Vasovagal Syncope

What is vasovagal syncope?

Vasovagal syncope happens when your nervous system overreacts and your blood pressure and heart rate drop suddenly, causing you to faint or pass out. You’re usually unconscious for less than one minute.

This is the most common type of reflex syncope, which happens automatically for reasons you can’t control. People also sometimes call it neurocardiogenic syncope because factors involving your heart, brain or both cause it.

Vasovagal syncope (pronounced “vay-so-vay-gal sin-co-pee”) may seem scary, but this type of fainting is usually harmless.

One out of 3 people will experience vasovagal syncope at least once in their life. It can happen to people of all age groups. In people under 40, most cases of fainting are vasovagal syncope (neurocardiogenic syncope). In older adults, it makes up about half of the cases of fainting.

Most of the time, a vasovagal syncopal episode happens when you’re standing or sitting. It’s rare for it to occur if you’re lying down.

Symptoms of vasovagal syncope

You’re most likely to have symptoms 30 to 60 seconds right before a vasovagal syncopal episode.

Common symptoms include:

• A sudden feeling of tiredness (fatigue)
• A sudden warm feeling
• Lightheadedness or dizziness
• Loss of color in your skin (pallor)
• Nausea
• Profuse sweating
• Slow pulse
• Yawning
• Tunnel vision

Vasovagal syncope causes

Vasovagal syncope is a reflex reaction to something going on around you. But the reflex is either too strong or happens at the wrong time. This all starts in the part of your nervous system that works without you having to think about it — your autonomic nervous system.

One of the key nerves in this system is the vagus nerve, which controls your heart rate and blood pressure. If your vagus nerve becomes too active, it can cause your heart rate and blood pressure to drop too much or too quickly (or both).

If your blood pressure drops too much, this causes vasovagal syncope. You pass out because your brain isn’t getting enough blood flow.

Something happening to you or near you almost always brings on vasovagal syncope. Triggers can be things you see or feel that upset you. Common triggers include:

• Needles or medical instruments. This includes blood draws, blood donations or the sight of certain medical tools or instruments, like scalpels.
• Seeing blood. Fainting at the sight of blood is also a common cause of vasovagal syncope.
• Stress, anxiety or emotional upset. Strong emotions or pain can cause you to pass out.
• Fatigue or exhaustion. Over-exertion, even just from standing too long, can be enough to cause you to pass out.

Complications of this condition

During a vasovagal syncope episode, you may experience:

• Brief disorientation or confusion
• Eyes staying open but rolling up and back into your head
• Falling when you lose consciousness
• Loss of bladder control
• Twitching movements, which people may mistake for a seizure

Once you come to (regain consciousness), you’ll usually recover in about 20 to 30 seconds. Then, you may experience:

• Anxiety or nervousness
• Dizziness
• Fatigue
• Headache
• Nausea
• Pale skin (pallor)
• Sweating
• Urge to poop

A vasovagal syncopal episode can happen again, especially if you stand within 30 minutes of the first fainting episode.

How doctors diagnose vasovagal syncope

A healthcare provider will ask questions about what might have caused you to faint. You should mention any recent changes in your health or unusual symptoms you’ve noticed, even if they don’t seem important. These can help your provider make an accurate diagnosis. A provider will ask you what medications and supplements you take. They’ll also check your blood pressure and heart rate.

A provider may also run the following tests, depending on the circumstances of your symptoms:

• Blood tests. These can detect several conditions that can cause fainting, like low iron in your blood (anemia).
• Electrocardiogram (EKG or ECG). This test measures electrical activity in your heart and may detect an abnormal heart rhythm.
• Echocardiogram. This test shows your heart’s structure. It can identify or rule out an issue that’s causing an abnormal heart rhythm.
• Electroencephalogram (EEG). This test measures electrical activity in your brain. This can help determine if you passed out because of a seizure.
• Tilt-table test. In this test, you lie on a table that a healthcare provider tilts upward. People with vasovagal syncope may pass out or start to pass out during this test.
• Hemodynamic test. This test uses a special type of X-ray (gamma camera) to detect an injected tracer. This shows how your blood circulates and any problems with that.

How do you treat vasovagal syncope?

Most people who have vasovagal syncope will recover on their own. For others, treatment may include:

• IV fluids. These are especially helpful if you’re dehydrated.
• Trigger education and avoidance. Knowing what causes vasovagal syncope can help you avoid that trigger or at least be ready for it. You may be able to avoid passing out entirely.
• Medications. Some medications for heart rhythm disorders or blood pressure may help. These include fludrocortisone and midodrine.
• Compression stockings. Waist-high stockings (medical grade) work best. If you find these too uncomfortable, you can wear compression clothing made for athletes.
• Counter-pressure maneuvers. These include crossing your legs and squeezing your leg muscles tightly for several seconds, as well as interlocking your fists and pulling your arms apart. These maneuvers can help increase your blood pressure and prevent you from fainting.
• Pacing devices. In rare cases, you may need a pacemaker or another device that can help you avoid passing out because of pauses in your heartbeat.
• Catheter ablation. Healthcare providers are using cardioneuroablation to treat rare cases. This targets nerves in your heart.

When should I see my healthcare provider?

If you pass out, you should receive emergency medical care right away. Serious or life-threatening conditions can cause vasovagal syncope. A healthcare provider should examine you right away to determine if a more severe condition caused you to faint.

It’s also essential to get medical attention after passing out if you hit your head (even only slightly). If you’re taking blood-thinning medications, you should always get medical attention after a fall. This is because these medicines give you a much higher risk of internal bleeding.

You should talk to a healthcare provider if:

• You’ve never had a vasovagal syncopal episode before and passed out
• You’ve never had vasovagal syncope before and had several instances where you’ve nearly passed out
• You have a vasovagal syncope diagnosis and your symptoms change or episodes become more frequent

You may want to ask a provider:

• What caused this vasovagal syncopal episode?
• How can I keep it from happening again?
• Do I need more testing?
• Do I need treatment?

Can this be prevented?

You may be able to prevent vasovagal syncope episodes by drinking more fluids, eating more salt and standing up slowly. Talk with your provider before you increase your salt intake, as it increases your blood pressure.

Many people who have vasovagal syncope can limit its impact on their lives. They can learn to recognize the symptoms of a vasovagal syncopal episode and avoid known triggers. Knowing what it feels like before you have an episode can allow you to lie on your back or sit so you don’t get hurt if you fall.

If you can recognize an episode before it happens, you may be able to stop it. Your healthcare provider can teach you techniques that keep your blood pressure high enough so that you don’t pass out. These include:

• Squeezing a foam or rubber ball. Clenching your fist like this may help you stay conscious.
• Arm-tensing. Curl both of your hands like you’re holding something, interlocking your fists. With one hand facing palm-down and the other facing palm-up, hook your curled hands together. Try to pull them apart.
• Leg-crossing. While standing, cross your legs so one knee is behind the other. Keep your balance and then tense up the muscles in your legs, belly and butt.