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Vasovagal Syncope - Causes, Symptoms, Diagnosis, Treatment, and Prevention

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Vasovagal Syncope - Causes, Symptoms, Diagnosis, Treatment, and Prevention

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When a person faints or loses consciousness due to triggers like emotional stress, it is called vasovagal syncope. Read the article to learn more about it.

Medically reviewed by

Dr. Vijay Kumar Kumawat

Published At November 6, 2019
Reviewed AtApril 4, 2024

What Is Vasovagal Syncope?

Fainting or passing out is called syncope. When one faints because of the overreaction of the body to certain triggers like extreme emotional stress or seeing a snake or blood is called vasovagal syncope or neurocardiogenic syncope. Such triggers drop the heart rate and blood pressure rapidly, which leads to reduced blood flow to the brain. This loss of blood flow is what causes a brief loss of consciousness.

Such episodes of vasovagal syncope are usually harmless and get better without any treatment. One might need treatment if they injure themself while falling when one lose consciousness. As fainting is also a symptom of other serious underlying conditions, doctor will run tests to rule out such diseases.

What Happens During a Vasovagal Syncope?

Special nerves that are present throughout the body help control the heart rate. These nerves also regulate blood pressure by dilating and constricting the blood vessels. Normally, these nerves work in harmony so that enough blood always reaches the brain.

But in cases where some triggers result in the dilation of the blood vessels, these nerve signals get mixed up. This results in a slower heart rate and a drop in the blood pressure, which causes a reduction in the amount of blood reaching the brain. Blood starts pooling in the feet and does not reach the brain, and one pass out. As one lose consciousness and fall or sit, the blood flow to the brain restarts and they feel better.

Vasovagal syncope can affect all groups, and one out of three people are at risk of experiencing the episodes or symptoms once in their lives. The condition is likely to cause fainting or passing out in around 85 percent of people under the age of 40, and almost half in older adults.

What Can Cause or Trigger a Vasovagal Syncope?

Certain triggers that can cause a vasovagal syncope are:

  • Seeing something scary.

  • Having an intense emotional reaction.

  • Standing suddenly after sitting or lying down.

  • Standing for an extended period.

  • Spending a lot of time under the sun (overheated).

  • Intense physical exercise.

  • Severe pain.

  • Severe coughing.

  • Seeing blood.

  • Straining to have a bowel movement.

  • Intense fear of injury.

What Are the Symptoms of Vasovagal Syncope?

Most people do not have any sign or symptom that indicates that they are going to faint. But a few of them have the following signs and symptoms for a brief moment before they fall:

  • Pale skin.

  • Dizziness.

  • Cold and clammy skin.

  • Excess perspiration.

  • Blurred vision.

  • Nausea.

  • Fatigue.

  • Feeling warm.

  • Yawning.

During syncope, the signs include:

  • Dilated pupil.

  • Abnormal jerky movements.

  • Thready pulse.

If an individual is having the above signs before you faint, it is best to sit or lie down so that more blood will reach the brain. This might also prevent you from losing consciousness.

When to See a Doctor for Vasovagal Syncope?

It is best to consult a doctor after an episode of fainting. The doctor might rule out other conditions that cause fainting and will diagnose it as a vasovagal syncope. Get immediate help if along with fainting one notice new symptoms or there are frequent episodes. The following conditions make a person prone to fainting:

Do not stop taking the medicine if one thinks medicines are the cause. Consult the doctor as they will prescribe alternative medicines.

Get immediate medical help in the following situations:

  • If an individual injure their head during the fall.

  • If an individual took more than a minute to regain consciousness.

  • If an individual feel confused after fainting.

  • If an individual have breathing problems, chest pain, or chest tightness.

  • If an individual have speech, hearing, or vision problem.

  • If an individual had a seizure.

  • If an individual is pregnant.

How Is a Vasovagal Syncope Diagnosed?

Tests are done to rule out conditions like heart diseases and diabetes. One might need to get the following tests done:

  • Electrocardiogram - To detect irregular heart rhythms and other heart diseases, by monitoring the electrical signals of the heart.

  • Echocardiogram - Here, high-frequency sound waves are used to produce images of the heart to rule out heart valve problems.

  • Treadmill test or stress test - Here, the heart rate and rhythms are monitored while the patient runs on a treadmill.

  • Blood Tests - To rule out conditions like diabetes and anemia.

  • Tilt Table Test - If all other test results are normal, the doctor might suggest one undergo this test. Here the patient lies flat on a table, and the table tilts from various angles. During this procedure, the heart rhythms and blood pressure are monitored to see if there are changes with the change in position.

What Are the Treatment Options for Vasovagal Syncope?

Vasovagal syncope usually does not need treatment. Try to avoid triggers and prevent head injury when one faint.


Medicines are not very effective in treating this condition. But if one is having frequent episodes, then the doctor might prescribe these medicines:

  • To raise blood pressure - Alpha-1-adrenergic agonists.

  • To raise sodium and fluid levels - Corticosteroids.

  • To regulate the response of the nervous system - Selective serotonin reuptake inhibitors (SSRIs).


To reduce the pooling of blood in the legs, an individual can do foot exercises or wear compression socks.


In case an individual have frequent episodes of fainting, then the doctor might suggest getting a pacemaker. This machine helps regulate the heartbeat.


It is not always possible to prevent these episodes. But an individual can identify and prevent triggers, avoid standing for a long time, consume more salt if their blood pressure is normal, and sit down immediately when an individual start having signs of syncope. For more information on this condition, consult a doctor.

Frequently Asked Questions


What Are The Various Causes Of A Vasovagal Attack?

There are several triggers that are found to cause the vasovagal syndrome. The very common triggers of this attack are listed below:
- At the sight of blood.
- Sudden emotional distress.
- Piercing of a needle.


Can You Recover From a Vasovagal Syncope on Your Own?

People who get into an episode of vasovagal syncope recover by themselves within a few seconds to minutes after fainting and falling onto the ground. This is because of the effect of the earth’s gravity. Once the person has fallen in a horizontal prone position, the pooled blood at the lower limbs is allowed to supply the brain again by gravity. Therefore in the majority of the population, vasovagal syncope is a short term condition.


Does Vasovagal Syncope Run in Families?

There is no exact evidence to prove that vasovagal syncope can be hereditary. But, recent research suggests that vasovagal syncope can be hereditary. It is said to be inherited in an autosomal dominant fashion. It has also been studied that the gene affected in vasovagal syncope is located on chromosome 15.


What Happens in an Episode of Vasovagal Syncope?

Vasovagal syncope occurs when the part of the human nervous system that is responsible for regulating the heart rate and blood pressure starts to malfunction in response to a trigger. During this condition, the heart rate of the affected person begins to slow down. This is followed by the dilation of blood vessels that supply the lower extremities. It increases blood supply to the legs and compromises the blood supply to the brain. This is the reason for the vasovagal syncope.


Can Anxiety Be A Cause Of Vasovagal Syncope?

Emotional triggers are being one of the very common triggers of vasovagal syncope. So, anxiety can not be an exception. Any situation or incident that causes anxiety in a patient can result in a vasovagal syncope episode.


What Are The Different Health Issues That Show Syncope As A Symptom?

Syncope is one of the common symptoms occurring from simple conditions such as dehydration to a severe life-threatening condition such as a heart attack. Every individual experiences syncope at least once in their lifetime. Syncope is a common symptom of the following conditions:
- Dehydration.
- Heavy sweating.
- The pooling of blood in the lower limbs.
- Starvation.
- Dizziness.
- Low blood pressure.
- Abnormalities in the cardiac rhythm.
- Extreme stress.
- Pregnancy.
- Exhaustion.


How Can A Patient Stop Syncope Episodes?

For one to be aware of the syncopal episodes, he or she must always maintain a good nutritional status. The person must avoid standing for a long period. Those who have a previous history of syncope must frequently elevate their legs above their head, in order to maintain adequate blood supply to the cerebrum of the brain. People can also avoid unnecessary stressful and exhausting work.


How Can One Prevent Vasovagal Syncope When Blood Is Being Withdrawn?

If you had a certain degree of giddiness earlier when blood was withdrawn for a test, you have to stay extra careful.
- Tense your grip and your legs so that the blood vessels will constrict. Constriction of the blood vessels will help to avoid unnecessary pooling of blood in the lower limbs. This will ensure adequate blood supply to the brain and prevent syncope.
- When you feel like fainting, slowly lie down on the floor, this will prevent you from getting injured while fainting and falling.


Can Vasovagal Syncope Occur Due To Psychological Reasons?

Yes, at times, vasovagal syncope can be due to psychological reasons too. Any severe form of emotional distress such as fear, anxiety, stress, depression can lead to an episode of vasovagal syncope. For patients who have a history of vasovagal syncope, they must always avoid unnecessary emotional triggers. They should follow up with the doctor's advice properly.


What Are The Effects Of Stress In Vasovagal Syncope?

Yes, stress can be a cause of vasovagal syncope. Sudden stressful situations like knowing the news of their loved one passing away can trigger the vasovagal syncope. Other stressful conditions like workplace pressure and shocking news can cause vasovagal syncope.


Can You Drive If You Have Had A Fainting Episode In recent Days?

Yes, people suffering from vasovagal syncope can drive, but they have certain restrictions. A study proved that people who are affected with vasovagal syncope caused lesser vehicular accidents when compared to that of normal individuals. Usually, individuals involved with a vasovagal syncope can start to drive after a treatment period of three months.


Can Bowel Movements Be A Cause Of Vasovagal Syncope?

Vasovagal syncope is also caused by strain while passing stools or urinating. The reason behind this is that when a person strains to pass stools, due to the pressure, the amount of blood that returns to the heart through the veins is getting reduced. This, in turn, slows down the heart rate. A slow heart rate induces an episode of vasovagal syncope.


What Are The Various Heart Diseases That Can Cause Syncope?

The following heart conditions cause syncope as one of their primary symptoms.
- Heart valve disease, such as mitral stenosis.
- Cardiomyopathy.
- Low blood pressure.
- Abnormalities in the heart rhythm, such as arrhythmia or atrial flutter.
- Congenital heart diseases.


What Should One Do After Recovering From An Episode Of Syncope?

If you have had an episode of syncope, you should do the following once you wake up.
- Slowly sit upright, and support yourself by leaning on a wall or something else.
- Breathe slowly and gently to avoid anxiety.
- Once you are able to walk, eat some nutritious foods, or drink a glass of milk.
- Later, maintain a logbook for your syncope episodes every time you experience it and note the symptoms you experience.
- Check your blood pressure frequently, and consult the doctor for medications to maintain your blood pressure.


What Are The Precautionary Measures One Should Take To Stop a Vasovagal Attack?

- Eat nutritious food and drink plenty of water.
- Increase the dietary salt amount.
- Avoid triggers such as stress and anxiety.
- Stop taking medicines that lower your blood pressure, such as
- Furosemide.
- Practice mindfulness practices such as yoga and meditation to prevent stress and learn to balance stressful situations.


What Are the Different Types of Syncope?

Syncope has been broadly classified into four types based on their causes and the nature of the occurrence. They are
- Vasovagal syncope which is also known as the cardio-neurogenic syncope.
- Situational syncope. In this type of syncope, patients usually faint in response to situations such as coughing, sneezing, defecating, or even after eating a meal.
- Postural syncope which is also known as postural hypotension. This syncope is caused when a person stands for a long duration of time.
- Neurologic syncope. This syncope occurs in response to a neurologic disease such as seizure, tumor, stroke, etc.,


How Can I Stop Vasovagal Syncope?

No, there is no definitive treatment available right now to treat and cure syncope in a patient completely. The outcome of treatment depends on several factors such as the cause of the syncope, age of the patient, presence of comorbidities in the patient, etc., Young individuals have good treatment results when compared to older individuals. All these individuals will have to be always precautious and ready for an episode of syncope.


Why Does Dehydration Cause Vasovagal Syncope?

Yes, dehydration can cause vasovagal syncope. It often occurs along with profuse sweating, exhaustion, and standing for a long period. You should consult your doctor for more details.
Dr. Vijay Kumar Kumawat
Dr. Vijay Kumar Kumawat

General Medicine


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