Vasovagal Syncope: Causes, Symptoms, and Treatment

Have you ever felt a little queasy at the sight of blood? Or gotten dizzy and clammy when you hit your funny bone? Perhaps you’ve even passed out after vomiting. 

If this sounds familiar, chances are good that you experienced a vasovagal reaction. This condition, named for the vagus nerve, happens to about half of all people at some point in their lives. When the reaction is severe, it can cause syncope — a medical term for passing out or fainting.

Most of the time, vasovagal syncope is just a nuisance, but for some people it can lead to serious falls and injuries. Knowing the triggers for vasovagal syncope is the first step to getting the condition under control.

What causes vasovagal syncope?

To understand vasovagal syncope, a little knowledge of the vagus nerve is helpful. It travels from behind the brain, through the neck, to organs in the chest and abdomen. The vagus nerve is part of the fight-flight-freeze response, and generally it has a calming effect. It belongs to the parasympathetic nervous system, and it helps to:

• Slow your heart rate 

• Lower your blood pressure 

• Control your rate of breathing

• Allow normal movement of the digestive tract

Problems happen when the vagus nerve overreacts or is overstimulated. This causes the heart rate and blood pressure to drop so low that blood flow to the brain is reduced. 

Things that can bring on vasovagal syncope include: 

• Severe emotional stress 

• Pain 

• Disturbing images

• The sight of blood

• Nausea and vomiting

• Long periods of standing, especially in the heat

• Straining for a bowel movement

• Urination, especially in the middle of the night (also known as “micturition syncope”) 

• Heavy coughing

Dehydration will often make the symptoms worse. For example, someone with diarrhea from a stomach flu or food poisoning may be more susceptible to a vasovagal reaction.

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• Causes of dizziness: Learn about the most common causes of dizziness and when you should seek help.

Why do people get vasovagal syncope?

Although vasovagal syncope is very common, experts aren’t clear on why some people get it and others don’t. In some cases, especially for men, the problem may be genetic.

So far, there’s no cure for vasovagal syncope. So, if you come from a family of fainters, it’s important to avoid things that might trigger an episode.

What are vasovagal syncope symptoms?

Vasovagal syncope refers to the loss of consciousness (fainting) that happens with vasovagal symptoms. These symptoms can include:

• Lightheadedness

• Nausea

• Tunnel vision

• Ringing in the ears

• Sweating and clamminess

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It’s important to recognize the symptoms of vasovagal syncope before they become severe. If your episodes are difficult to manage, you’ll likely be referred to a cardiologist, a healthcare professional who specializes in heart conditions.

Does a vasovagal reaction always result in fainting?

Most of the time, vasovagal symptoms won’t cause you to faint. But you may feel weak, nauseated, and clammy. Usually, you’ll have time to get yourself into a safer position before the symptoms become severe. 

Lying down and propping your feet up above the level of the heart will often make you feel better within a few minutes. This simple action helps blood flow back to the brain, which counteracts the effects of low blood pressure. It’ll also keep you from falling and hurting yourself.

If your case is more severe, you may pass out suddenly and without warning. This can be dangerous. You could break a bone or suffer a concussion from a hard fall if you aren’t able to sit or lie down before losing consciousness. 

How is vasovagal syncope diagnosed?

If you experience a fainting episode, it's important to get a medical checkup. That’s especially true if the episode happens without warning or while driving, or causes a fall or injury. Vasovagal syncope itself isn’t always serious. But it’s important to rule out more serious health issues that could cause fainting. These include problems with heart muscle strength or rhythm, or even neurological conditions like seizures.

What to expect

To make a diagnosis, a healthcare professional will ask about any supplements, over-the-counter medications, or prescription medications that you’re taking. That way, they can be sure that none of these medications are causing trouble for you.

Your initial testing may include:

• A physical exam

• An electrocardiogram (ECG or EKG) 

• Blood work

• Exercise stress testing with EKG

Depending on what this first round of tests finds, your healthcare team may order additional tests. You might need an echocardiogram, which can show the heart’s strength, check the valves, and look for heart damage. 

You may also be asked to wear a heart rhythm monitor. This device records your heart rhythm to check for unusual skips or pauses that might cause you to pass out. 

Even more specialized testing might follow, depending on your results and the severity of your symptoms.

What is the treatment for vasovagal syncope?

In most cases, there’s no specific vasovagal syncope treatment. You’ll be advised to stay well hydrated and avoid the things that can trigger an episode. 

Some of the ways to treat episodes of vasovagal syncope include:

• Sit or lie down when you feel lightheaded

• Cross your legs and tense the muscles of your legs, abdomen, and glutes

• Increase your water and salt intake

• Practice yoga regularly, but avoid hot yoga

• Take medications like beta blockers, midodrine, mineralocorticoids, and selective serotonin reuptake inhibitors (SSRIs)

• Get a pacemaker

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Written by:

Sarah A. Samaan, MD

Sarah Samaan, MD, FACC, FACP, FASE is a board-certified cardiologist who practiced clinical cardiology for nearly 30 years. She is a member of the American College of Cardiology, the American College of Physicians, the American Society of Nuclear Cardiology, and the American Society of Echocardiography.

Edited by:

Mandy Armitage, MD

Mandy Armitage, MD, has combined her interests in clinical medicine with her passion for education and content development for many years. She served as medical director for the health technology companies HealthLoop (now Get Well) and Doximity.

Reviewed by:

Frank Schwalbe, MD

Frank Schwalbe, MD, is an assistant professor of anesthesiology at the Yale School of Medicine. He has practiced anesthesiology for 30 years.

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