Heart block


Heart block is a problem in the electrical signals in the heart.

Normally, the heart beat starts in an area in the top chambers of the heart (atria). This area is the heart's pacemaker. The electrical signals travel to the lower chambers of the heart (ventricles). This keeps the heart beat steady and regular.

Heart block occurs when the electrical signal is slowed down or does not reach the bottom chambers of the heart. Your heart may beat slowly, or it may skip beats. Heart block may resolve on its own, or it may be permanent and require treatment.

There are three degrees of heart block. First-degree heart block is the mildest type and third-degree is the most severe.

First-degree heart block:

Second-degree heart block:

Third-degree heart block:


Heart block may be caused by:

You may have heart block because you were born with it. You are more at risk for this if:

Some normal people, will have a first degree block especially at rest or when asleep. This most often occurs in young healthy people.


Talk to your health care provider about your symptoms. The symptoms may be different for first, second, and third-degree heart block.

You may not have any symptoms for first-degree heart block. You may not know you have heart block until it shows up on a test called an electrocardiogram (ECG).

If you have second-degree or third-degree heart block, symptoms may include:

Exams and Tests

Your provider will most likely send you to a heart doctor (cardiologist) to check for or further evaluate heart block.

The cardiologist will talk to you about your medical history and the medicines you are taking. The cardiologist will also:


The treatment for heart block depends on the type of heart block you have and the cause.

If you do not have serious symptoms and have a milder type of heart block, you may need to:

If you have second- or third-degree heart block, you may need a pacemaker to help your heart beat regularly.

Outlook (Prognosis)

With regular monitoring and treatment, you should be able to keep up with most of your usual activities.

Possible Complications

Heart block may increase the risk for:

If you have a pacemaker, you cannot be near strong magnetic fields. You need to let people know that you have a pacemaker.

When to Contact a Medical Professional

Call your provider if you feel:

Call your provider if you have signs of heart failure:

Review Date: 4/14/2019
Reviewed By: Michael A. Chen, MD, PhD, Associate Professor of Medicine, Division of Cardiology, Harborview Medical Center, University of Washington Medical School, Seattle, WA. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.

This information should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed medical professional should be consulted for diagnosis and treatment of any and all medical conditions. Call 911 for all medical emergencies. © 1997- 2007 A.D.A.M., Inc. Any duplication or distribution of the information contained herein is strictly prohibited.