Vasovagal syncope is when a person suddenly loses consciousness and faints as a result of overheating, emotional distress, or even the sight of blood

Today is the hottest day of the year for England with temperatures expected to reach highs of 33C in some parts of the country. Whilst this is welcome news for many, for those who suffer from vasovagal syncope, the hot weather may cause some anxiety.

Vasovagal syncope refers to the sudden loss of consciousness and fainting a person experiences when triggered by overheating in warm conditions, severe emotional distress or the sight of blood. Other causes of fainting include medical or dental procedures, pain, long periods of standing still, lack of sleep, or directly after eating or exercise. However this list is not exhaustive and vasovagal syncope can occur randomly.

The condition is sometimes called neurocardiogenic syncope or reflex syncope and is the most common cause of fainting.

Heat syncope is similar to vasovagal syncope but it is caused by overheating specifically. Fainting may caused by long periods spent in the sun on a hot day or queueing in a busy line. Some people may experience heat syncope when they are unacclimated to a hot environment or suffering dehydration.

Vasovagal syncope
© Gorgios

What are the symptoms of vasovagal syncope?

Just before an individual faints, they may have or experience some of the following symptoms:

  • Pale skin
  • Lightheadedness
  • Tunnel vision
  • Nausea
  • Feeling warm
  • A cold, clammy sweat
  • Blurred vision
  • Ringing ears
  • Dilated pupils
  • Jerky, sudden movements
  • Slow, weak pulse

Why do people faint?

Vasovagal syncope occurs when your body overreacts to certain triggers.

Throughout he body there are nerves controlling how fast your heart beats. They also regulate your blood pressure by controlling the width of your blood vessels.

These nerves work together to ensure that your brain is always getting enough oxygen-rich blood.

However sometimes they get their signals mixed up. This is normally when your body reacts to something – like extreme heat or pain – and your blood vessels suddenly open wide and blood pressure drops.

This means that person experiencing a vasovagal attack will lose consciousness and faint as blood pressure plummets.

‘I’d pass out at the most random moments – getting my hair cut, walking down the aisle of a train, getting up from the sofa, in a waiting room.’

A woman in her mid 20s who suffers with vasovagal syncope commented: “For me this started in primary school. I’d pass out at the most random moments – getting my hair cut, walking down the aisle of a train, getting up from the sofa, in a waiting room.”

She describes her symptoms: “I tend to get clammy, sweaty, hot, heart rafting, go lightheaded, see spots and then wake up on the floor having just fainted!”

It was only last year in 2021 that the individual was officially diagnosed with the disorder. She adds: “I started fainting more and more during the pandemic. I think it was because the masks would make me overheat. It also happened after my first Covid-19 jab too.”

How to avoid fainting during the hot weather?

Since individuals who are not acclimatised to the heat are at greater risk of fainting, it is suggested that exercising in hot temperatures should be gradually increased over 10-14 days, allowing the body to get used to the heat.

Dehydration is another major cause of vasovagal syncope because it limits total blood volume and predisposes individuals to syncope. Therefore drinking a lot of water and avoiding alcohol decreases the chances of someone succumbing to heat illness.

Other preventative measures include avoiding exposure to warm and sunny environments, wearing clothing that blocks UV rays, and exercising during cooler times of the day.


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