Overview
Vasovagal syncope (vay-zoh-VAY-gul SING-kuh-pee) occurs when you faint because your body overreacts to certain triggers. These may include the sight of blood or extreme emotional distress. Vasovagal syncope also is called neurocardiogenic syncope.
The vasovagal syncope trigger causes your heart rate and blood pressure to drop suddenly. That leads to reduced blood flow to your brain, causing you to briefly lose consciousness.
Vasovagal syncope is usually harmless and requires no treatment. But it's possible that you may injure yourself during a vasovagal syncope episode. Your healthcare professional may recommend tests to rule out more-serious causes of fainting, such as heart conditions.
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Symptoms
Before you faint due to vasovagal syncope, you may experience some of the following symptoms:
- Change in skin color.
- Lightheadedness.
- Tunnel vision — your field of vision narrows so that you see only what's in front of you.
- Upset stomach.
- Feeling warm.
- A cold, clammy sweat.
- Blurred vision.
During a vasovagal syncope episode, people around you may notice:
- Jerky movements.
- A slow, weak pulse.
- Dilated pupils.
Recovery after a vasovagal episode generally begins in less than a minute. However, if you stand up too soon after fainting — within about 15 to 30 minutes — you're at risk of fainting again.
When to see a doctor
Fainting can be a sign of a more serious condition, such as a heart or brain condition. You may want to consult your healthcare professional after a fainting spell, especially if you've never had one before.
Causes
Vasovagal syncope occurs when the part of your nervous system that regulates heart rate and blood pressure overreacts to a trigger. Common triggers include:
- Standing for long periods of time.
- Heat exposure.
- Seeing blood.
- Having blood drawn.
- Fear of bodily injury.
- Straining, such as to pass stool.
Vasovagal syncope can happen without a trigger.
During a vasovagal syncope episode, your heart rate slows, and the blood vessels in your legs widen. This allows blood to pool in your legs, which lowers your blood pressure. The drop in blood pressure and slowed heart rate quickly reduce blood flow to your brain, and you faint.
Risk factors
The risk of vasovagal syncope may be higher in:
- Children and young adults, although vasovagal syncope can happen at any age.
- People who stand for long periods of time.
Prevention
You may not always be able to avoid a vasovagal syncope episode. If you feel like you might faint, lie down and lift your legs. This allows gravity to keep blood flowing to your brain. If you can't lie down, sit down and put your head between your knees until you feel better.
Feb. 15, 2025