What is bradycardia?

Having bradycardia (say "bray-dee-KAR-dee-uh") means your heart beats very slowly. For most people, a heart rate of 60 to 100 beats a minute while at rest is considered normal. If your heart beats less than 60 times a minute, your doctor may diagnose bradycardia.

A slow heart rate is sometimes normal and can be a sign of being very fit. Healthy young adults and athletes often have heart rates of less than 60 beats a minute.

In other people, bradycardia is a sign of a problem with the heart’s electrical system. It means that the heart's natural pacemaker is not working right or that the electrical pathways of the heart are disrupted. In severe forms of bradycardia, the heart beats so slowly that it does not pump enough blood to meet the body's needs. This can be life-threatening.

What causes bradycardia?

Bradycardia can be caused by:

• Changes in the heart that are the result of aging.
• Diseases that damage the heart's electrical system. These include coronary artery disease, heart attack, and infections such as endocarditis and myocarditis.
• Conditions that can slow electrical impulses through the heart. Examples include having a low thyroid level (hypothyroidism) or an electrolyte imbalance, such as too much potassium in the blood.
• Some medicines for treating heart problems or high blood pressure, such as beta-blockers, antiarrhythmics, and digoxin.

What are the symptoms?

A very slow heart rate may cause you to:

• Feel dizzy or lightheaded.
• Feel short of breath and find it harder to exercise.
• Feel tired.
• Have chest pain or a feeling that your heart is pounding or fluttering (palpitations).
• Feel confused or have trouble concentrating.
• Faint, if a slow heart rate causes a drop in blood pressure.

Some people don't have symptoms, or their symptoms are so mild that they think they are just part of getting older.

You can find out how fast your heart is beating by taking your pulse. If your heartbeat is slow or uneven, talk to your doctor.

How is bradycardia diagnosed?

Your doctor may be able to diagnose bradycardia by doing a physical exam, asking questions about your past health, and doing an electrocardiogram (EKG or ECG). An EKG measures the electrical signals that control heart rhythm, so it is the best test for bradycardia.

But bradycardia often comes and goes, so a standard EKG done in the doctor’s office may not find it. An EKG can identify bradycardia only if you are actually having it during the test.

You may need to use a portable (ambulatory) electrocardiogram. This lightweight device is also called a Holter monitor or a cardiac event monitor. You wear the monitor for a day or more, and it records your heart rhythm while you go about your daily routine.