How Do You Get Vasovagal Syncope? Fainting Causes

vasovagal syncope, fainting
Vasovagal syncope (fainting) occurs when your heart rate or blood pressure drops suddenly

Have you ever felt lightheaded after seeing something shocking? Or downright fainted? You may have experienced what’s known as vasovagal syncope.

Vasovagal syncope (neurocardiogenic or reflex syncope) occurs when something causes your body to have a sudden drop in heart rate or blood pressure, which leads to reduced blood flow to your brain and a temporary loss of consciousness

Unlike other forms of syncope, vasovagal syncope is usually harmless and doesn’t mean that there’s an underlying problem with your heart or brain.

What triggers vasovagal syncope?

Vasovagal syncope occurs when there’s a triggering event that causes an abnormal response in the part of the nervous system that regulates heart and blood pressure. Your heart rate slows (vagal effect), and your blood vessels in extremities like your legs widen (dilate). The combined drop in both reduces blood flow to your brain, causing you to faint.

Fainting is your body’s way of compensating for this. When you fall, your blood pressure can normalize fairly quickly because your blood can pump from your lower limbs to your heart without having to fight against gravity. 

While there is no classical trigger, common triggers may include:

  • Standing for long periods
  • Excess heat
  • Intense emotional stress
  • Intense physical pain
  • Sight of blood or a needle
  • Prolonged exercise
  • Dehydration
  • Hunger

What are signs and symptoms of vasovagal syncope?

Before fainting, you may experience signs such as:

During a vasovagal syncope episode, people around you may notice:

How is vasovagal syncope diagnosed?

If you have vasovagal syncope, your doctor will make a diagnosis after reviewing your medical history and doing a physical examination. This may include measuring your blood pressure while you’re lying down, seated and then standing. 

Your doctor may order an electrocardiogram (ECG) to evaluate your heart rhythm. They may also try to  rule out other causes with more tests such as:

  • Echocardiogram: Uses ultrasound imaging to view the heart and look for conditions that can cause fainting such as valve problems.
  • Exercise stress test: Studies heart rhythms during exercise, usually conducted while you are walking or jogging on a treadmill.
  • Blood tests: Looks for conditions like anemia that can cause or contribute to fainting spells.
  • Tilt table test: Often used when no heart problems appear to be the cause of the fainting. You lay on your back on a table that changes positions, tilting you upward at various angles. Your doctor monitors heart rhythms and blood pressure during the test to see if changing postures affects you.

How is vasovagal syncope treated?

In most cases of vasovagal syncope, treatment is unnecessary. Your doctor may simply advise you to avoid triggers that can cause the condition to occur. 

However, if you experience syncope so often that it interferes in your quality of life, you may be prescribed treatment such as:

  • Medications: Fludrocortisone acetate, which is a drug that's normally used to treat low blood pressure, may be helpful in preventing vasovagal syncope. Selective serotonin reuptake inhibitors may also help. In extreme emergencies, your doctor may give you an atropine injection to counteract a severely reduced heart rate.
  • Therapies: These may include doing foot exercises, wearing compression stockings or tensing the leg muscles while standing. Avoid prolonged standing especially in hot, crowded places and make sure to drink plenty of fluids.
  • Surgery: If your condition doesn’t get better with other treatments, surgery may be an option, where a pacemaker is inserted into your body to regulate your heartbeat.


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