Definition

Bradycardia is an abnormally slow heart rate. In adults, it is a heart rate of less than 50 to 60 beats per minute.

The condition can range from mild to life-threatening.

Anatomy of the Heart

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Causes

Bradycardia may be caused by:

• Normal responses to:
  • Deep relaxation
  • Being in excellent physical shape
• Changes in the heart’s natural pacemaker or electrical activity

Risk Factors

Bradycardia is more common in older people. Other things that raise the risk are:

• Heart disease
• Vasovagal syncope
• Endocrine problems, such as hypothyroidism
• Certain medicines
• Exposure to certain toxins
• Low:
  • Blood sugar
  • Potassium or calcium levels
  • Body temperature
  • Blood oxygen
• Other conditions such as:
  • Sleep apnea
  • Systemic lupus erythematosus or sarcoidosis
  • Certain infectious diseases, such as Lyme disease and viral myocarditis
• Head injuries

Symptoms

Bradycardia may have no symptoms. Those who have symptoms may have:

• Fainting or loss of consciousness
• Lightheadedness
• Weakness
• Mild tiredness
• Abnormal heart beats
• Problems breathing
• Chest pain

Some types of bradycardia need emergency care. They can lead to loss of consciousness or sudden cardiac arrest.

Diagnosis

The doctor will ask about symptoms and past health. A physical exam will be done. It will include listening to the heart.

Blood tests may be done to look for underlying problems.

Your doctor may need to test heart function. This can be done with:

• ECG
• Echocardiogram
• A heart rhythm monitor—worn during normal daily activities
• Exercise stress test

Treatment

Treatment may not be needed if there are no heart symptoms or problems. The doctor may monitor the heart rate and rhythm instead.

Those with heart symptoms and problems need care right away. The goal is to reach and maintain a normal heart rhythm.

Treatment may include:

• Stopping any medicines that slow the heart rate
• Diagnosing and treating underlying conditions
• Short-term medicine to increase the heart rate
• An artificial pacemaker to reach and keep a normal heart rhythm—may be short term or lasting (implanted)

Prevention

Bradycardia cannot always be prevented. Some things may help reduce the risk. They are:

• Treating health conditions that might lead to bradycardia
• Carefully following the doctor's instructions for using medicines
• A heart healthy diet, daily exercise, and not smoking