Bradycardia

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:

  • 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

  • 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
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  • 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

  • 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.

  • 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
    .

  • 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