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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
Factors that may increase your chances of bradycardia:
- Increased age
- Taking certain medications used to treat:
- Exposure to certain toxins
- Cardiac disease, such as:
- Electrolyte imbalances
- Sleep apnea
- Systemic lupus erythematosus or other collagen vascular diseases (rare)
- 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
- 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 .
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 reduce your chances 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:
American Heart Association
Heart Rhythm Society
Canadian Heart Rhythm Society
Heart and Stroke Foundation of Canada
Bradycardia: Slow heart rate. American Heart Association website. Available at: http://www.heart.org/HEARTORG/Conditions/Arrhythmia/AboutArrhythmia/Bradycardia%5FUCM%5F302016%5FArticle.jsp#.Wh2r8FWnFxA. Updated January 5, 2017. Accessed November 28, 2017.
Explore arrhythmia. National Heart, Lung, and Blood Institute website. Available at: https://www.nhlbi.nih.gov/health/health-topics/topics/arr. Updated July 1, 2011. Accessed November 28, 2017.
Overview of arrhythmias. Merck Manual Professional Version website. Available at: http://www.merckmanuals.com/professional/cardiovascular-disorders/arrhythmias-and-conduction-disorders/overview-of-arrhythmias. Updated September 2017. Accessed November 28, 2017.
- Reviewer: EBSCO Medical Review Board Michael J. Fucci, DO, FACC
- Review Date: 11/2018
- Update Date: 12/20/2014