What is bradycardia?

Bradycardia means your heart rate is slow. This can be completely normal and desirable, but sometimes it can be an abnormal heart rhythm (arrhythmia). If you have bradycardia and you have certain symptoms along with the slow heart rate, then it means your heartbeat is too slow.

A normal resting heart rate for most people is between 60 and 100 beats per minute (bpm). A resting heart rate slower than 60 bpm is considered bradycardia. Athletic and elderly people often have a heart rate slower than 60 bpm when they are sitting or lying down, and a heart rate less than 60 bpm is common for many people during sleep.

The heartbeat

To understand bradycardia, it helps to understand the heart’s electrical system, which is what makes the heart beat.

Your heart has a natural pacemaker called the sinus node (SA node), which is made of a small bunch of special cells. Impulses start at the SA node and move through the walls in the upper chambers of your heart (atria). The impulses cause the atria to contract and push blood into the lower chambers of your heart (ventricles).

Next, the impulse travels down an electrical pathway to the AV node. The AV node is in the center of your heart, in between the atria and ventricles. The AV node acts like a gate that slows the electrical signal before it moves into the ventricles.

The final part of your heartbeat happens when the electricity moves through a pathway of fibers in the ventricles called His-Purkinje Network. This causes the ventricles to contract and force blood out of the heart to the lungs and body.

This cycle is repeated every time your heart beats.

What are symptoms of bradycardia?

You may not have any symptoms of bradycardia. But if you do have a slow heart rate and any of these symptoms, call your doctor:

  • Syncope/passing out
  • Dizziness
  • Weakness
  • Confusion
  • Heart palpitations/fluttering
  • Feeling short of breath
  • Chest pain
  • Lack of energy

Causes of bradycardia

Bradycardia can be caused by:

  • A problem with your SA node (sick sinus syndrome)
  • A problem with your AV node or any of the electrical pathways through the heart (heart block)
  • Illness or medical problems such as:
    • Injury to the heart due to heart attack, endocarditis or a medical procedure
    • Inflammation of the heart muscle
    • Low thyroid function
    • Electrolyte imbalance in the blood
    • Sleep apnea
    • Congenital heart defect
    • Valvular heart disease
    • Lyme disease
  • Certain medications, including beta blockers and heart rhythm medications

Last reviewed by a Cleveland Clinic medical professional on 05/07/2018.

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