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Bradycardia

Definition

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

Risk factors that increase your chance of getting bradycardia include:

Symptoms

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

  • Fainting or loss of consciousness
  • Dizziness or light-headedness
  • 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 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.
    • Treat your high blood pressure and/or diabetes .
    • Treat your high cholesterol or triglycerides.

Revision Information

  • American Heart Association

    http://www.heart.org

  • Heart Rhythm Society

    http://www.hrsonline.org/

  • National Heart, Lung, and Blood Institute

    http://www.nhlbi.nih.gov/

  • Canadian Cardiovascular Society

    http://www.ccs.ca

  • Heart and Stroke Foundation of Canada

    http://ww2.heartandstroke.ca

  • Bradycardia. American Heart Association website. Available at: http://www.heart.org/HEARTORG/Conditions/Arrhythmia/AboutArrhythmia/Bradycardia%5FUCM%5F302016%5FArticle.jsp . 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: http://www.nhlbi.nih.gov/health/health-topics/topics/arr/ . Updated July 1, 2011. Accessed January 18, 2013.