Vasovagal Syncope: Symptoms, Causes, and Treatment

Vasovagal syncope is the most common type of fainting, a temporary loss of consciousness. It’s a condition that happens when your blood pressure and heart rate suddenly drop, delivering less oxygen to your brain. This response usually occurs when your nervous system gets overstimulated by something physically or emotionally stressful, for example, seeing blood or exercising in extreme heat.

About 40% of adults will experience vasovagal syncope in their lifetime. The condition isn’t dangerous, but it can impact your quality of life and lead to injuries if you pass out without warning. Knowing potential triggers and taking certain precautions can help you prevent vasovagal syncope.

Vasovagal syncope is a physical response to stress that leads to fainting. It involves a sudden drop in blood pressure and a slower heart rate that occur when your vagus nerve, a long nerve in your body that helps control these functions, becomes overstimulated.

This overstimulation can cause the part of your nervous system responsible for regulating heart rate and blood pressure to work improperly, leading to feeling faint or passing out. 

What Are Common Triggers?

Not all episodes of vasovagal syncope have a clear trigger. Some common experiences or situations may increase the likelihood of an episode, including:

What Puts You at Risk?

While vasovagal syncope can happen to anyone, some people may be at higher risk. Things that may affect your risk include:

• Age: Fainting episodes occur most frequently in young adults and adolescents, with 85% of fainting episodes happening in people younger than 40 years old. In older adults, more than 50% of fainting episodes are due to vasovagal syncope.
• Family history: People who have family members prone to fainting spells may also experience vasovagal episodes. 
• Anxiety or depression: Research suggests that people who experience vasovagal syncope often have either of these mental health conditions.

Before fainting occurs, you may experience several symptoms that can warn you that you are about to pass out. Some people have little to no warning. Common symptoms can include:

• Dizziness
• Lightheadedness
• Feeling warm or sweaty
• Nausea
• Cold, pale, or clammy skin
• Tunnel vision or blurry vision
• Ringing in your ears

What Does Vasovagal Syncope Feel Like?

If you experience vasovagal syncope, you may suddenly feel warm or sweaty, sick to your stomach, and lightheaded or unsteady. You may also hear ringing in your ears and notice tunnel vision or your vision blacking out. If you do pass out, you’ll likely return to consciousness spontaneously (without any treatment) in a couple of minutes.

Healthcare providers typically diagnose vasovagal syncope by ruling out other conditions. They may look at your medical history and take blood pressure readings while you are standing, sitting, and lying down. You can expect to discuss your family history of cardiovascular (heart) conditions, the potential for blood loss, and any medications you take.

Your healthcare provider may run a series of tests, which may include:

• Blood tests: Your healthcare provider may order bloodwork to rule out underlying health conditions.
• Tilt table test: With this test, you are strapped to a padded table that moves into different angles between lying down and upright positions. Monitors record your blood pressure, oxygen levels, and heart activity throughout.
• Exercise stress test: This test evaluates how your heart responds to different physical activity levels.
• Heart function tests: Your healthcare provider may order an echocardiogram, electrocardiogram, and Holter monitor to examine your heart’s function.
• Neurological tests: These tests help your healthcare provider check for abnormalities in your brain function.

How Serious Is Vasovagal Syncope?

Vasovagal syncope on its own is usually not dangerous. If you experience frequent episodes, the condition can disrupt your quality of life and increase your risk of injuries. Talk to your healthcare provider about whether they recommend you avoid swimming, driving, and heights. Fainting during these activities is extra dangerous.

One study found that among more than 1,100 adults with vasovagal syncope, 23% of people reported an injury, and 3% had a serious injury. Among a total of 2,518 vasovagal syncope episodes, 36% were associated with injuries.

Overall, vasovagal syncope is responsible for up to 1.5% of emergency department visits in the United States.

Healthcare providers don’t usually prescribe medication or other treatment options for vasovagal syncope. Instead, a healthcare provider may advise you to figure out your triggers and then avoid them.

It’s not always possible to prevent vasovagal syncope, but some lifestyle approaches may help reduce the number of fainting episodes. Talk to your healthcare provider for their guidance on these strategies, which may include:

• Drink plenty of fluids.
• Increase your salt intake.
• Engage in moderate exercise.
• Avoid being physically active in high heat.
• Wear compression stockings.
• Discuss any medications you take that lower your blood pressure as a side effect.

It’s also important to take steps to avoid injuries when warning symptoms suggest you’re about to faint. It can help to lie down for 10-15 minutes in a cool area or sit with your head between your knees. Usually, this can help you feel better in a few minutes to a few hours.

It’s important for anyone who has fainted to see a healthcare provider to rule out heart and lung abnormalities or other potential underlying conditions.

If you’ve already been diagnosed with vasovagal syncope, consider seeing a healthcare provider after any fainting to ensure you didn’t injure your head, neck, or limbs when you fell. Regular visits are also important to help make sure your condition is not worsening or that another condition has not developed.

Vasovagal syncope is a temporary loss of consciousness that occurs when your vagus nerve is overstimulated. Things like exercising in extreme heat, straining during a bowel movement, or seeing blood are common triggers for this type of fainting.

Sudden warmth or nausea, ringing in your ears, and tunnel vision are common early symptoms of a vasovagal syncope episode. It’s important to watch for signs that you might faint and take precautions to avoid falling. While the condition itself is not dangerous, fainting can put you at risk for injury.