Heart Block

Overview

What is heart block?

Heart block is a problem with the heart's electrical system that causes your heart to beat too slowly (bradycardia). The condition is also called atrioventricular (AV) block. The AV node is a cluster of cells that connects the electrical activity in the top chambers of the heart (atria) to the bottom chambers of the heart (ventricles). If you have heart block, the electrical signal from the AV node to the ventricles that controls your heartbeat is partly or completely blocked from reaching the ventricles.

What are the types of heart block?

Heart block can be first, second or third degree, depending on the extent of electrical signal impairment.

First-degree heart block: The electrical impulse still reaches the ventricles, but moves more slowly than normal through the AV node.

Second-degree heart block is classified into two categories: Type I and Type II.

Type I, also called Mobitz Type I or Wenckebach’s AV block): The less serious form of second-degree heart block. The electrical signal gets slower and slower until your heart actually skips a beat.

Type II, also called Mobitz Type II: Some of the electrical signals do not reach the ventricles, and the pattern is irregular. Your heartbeat may be slower than normal.

Third-degree heart block: The electrical signal from the atria to the ventricles is completely blocked. To make up for this, a section of the ventricles acts like a pacemaker to create electrical signals. The signals keep the heart pumping blood, but at a much slower rate than normal.

Who is at risk of having heart block?

Heart block can be present at birth (congenital), but that is not usually the case. Your risk of having heart block gets greater as you age and is higher if you have heart disease.

First-degree heart block is common among well-trained athletes, teenagers, young adults, and people with a highly active vagus nerve.

Symptoms and Causes

What causes heart block?

The most common cause of heart block is heart attack. Other causes include heart disease, problems with the heart’s structure and rheumatic fever. Heart block can also be caused by damage to the heart during open heart surgery, as a side effect of some medications or exposure to toxins.

What are the symptoms of heart block?

First-degree heart block often does not cause symptoms. It may be found during a routine electrocardiogram (ECG). The heart rate and rhythm are usually normal.

Symptoms of second- and third-degree heart block include fainting, chest pain and feeling dizzy, tired or short of breath. Symptoms of third-degree heart block, the are more intense due to the slow heart rate. If you have severe symptoms get medical attention right away.

How is heart block diagnosed?

Electrophysiologists are doctors who specialize in the electrical activity of the heart. Your primary doctor or cardiologist may refer you to an electrophysiologist to find out if you have heart block.

An evaluation includes an exam, review of your health history and medications, and tests.

An ECG records your heart’s electrical activity and shows problems with your heart. This is a useful test to check for heart block. You may need to wear an ambulatory monitor for 24 to 48 hours so the doctor can collect more information about your heart’s electrical activity. Common devices are a Holter monitor and event recorder. If you need to use a monitor, you will get detailed information about how to use it.

An electrophysiology study can also help diagnose heart block. This involves inserting a long, thin tube called a catheter through a blood vessel and guiding it to the outside of your heart. The test allows your doctor to map your heart’s electrical activity and find any problems. If you need this test, you will get more detailed information.

Diagnosis and Tests

How is heart block diagnosed?

If your primary care physician suspects that you have heart block, he or she probably will refer you to a cardiologist for a complete cardiac evaluation. At the Sydell and Arnold Miller Family Heart, Vascular & Thoracic Institute, our cardiologists will start by obtaining your medical records from your primary care physician, including records of any heart tests you have had done.

Your cardiologist will review your complete medical history with you and ask you questions about your overall health, your diet and activity level, and your family medical history. The cardiologist also will want to know about any medications you are taking (prescription or over the counter) and whether you smoke or use drugs.

You will undergo a complete physical exam during which the doctor will listen to your heart and check your pulse to measure your heart rhythm and heart rate. He or she will check you for signs of heart failure, such as fluid retention in the legs and feet.

An ECG is a useful test to diagnose heart block. An ECG records the heart’s electrical activity. The test produces a graph that shows the heart rate and rhythm and the timing of the electrical signals as they move through the heart.

Cardiologists can look at the graph created during an ECG and determine whether a patient has heart block and how severe it is, based on the patterns of the heartbeat, rhythm and signal timing.

Your cardiologist may want to record your heart’s electrical signals over a longer period of time. If so, you will be asked to wear a portable ECG. A Holter monitor is a type of portable ECG that is worn for 24 to 48 hours. The Holter monitor continuously records the heart’s electrical activity. An event monitor is another type of portable ECG that is worn for a longer period of time and records the heart’s electrical activity at specified times, rather than continuously.

An electrophysiology study is another useful tool to help diagnose heart block. This minimally invasive test uses thin, flexible wires (catheters) that are placed onto the heart’s surface to record the heart’s electrical activity. The Miller Family Heart, Vascular & Thoracic Institute includes some of the world’s leading experts in electrophysiology who are highly skilled at creating “maps” of the heart’s electrical activity using electrophysiology studies for the most accurate diagnosis and treatment.

Management and Treatment

What treatments are available for patients with heart block?

Treatment for heart block treated depends on what is causing it, how bad it is and the symptoms it causes. Sometimes, making changes to medications or treatment for heart disease stops heart block.

If you have first-degree heart block, you probably won’t need treatment.

If you have second-degree heart block and have symptoms, you may need a pacemaker to keep your heart beating like it should. A pacemaker is small device that sends electrical pulses impulses to your heart.

Third degree heart block is often first discovered during an emergency situation. Treatment almost always includes a pacemaker.

If you need a pacemaker, your cardiologist/electrophysiologist will talk to you about the details, the type that is best for you and what to expect before, during and after you get your pacemaker.

Prevention

Who is at risk for heart block?

Heart block can be present at birth (congenital), but most heart block develops after birth. In general, the risk of acquired heart block increases with age, along with the incidence of heart disease.

First-degree heart block is common among well-trained athletes, teenagers, young adults, and people with a highly active vagus nerve. People with a variety of heart disease, including coronary artery disease, rheumatic heart disease, sarcoidosis or other structural heart disorders, are also at risk for developing first-degree heart block.

Outlook / Prognosis

How does heart block affect my life?

If you have first-degree heart block, ask your cardiologist/electrophysiologist if you need to make any changes to your lifestyle or medications. This type of heart block does not usually get in the way of your normal activities.

If you have second-degree or third-degree heart block, your doctor about the types of activity and diet that are best for you. If you get a pacemaker, you may need to limit some activities and you will need regular checks to make sure that your pacemaker is working like it should.

Living With

If you have a pacemaker for second- or third-degree heart block, your cardiologist may recommend some restrictions about the types of exercise you can participate in (such as contact sports), but in general, a pacemaker will not seriously restrict your ability to take part in sports and leisure activities.

Your cardiologist will want to periodically check your pacemaker to make sure that it continues to meet your needs. Many Cleveland Clinic patients who have pacemakers use a special monitoring system that allows them to use a phone to send information from their pacemaker to their doctor’s office. It is important to follow your doctor’s instructions for pacemaker monitoring so he or she can ensure your pacemaker is correctly regulating your heartbeat.

If you have a pacemaker, you should avoid close contact with magnetic devices and any device that sends out an electrical field. When traveling, tell airport security screeners that you have a pacemaker, and carry a card that states the type of pacemaker you have. It is important to tell all of your doctors, your dentist and other healthcare providers that you have a pacemaker. Some medical procedures, such as magnetic resonance imaging (MRI), can interfere with pacemakers.

Resources

To learn more about heart block, contact us or call the Miller Family Heart, Vascular & Thoracic Institute Resource & Information Nurse at 216.445.9288 or toll-free at 800.289.6911. We would be happy to assist you.

Doctors vary in quality due to differences in training and experience; hospitals differ in the number of services available. The more complex your medical problem, the greater these differences in quality become and the more they matter.

Clearly, the doctor and hospital that you choose for complex, specialized medical care will have a direct impact on how well you do. To help you make this choice, please review our Miller Family Heart, Vascular & Thoracic Institute Outcomes.

Cleveland Clinic Heart, Vascular & Thoracic Institute Cardiologists and Surgeons

Choosing a doctor to treat your abnormal heart rhythm depends on where you are in your diagnosis and treatment. The following Heart, Vascular & Thoracic Institute Sections and Departments treat patients with Arrhythmias:

The Heart, Vascular & Thoracic Institute has specialized centers to treat certain populations of patients:

Learn more about experts who specialize in the diagnosis and treatment of arrhythmias.

For younger patients with abnormal heart rhythms:

See About Us to learn more about the Sydell and Arnold Miller Family Heart, Vascular & Thoracic Institute.

Contact

If you need more information, click here to contact us, chat online with a nurse or call the Miller Family Heart, Vascular & Thoracic Institute Resource & Information Nurse at 216.445.9288 or toll-free at 866.289.6911. We would be happy to help you.

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Last reviewed by a Cleveland Clinic medical professional on 07/18/2019.

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Cleveland Clinic is a non-profit academic medical center. Advertising on our site helps support our mission. We do not endorse non-Cleveland Clinic products or services. Policy

Cleveland Clinic is a non-profit academic medical center. Advertising on our site helps support our mission. We do not endorse non-Cleveland Clinic products or services. Policy