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Vasovagal Syncope: What is it and What Should You Do?

Medically reviewed by Nicole Aliling, MD · Neurology · Centre Médicale Internationale

Written by Ruby Anne Hornillos · Updated Dec 15, 2020

Vasovagal Syncope: What is it and What Should You Do?

What causes vasovagal syncope? What is this condition in the first place? This article will look into all things related to this condition. That includes discussing its symptoms and diagnosis.

What is Vasovagal Syncope? 

Vasovagal syncope, or neurocardiogenic syncope, is a condition in which a person suddenly faints because of certain triggers. The usual triggers are the sight of blood and emotional distress. Vasovagal syncope can cause the blood pressure of a person to drop suddenly, which cuts the flow of blood to the brain, causing the loss of consciousness.

Neurocardiogenic syncope is not really harmful nor does it lead to more serious conditions on its own. The main danger posed by this condition is the possibility of injury during an episode. For example, when you lose consciousness all of a sudden, you may hit your head on a hard object or you may get into an accident.

There are other causes of sudden fainting, so your doctor may rule out other possibilities, which are usually more serious. 

Syncope: All You Need to Know

Symptoms of Vasovagal Syncope

Right before fainting due to vasovagal syncope, you may exhibit the following symptoms:

  • Your skin might turn pale right before fainting.
  • You may feel lightheaded all of a sudden.
  • You experience what’s known as tunnel vision, wherein your field of vision narrows and all you see is what’s in front of you.
  • Nausea is also an indicator of this disorder.
  • Another symptom that you might feel right before losing consciousness is a feeling of warmth that might take over your body and which may come with cold sweating.
  • Finally, you may experience blurred vision right before you lose consciousness.
  • None of these symptoms are specific to vasovagal syncope, so a doctor would have to check all the other possibilities.

    Bystanders may observe a person having an episode to exhibit sudden jerky movements that are visibly abnormal. When checked, the person’s pulse will also be noticeably weaker, while the pupils will be dilated. 

    When you lose consciousness because of this condition, you are likely to regain consciousness again after a very short period.  But when you wake up, chances are that you will feel:

    • Very weak
    • Nauseated
    • Lightheaded

    You may even feel disoriented for a few minutes and not know what happened or where you are. 

    What Causes Fainting Spells (Syncope)?

    Causes of Vasovagal Syncope

    So, what is the cause of this condition? 

    Vasovagal syncope happens when the part of the nervous system which controls both the heart rate and blood pressure ceases to function correctly. That breakdown occurs because of certain triggers. One of the most common triggers is the sight of blood. 

    When you react to any of the triggers, your heart rate will slow down and the blood vessels found in your lower extremities will expand. Your blood pool in your lower extremities. The lower heart rate and the low blood pressure will result in reduced flow of blood to the brain. 

    Other common triggers of vasovagal syncope include:

    • Standing for long periods, which can drive blood into the legs of a person.
    • Exposure to too much heat can also be a trigger.
    • Aside from the sight of blood, having blood drawn or even the sight of needles can also be a trigger.
    • Intense fear, especially fear of bodily injury, can also be a trigger.
    • Momentarily holding your breath and exerting effort against a closed glottis (found in the throat), called the valsalva maneuver, can induce vasovagal syncope. This may happen while inducing bowel movements or during fits of coughing.

    The triggers are not limited to these as there are other things that can result in a person losing consciousness because of the lack of blood in the brain.

    When Should You See a Doctor?

    So, when should you see a doctor if you suspect that you are suffering from vasovagal syncope? If you have already been diagnosed with the condition, there is no need to see your doctor after each episode. Though you need to check in with your doctor if you are having more frequent episodes or if you notice that the episodes are happening because of new triggers.

    If you have never had fainting episodes before and you suddenly suffer from one or several, it’s best to seek medical help immediately. 

    There are other medical conditions that can make you prone to fainting and those include:

    Your doctor will examine you and conduct tests to eliminate the possibility that you are suffering from any of these conditions.

    Some medications can also cause you to faint but don’t stop taking your medicines because you suspect it is causing you to faint. Let your doctor confirm it first.

    vasovagal syncope

    How is it Diagnosed?

    As with other diagnoses, your doctor will start with a general check-up and a study of your medical history. They might require an ECG or an EKG to check your heart rhythm. Other tests may include:

    • Exercise stress test
    • Echocardiogram
    • Portable Holter monitor
    • Tilt-table test

    These tests can confirm if you actually have vasovagal syncope or if some other condition is to blame for your fainting.

    Key Takeaways

    Because fainting can be caused by other factors, you need to see your doctor if you suddenly experience fainting spells. Vasovagal syncope is not a dangerous condition but there are other disorders that may have similar symptoms. It’s important that you learn as early as possible.

    Learn more about Brain and Nervous System disorders here. 


    Hello Health Group does not provide medical advice, diagnosis or treatment.

    Medically reviewed by

    Nicole Aliling, MD

    Neurology · Centre Médicale Internationale

    Written by Ruby Anne Hornillos · Updated Dec 15, 2020

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