block later in life. Heart block can be caused by:

* Other types of heart disease, like a heart attack
* Some infections, like diphtheria
* Some medicines, like beta-blockers (a type of medicine for high blood pressure)
* Having open-heart surgery

Types of heart block
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There are three main types of heart block.

### First-degree heart block

This is the least serious type of heart block. It usually causes no symptoms.

### Second-degree heart block

In second-degree heart block, it takes longer and longer for the heart to send electrical signals from the middle of the heart to the ventricles, which pump blood to the body. Eventually, this leads to a skipped heart beat. This can cause dizziness and fainting.

### Third-degree heart block

This is the most serious type of heart block. It is also called a complete heart block. In this type of heart block, no electrical signals reach the heart's ventricles. This means that the electrical signals cannot make the heart pump blood to the body.

Some people with third-degree heart block may have very few symptoms and may not need treatment. However, some people with third-degree heart block have many different symptoms. Third-degree heart block can be a medical emergency. This type of heart block may be treated with a pacemaker.

Diagnosis
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Heart block can be diagnosed with an electrocardiogram (also called an ECG or an EKG). This is a painless test. During the test, pads are placed on a person's chest, arms, and legs. They record the heart's electrical activity.

A cardiologist can help diagnose heart block and order other tests if they are needed.

Related pages
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* Heart
* Heart disease
* Cardiac arrhythmia