What Is the Main Reason for Bradycardia?

Medically Reviewed on 10/12/2022
Main Reason for Bradycardia
Certain medical conditions may result in slower-than-normal heartbeats, known as bradycardia.

It is difficult to pinpoint one reason for bradycardia.

Bradycardia is the medical term for a heartbeat that is slower than normal for a given age and sex.

  • Most adult hearts beat between 60 to 100 times per minute while at rest.
  • If you have bradycardia, your heart beats less than 60 times per minute at rest.

Though most cases of bradycardia are harmless, a few can be life-threatening. A slow heart rate is typical for some people, primarily young adults, and trained athletes. It generally does not result in any symptoms or health issues.

Several reasons can cause bradycardia, such as:

  • Heart disorders
  • Hormonal dysfunctions
  • Certain medications

Bradycardia may at times be constant or periodic.

10 causes of bradycardia

  1. Sick sinus syndrome: Develops when the heart's natural pacemaker, the sinus node, fails to consistently initiate each heartbeat. The heart rate is slow and erratic because it beats at longer or intermittent intervals. Older adults are more likely to experience sick sinus syndrome, however, it can happen to anyone.
    • The following are risk factors for sick sinus syndrome:
  2. Heart block: The electrical signal that contracts the atria (top chambers of the heart) does not always reach the ventricles. Heart block could be congenital or acquired (after a heart attack). 2:1 heart block occurs when the ventricles only contract once every two times the atria contract.
    • Complete heart block: The upper and lower chambers of the heart are unable to communicate with one another.
    • Congenital heart block: Present from birth
    • The following are risk factors for heart block:
      • Heart illness or a heart attack in the past
      • Exposure to specific poisons like lead or insecticides
      • Specific drugs, such as digitalis
      • Lyme disease
  3. Electrolyte imbalances: Your heart rate could be impacted if you do not consume enough electrolytes, including calcium, magnesium, and potassium.
  4. Infections: If the bacteria that most commonly cause streptococcal infections are not promptly treated, they can potentially harm your heart, particularly your heart valves.
  5. Inflammation: Inflammation of the heart's pericardium (the sac that surrounds and cushions your heart), muscle (myocarditis), or inner lining (endocarditis).
  6. Rheumatic heart disease and fever: When a bacterial illness, such as strep throat, is not treated right away, rheumatic fever may develop. A few years later, rheumatic heart disease develops because of rheumatic fever.
  7. Drugs: Narcotic pharmaceuticals, lithium, beta-blockers, antiarrhythmic drugs, and antidepressants. Cannabis (marijuana), a substance used recreationally, can cause bradycardia.
  8. Lyme disease: Brought on by bacteria transmitted through tick bites. This infection, also called borreliosis, might harm your heart if you wait too long to get treatment.
  9. Chagas disease: Similar to Lyme disease but brought on by a parasite present in triatomine or “kissing bugs,” which are blood-sucking insects.
  10. Other conditions include:


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What are the symptoms of bradycardia?

Some may experience symptoms, fainting, or dizziness, due to bradycardia that need to be investigated and addressed.

The following indications and symptoms may result from slower than normal heartbeats (bradycardia), which may hinder the brain and other organs from receiving enough oxygen:

What are the risk factors for bradycardia?

Bradycardia is frequently linked to heart disease of some kind that has damaged the heart tissue. Bradycardia can become more likely for any reason that raises the risk of heart issues. 

Heart disease risk factors include:

Medically Reviewed on 10/12/2022
Image Source: iStock image

Bradycardia. https://www.mayoclinic.org/diseases-conditions/bradycardia/symptoms-causes/syc-20355474

What is Bradycardia? https://www.webmd.com/heart-disease/atrial-fibrillation/bradycardia

Bradycardia. https://www.cedars-sinai.org/health-library/diseases-and-conditions/b/bradycardia.html

Bradycardia. https://www.hopkinsmedicine.org/health/conditions-and-diseases/bradycardia

Slow Heartbeat. https://upbeat.org/early-warning-signs/slow-heartbeat