Vasovagal Syncope: A Common Cause of Fainting (2024)

You won’t die from vasovagal syncope on its own. However, the suddenness of the reaction and temporary loss of consciousness that follows can lead to dangerous falls and injuries.

Vasovagal syncopesuddenly develops when your body reacts so strongly to a trigger—like seeing blood or being scared—that you faint. Your heart rate and blood pressure plummet, but the heart doesn’t stop.

An episode of fainting from vasovagal syncope usually only lasts seconds to minutes. For example, fainting while sitting in a chair while having your blood taken could be an episode of vasovagal syncope.

Symptoms of Vasovagal Syncope

Fainting from a vasovagal response can be sudden and unexpected. However, you may have warning signs a few seconds or minutes before a fainting episode.

The signs leading up to fainting are called theprodromeof syncope, or pre-syncope. The symptoms that come on after you regain consciousness are calledpostdromal symptoms.

Prodromal Symptoms

Prodromal symptoms of syncopecan include:

• Lightheadedness
• Trouble hearing
• Visual disturbances, such as “gray out” or tunnel vision
• Sudden sweating
• Nausea
• Palpitations
• Pallor (pale appearance)

A sensation of “graying out” is when the colors and light around you get dim. The visual changes are followed by a loss of consciousness.

The time between when prodromal symptoms come on and when you actually pass out can last for a few seconds.

Vasovagal Episode Symptoms

Episodes of vasovagal syncope have several key symptoms and features that make them different from other causes of fainting:

• The episodes almost always occur while you’re standing or sitting up. This is because more blood goes to your legs when you are standing and your blood pressure drops. Fainting almost never happens when someone is lying down.
• You will usually regain consciousness shortly after falling or being helped to the ground. This is because your normal blood pressure is restored in the lying-down position.
• Being held up won’t help. If someone tries to hold you up during a vasovagal episode, being in a standing position can actually prolong the time you are unconscious.

Postdromal Symptoms

After an episode of vasovagal syncope, many people will feel nauseous, dizzy, and very tired. These symptoms can last anywhere from minutes to hours.

You are at risk of fainting again until these symptoms go away. You will need to avoid driving, climbing ladders, or doing anything that would be dangerous for you or others around you should you pass out.

You should also be aware of the warning signs of another fainting episode and take steps to try to prevent it.

What to Do

If you think you might faint from vasovagal syncope, there are some steps you can take to stay safe.

Stay calm but know that you don’t have long to keep a fainting spell from happening—maybe five to 10 seconds.

• If you feel like you’re about to faint, you might be able to prevent it by lying down with your legs up or sitting in a chair with your head between your knees. Wait until you feel better before trying to get up.
• If there’s no chair or surface to sit on, try to lower yourself down to the floor and lie down. The goal is to make sure that you are as close to the ground as possible so that you won’t get hurt on the way down if you pass out.
• If your clothes are tight (for example, you have a scarf around your neck or a tightly buttoned-up shirt) try to loosen them up.

If you faint because you have vasovagal syncope, there are a few things you can do to take care of yourself after it happens:

• If you are not injured, lie down with your feet slightly elevated (use a pillow, a coat, or whatever is handy). Stay in this position for about 10 minutes. Don’t get up too fast, as you could faint again.
• Try to rest somewhere with fresh air that’s not too warm.
• Take slow, deep breaths. Try to avoid hyperventilating if you’re anxious.
• If you think you might be dehydrated or have low blood sugar, you may need a glass of water or juice and a snack. If you think that your blood pressure is too low, eating something salty or having an electrolyte drink may help.

What Triggers Vasovagal Syncope?

Vasovagal syncope happens when something triggers thevasovagal reflex, which causes blood vessels to widen (dilate) suddenly. Dilation of the blood vessels causes a lot of the blood in the body to pool in the legs.

The pooling of blood is accompanied by a slowing heart rate, which leads to a drop in blood pressure. If the drop in blood pressure is big enough that the brain isn’t getting the oxygen it needs, a person faints.

Common Triggers

Vasovagal syncope is a reflex syncope, meaning it’s a response to a stimulus, including physical and psychological stress. Common triggers of vasovagal syncope include:

• Dehydration
• Bleeding
• Sudden, severe pain
• Having your blood drawn
• Being exposed to a traumatic sight or event
• High levels of stress, anxiety, or fear
• Straining while urinating or having a bowel movement
• Severe coughing
• Hyperventilation (breathing too fast)
• Standing still for long periods of time, especially if you lock your knees
• Overexerting yourself in hot weather
• Excessive alcohol or substance use

There’s a strong link between vasovagal syncope and anxiety, and it can have a cyclical effect. Strong feelings of stress and anxiety can be a trigger for syncope, and repeated fainting spells can raise anxiety levels and lead to mental health conditions like depression.

Who’s at Risk for Vasovagal Syncope?

The reflex that causes vasovagal syncope can affect anyone and fainting spells are common. However, some people are more at risk of fainting from vasovagal syncope than others.

Young Adults and Adolescents

Vasovagal syncope can occur at any age but is more common in adolescents and young adults.

More than 85% of fainting episodes in people younger than 40 years of age are from vasovagal syncope and about half of fainting episodes in older adults are caused by it.

Recurrent Syncope

Some people are more likely to have vasovagal episodes than others and might be easily triggered.

People who are just more prone to fainting spells generally notice they start when they’re in their teens and can be triggered by a variety of things, like the sight of blood.

Dysautonomia

Some people have frequent vasovagal syncope that is so hard to treat that they become disabled by it. Often, the fainting is linked todysautonomia, an imbalance of theautonomic nervous system.

The autonomic nervous system controls body functions like our heartbeat and breathing. Dysautonomia makes a person more prone to the vasovagal reflex that causes syncope.

Fainting is usually accompanied by other symptoms of dysautonomia, such as:

• Abdominal bloating or cramps
• Diarrhea
• Constipation
• Extreme fatigue
• Various aches and pains

When to See a Healthcare Provider

It’s a good idea to contact your healthcare provider after you’ve fainted unexpectedly—especially if you’ve never fainted before.

If you’ve been diagnosed with vasovagal syncope, call your provider if you are pregnant or have recurrent episodes of fainting. If you have heart problems, syncope could be a warning sign of something more serious.

Get medical attention right away if you have other symptoms before you faint, such as:

• Blurred vision
• Chest pain
• Confusion
• Trouble talking
• Shortness of breath
• Irregular heartbeat

How Is Vasovagal Syncope Diagnosed?

To diagnose vasovagal syncope, your healthcare provider will review your symptoms, medical history, and family history. You’ll also be asked about the events leading up to your fainting episode.

In addition, your provider might want to do these common tests:

• Physical exam, which includes listening to your heart and breathing sounds and measuring your blood pressure
• Blood tests
• Heart function tests: electrocardiogram (ECG), Holter monitor, echocardiogram, stress test and/or electrophysiology study
• Tilt table test
• Neurological tests to test brain function

Your provider may want to do imaging tests like an X-ray, MRI, or CT scan if they want to check a specific part of your body more closely, like your chest or head, though these tests are less commonly used to diagnose fainting.

The results of these tests help your provider rule out other, sometimes more serious causes of fainting:

• Orthostatic hypotension, a condition where your blood pressure falls when you stand up, making you feel dizzy or lightheaded
• Postural orthostatic tachycardia syndrome (POTS), a condition where you get lightheaded and have heart palpitations (irregular beats) when you stand up
• Low red blood cell count (anemia)
• Seizures
• Heart conditions or problems
• Diabetes if blood sugar levels are too high or too low
• Conditions that affect your brain, like a transient ischemic attack
• Lung problems resulting in a lack of oxygen (hypoxia)
• Breathing too fast or too hard (hyperventilation), such as when you’re scared or anxious
• Certain medications and substances
  

How Is Vasovagal Syncope Treated?

People who have a single, one-time episode of vasovagal syncope generally do not need any medical treatment. If you have recurrent fainting episodes, you should talk to your provider.

Fainting episodes can come at inconvenient, impractical, and unsafe times. While vasovagal syncope is not life-threatening, the consequences of fainting can be. For example, falls can cause serious injuries, and fainting behind the wheel could lead to a car accident.

Treatment for vasovagal syncope usually includes a combination of strategies like medication and exercise.

Medications

Certain medications can help regulate blood pressure and heart rate and may help people with vasovagal syncope, including:

• Midodrine (causes narrowing of the blood vessels)
• Droxidopa (constricts blood vessels)
  
• Fluoxetine (a selective serotonin reuptake inhibitor used to treat depression and anxiety)
• Theophylline (used to treat asthma)
  

Exercises

An episode of vasovagal syncope can sometimes be stopped by immediately doing exercises that tense the muscles. When the muscles are tense, it reduces blood vessel dilation and increases the amount of blood being returned to the heart.

Examples of exercises that may help prevent fainting from vasovagal syncope include:

• Crossing your legs and squeezing them together
• Tensing your arms with clenched fists
• Tensing your leg muscles, abdomen, and buttocks
• Squeezing a rubber ball

A pacemaker(a device that regulates the heartbeat) used to be suggested for people with vasovagal syncope, but research has shown it is not helpful.

How Can You Prevent Vasovagal Syncope?

If you’ve had one or two episodes of vasovagal syncope, you’ve probably learned to spot the warning signs. You may even be able to prevent an episode by lying down and elevating your legs.

However, trying to “fight off” an episode of vasovagal syncope by forcing yourself to stay standing or sitting up and “willing yourself” not to faint almost never works.

The best thing you can do to prevent fainting is to avoid your triggers—for example, excessive heat, stress, dehydration, pain, and prolonged standing.

If you have low blood pressure, consider talking to your provider about whether increasing your salt intake could help you avoid fainting episodes.

Summary

Vasovagal syncope happens due to a sudden drop in blood pressure and heart rate. It can be triggered by events like an anxiety attack or a blood draw. Recovery usually starts within seconds or minutes, but you may need 10 minutes or more before standing back up so you don’t faint again.

See a healthcare provider if you had an episode of fainting, especially if it’s your first time or you have multiple episodes. Your provider can run tests to rule out other causes of fainting, some of which can be serious.

Learning your triggers and trying to avoid them is the best way to prevent vasovagal syncope. Medications and/or certain exercises can also help. If you feel an episode coming on, try to prevent it by lying down with your legs elevated.