Bradycardia is an abnormally slow heart rate. In adults, it is defined as a heart rate of less than 60 beats per minute. Different types of bradycardia are collectively referred to as bradyarrhythmias. They include:
- Sinus bradycardia—an unusually slow heartbeat due to heart disease, a reaction to medication, or harmless causes, such as excellent fitness or deep relaxation
- Sick sinus syndrome—an unusually slow heartbeat due to a malfunction of the sinoatrial node, which is the heart's natural pacemaker
- Heart block (atrioventricular block or AV block)—an unusually slow heartbeat due to a slowing or blocking of electrical impulses in the heart’s conduction system
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Bradycardia may be caused by:
Normal responses to:
- Deep relaxation
- Being in excellent physical shape
- The heart’s natural pacemaker developing an abnormal rate or rhythm
- The normal electrical conduction pathway being interrupted
- Another part of the heart taking over as pacemaker
Risk factors that increase your chance of getting bradycardia include:
- Increased age
- Taking certain medications used to treat:
- Exposure to certain toxins
Cardiac disease, such as:
- Electrolyte imbalances
or other collagen vascular diseases
- Head injuries
Infectious diseases, such as:
Some types of bradycardia produce no symptoms. Others may cause noticeable symptoms, such as:
- Fainting or loss of consciousness
- Dizziness or light-headedness
- Mild fatigue
- Irregular heart beat
- Shortness of breath
- Chest pain
Serious forms of bradycardia, such as complete heart block, are medical emergencies. They can lead to loss of consciousness or sudden
The doctor will ask about your symptoms and medical history. A physical exam will be done. Your heart will be examined with a stethoscope.
- Your doctor may need you to have blood tests. These tests will look for problems that may explain the bradycardia.
- Your doctor may need to test your heart function. This can be done with:
Treatment may not be required if you do not have cardiac symptoms and conditions. Your doctor may choose to monitor your heart rate and rhythm instead.
Treatment may include:
- Stopping any medications that slow the heart rate
- Diagnosing and treating any underlying conditions
- Medication to temporarily increase your heart rate
- An artificial pacemaker to establish and maintain a normal heart rhythm
To help prevent bradycardia:
- Treat conditions that might lead to bradycardia.
- Carefully follow your doctor’s directions when using medications, especially those that can cause bradycardia.
- Check with your physician or pharmacist before using any over-the-counter medication or natural supplement. Make sure it does not interact with your other medications.
Follow general advice for preventing heart disease, including:
- Maintain a healthy weight.
- Consult with your doctor about a safe exercise program.
- Avoid smoking.
- Eat a healthy diet that is low in saturated fat and rich in whole grains, fruits, and vegetables.
high blood pressure
American Heart Association
Heart Rhythm Society
National Heart, Lung, and Blood Institute
Canadian Cardiovascular Society
Heart and Stroke Foundation of Canada
Bradycardia. American Heart Association website. Available at:
Updated October 25, 2012. Accessed January 18, 2013.
Fleg J. Arrhythmias and conduction disturbances. In: Beers MH, Berkow R, eds.
The Merck Manual of Geriatrics
[online]. Merck & Co.; 2000:486.
Hurst's The Heart
. 11th ed; 2004.
What is an arrhythmia?
National Heart, Lung and Blood Institute, National Institutes of Health
website. Available at:
Updated July 1, 2011. Accessed January 18, 2013.