Vasovagal syncope

Vasovagal syncope (vay-zoh-VAY-gul SING-kuh-pee) is one of the most common causes of fainting. Vasovagal syncope occurs when your body overreacts to certain triggers, such as the sight of blood or extreme emotional distress.

The vasovagal syncope trigger causes a sudden drop in your heart rate and blood pressure. That leads to reduced blood flow to your brain, which results in a brief loss of consciousness.

Vasovagal syncope is usually harmless and requires no treatment. But it's possible you may injure yourself during a vasovagal syncope episode. Also, your doctor may recommend tests to rule out more-serious causes of fainting, such as heart disorders.

Symptoms Causes Prevention

Before you faint due to vasovagal syncope, you may experience some of the following:

  • Skin paleness
  • Lightheadedness
  • Tunnel vision — your field of vision is constricted so that you see only what's in front of you
  • Nausea
  • Feeling of warmth
  • A cold, clammy sweat
  • Yawning
  • Blurred vision

During a vasovagal syncope episode, bystanders may notice:

  • Jerky, abnormal movements
  • A slow, weak pulse
  • Dilated pupils

Recovery after a vasovagal episode begins soon after fainting, generally in less than a minute. However, if you stand up too soon after fainting — within 15 to 30 minutes or so — you're at risk of fainting again.

When to see a doctor

Because fainting can be a sign of a more serious condition, such as a heart or brain disorder, you may want to consult your doctor after a fainting spell, especially if you never had one before.

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