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Pronounced: Bray-dee-car-dee-uh


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

Heartbeat: Anatomy of the Heart

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Causes  ^

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  ^

Factors that may increase your chance of bradycardia include:

Symptoms  ^

Some types of bradycardia produce no symptoms. Others may cause noticeable symptoms, such as:

  • Fainting or loss of consciousness
  • Lightheadedness
  • Weakness
  • 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 cardiac arrest.

Diagnosis  ^

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  ^

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

Prevention  ^

To help reduce your chance of bradycardia:

  • Treat any health 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.
    • Treat your high blood pressure and/or diabetes.
    • Treat your high cholesterol or triglycerides.

American Heart Association

Heart Rhythm Society


Canadian Cardiovascular Society

Heart and Stroke Foundation


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.

Explore arrhythmia. National Heart, Lung and Blood Institute, National Institutes of Health website. Available at: Updated July 1, 2011. Accessed January 18, 2013.

Last reviewed December 2014 by Michael J. Fucci, DO  Last Updated: 12/20/2014

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