Understanding Second-Degree Heart Block

Heart block is a problem with the electrical pathway of the heart. Signals may be too slow. They may not complete their circuit. This can cause sudden changes in your heartbeat.

A normal heart

The electrical activity of the heart starts in the sinoatrial (SA) node in the upper chamber (atrium). It then travels through the atrioventricular (AV) node to reach the lower chamber (ventricle). Along the way, the electrical signal goes to the heart muscles to make the heart pump.

What is heart block?

If you have heart block, the electrical signal is delayed or blocked as it goes through the heart. There are different types of heart block. First-degree heart block is the mildest form and is not really a block. The signals are delayed, but they eventually reach the ventricles. Third-degree heart block is more serious: No signals are able to reach the ventricle. In second-degree heart block, some of the signals reach the ventricles while others do not. There are two types of second-degree heart block:

• Type I second-degree heart block. The electrical signals take longer and longer to move from the upper chambers of the heart to the lower chambers. Finally the signals can no longer reach the ventricles. This causes a missed heartbeat. Then the process starts over again.

• Type II second-degree heart block. Some electrical signals are at times suddenly blocked from passing from the upper chambers to the lower chambers. This may happen in a very regular pattern. It can cause regularly missed heartbeats. This is a more serious condition. It may mean there's more severe damage to the heart's electrical system.

What causes second-degree heart block?

Second-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 problems.

• Inflammatory or infectious heart conditions.

• Other diseases, including rheumatic fever and sarcoidosis.

• Some medicines.

Some babies are born with heart block. It may also run in families.

What are the symptoms of second-degree heart block?

You may not have symptoms. But if you do, they may include:

• Feeling lightheaded or dizzy.

• Fainting.

• Feeling tired.

• Shortness of breath.

• Less ability to exercise.

How is second-degree heart block treated?

Second-degree heart block type I with no symptoms may not need treatment. Your doctor will likely ask you to have regular follow-up visits. You may need to take your own pulse and be alert to changes in your heart rate.

Treatments for second-degree heart block with symptoms include:

• Taking medicines to increase your heart rate in the short-term (acutely) to ease symptoms. This is usually done in the emergency room or hospital.

• Stopping medicines, if they are causing the heart block.

• Getting a pacemaker.

Most people who have type II second-degree heart block will need a pacemaker. This is the case even if they have no symptoms. This is because this type of heart block can often get worse.

What are possible complications of second-degree heart block?

Second-degree heart block may turn into a more serious type of heart block. It may cause a sudden loss of consciousness. Or it may cause the heart to suddenly stop beating.

When should I contact my doctor?

Contact your doctor right away if:

• You feel weak or dizzy.

• You have pain that gets worse.

• Your symptoms don’t get better with treatment, or they get worse.

• You have new symptoms.

Call 911

Call 911 if:

• You are short of breath.

• You have chest pain.

• You faint.