A vagal episode, also known as vasovagal syncope, is a common cause of fainting that leads to a brief period of unconsciousness. According to Mayo Clinic, the condition is generally harmless, but a person experiencing a vagal episode may become injured upon fainting.
Mayo Clinic notes that a vagal episode occurs when the body overreacts to certain triggers, such as the sight of blood, leading to a temporary decrease in blood flow to the brain due to a drop in heart rate and blood pressure. Symptoms that may precede a vagal episode include lightheadedness, tunnel vision, nausea, cold sweat and blurred vision. If individuals with this condition stand up within 15 to 30 minutes of waking from their episode, they are at risk of experiencing another episode. Fainting may also be a symptom of a more serious condition, so it is important to see a doctor after experiencing a vagal episode.
Common triggers that can lead to vasovagal syncope include standing for extended periods, fear of bodily injury, physical straining and heat exposure. According to Mayo Clinic, vasovagal syncope is diagnosed when alternative conditions are ruled out using electrocardiograms, exercise stress tests and blood tests, among others. Although treatment is typically not necessary, the drug midodrine, used to treat low blood pressure, is commonly prescribed to prevent episodes.