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:

        
  • 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

    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:     
  • 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

    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.