What Is Vasovagal Syncope?

Giving blood, getting vaccinated, or standing on a stuffy, crowded train can result in dizziness and a loss of consciousness for some people. This reaction is known as a vasovagal syncope episode, also known as fainting. Vasovagal syncope is a temporary loss of consciousness. The vasovagal response, in which your blood pressure suddenly drops, causes you to faint.

Passing out in response to unpleasant conditions can be inconvenient and dangerous. Vasovagal syncope itself, however, is not a problematic health concern. Read on to learn about vasovagal syncope, treatments, prevention, and more.

What Causes Vasovagal Syncope?

Your body reacts in response to certain stimuli by slowing down, known as the Bezold-Jarisch reflex. Everyone has this reflex, regardless of whether you are prone to fainting.

There's first a triggering event, such as being emotionally distressed, overheating, or standing up too quickly. Your body then responds to the discomfort by slowing down. Heart rate and blood pressure drop. This response is extreme in some people. Blood pressure and heart rate may drop so dramatically that you pass out.

Who's More at Risk?

Anyone can faint, although some people are likelier to have an exaggerated Bezold-Jarisch reflex than others. Risk factors include:

• Epilepsy, which is a brain disorder that causes frequent seizures
• Family history of fainting
• Heart disease (e.g., an abnormal heart rhythm)
• Hypoglycemia (low blood sugar)
• Medication use (e.g., anti-anxiety drugs, antidepressants, and blood pressure drugs)
• Substance use disorder

What Are the Symptoms?

Fainting usually lasts several seconds to minutes, and people often feel better within minutes or hours afterward. Several symptoms typically accompany a vasovagal syncope episode.

Vasovagal syncope symptoms include:

• Excess sweating
• Feeling warm
• Lightheadedness
• Nausea
• Pale skin
• Ringing in your ears
• Tunnel vision

How Is It Diagnosed?

A healthcare provider will likely ask questions about the circumstances leading up to the event to determine the cause. A healthcare provider may also administer diagnostic tests to check for an underlying illness.

These tests may include:

• Blood tests: Rules out anemia, or a lack of oxygen-rich red blood cells
• Electrocardiogram (EKG): Checks for an irregular heart rate
• Tilt table testing: Tests your body's response to standing up after laying down

How Is Vasovagal Syncope Treated?

Most people who are prone to vasovagal syncope do not require treatment. Avoiding triggers and lying down when you sense a faint coming on is typically helpful. A small percentage of people who pass out very frequently, however, might require a pacemaker. A healthcare provider inserts this small electronic device to maintain a regular heartbeat.

Prevention 

Passing out in the wrong place or at the wrong time can be inconvenient and dangerous. You may sustain severe injuries if you faint while driving or walking down the steps.

The best strategy is to avoid triggering events. Look away from a needle when giving blood, for example, if you know you faint at the sight. Tell the healthcare provider in advance so they'll have you lie down. Schedule your commute to avoid crowded train cars or extreme temperatures (e.g., a hot yoga class) that may leave you light-headed.

Know the symptoms that precede fainting: lightheadedness, tunnel vision, nausea, and clammy skin. Do your best to lie down promptly if you feel those sensations. You are most vulnerable to that blood pressure drop when standing up. Drinking plenty of fluids to avoid dehydration can also help.

When To Contact a Healthcare Provider

It's not exactly clear why some people are more prone to vasovagal syncope than others. Fainting occasionally is not pleasant, but it's not typically a sign of a severe illness.

Let a healthcare provider know if you faint repeatedly. Get medical attention right away if someone faints and:

• Does not become alert within a couple of minutes
• Has an irregular heart rhythm, chest pain
• Has convulsions, loss of bladder or bowel control, trouble speaking, and vision changes
• Is older than 50
• Is pregnant
• Is severely injured or bleeding

A Quick Review

Vasovagal syncope is a temporary loss of consciousness caused by a sudden drop in blood pressure. Dehydration, emotional distress, heat, and some medications may cause you to faint.

Passing out is typically not a sign of a severe illness, but it can be dangerous. Ensure you recognize vasovagal syncope signs (e.g., lightheadedness, nausea, and tunnel vision). Lay down if you feel like you are going to faint.