Bradycardia

Definition

• 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

• 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

• Increased age
• Hypothyroidism
• Taking certain medications used to treat:
  • High blood pressure
  • Alzheimer’s disease
  • Heart disease
  • Heart failure and arrhythmias
• Exposure to certain toxins
• Cardiac disease, such as:
  • Heart attack
  • Wearing out of the heart's conduction system
  • Congestive heart failure
  • Heart valve failure
  • Heart conditions that are inherited or present at birth
• Electrolyte imbalances
• Sleep apnea
• Lupus or other collagen vascular diseases (rare)
• Head injuries
• Hypothermia
• Hypoglycemia
• Infectious diseases, such as:
  • Diphtheria
  • Rheumatic fever
  • Viral myocarditis
  • Lyme disease
  • Chagas disease

Symptoms

Diagnosis

• 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:
  • Electrocardiogram
  • Echocardiogram
  • A portable, continuous heart rhythm monitor that you wear as you perform normal daily activities
  • Exercise stress test
  • Nuclear scanning
  • Coronary angiography

Treatment

• 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

• 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.

RESOURCES

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 RESOURCES

Canadian Cardiovascular Society http://www.ccs.ca

Heart and Stroke Foundation of Canada http://ww2.heartandstroke.ca

References

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.

Revision Information

• Reviewer: Michael J. Fucci, DO
• Review Date: 09/2012 -
• Update Date: 01/18/2013 -