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For people with Down syndrome, family members, caregivers and professionals.

Vasovagal Syncope (Fainting)

June 2019 | Brian Chicoine, MD - Medical Director, Adult Down Syndrome Center

What is vasovagal syncope? 

Vasovagal syncope is what we commonly think of as fainting in response to emotional upset or pain. Chen-Scarabelli and Scarabelli (2004) define it as “a transient loss of consciousness, with loss of posture (that is, falling).” Common phrases used to describe it are “fainting,” “passing out,” or “blackout.”


What causes vasovagal syncope? 

Vasovagal syncope (also known as neurocardiogenic syncope) is caused by a triggering of a nervous system reflex that results in a self-limited episode of low blood pressure (hypotension) due to a low heart rate (bradycardia) and dilation of peripheral blood vessels. Vasovagal syncope is caused by an abnormal or exaggerated response of the autonomic nervous system to various stimuli such as standing up and emotion (Chen-Scarabelli & Scarabelli, 2004). 


Is vasovagal syncope common in people with Down syndrome? 

Fainting due to standing up quickly and in response to pain or emotional distress seems to be more common in people with Down syndrome than in people without Down syndrome. Researchers at the Integrative Physiology Laboratory at the University of Illinois at Chicago have observed some differences in the autonomic nervous systems of people with Down syndrome (Hilgenkamp, Wee, Schroeder, Baynard, & Fernhall, 2018). The autonomic nervous system is the part of the nervous system that automatically controls some body functions including blood pressure. Examples of the differences in people with Down syndrome are the tendency to have lower blood pressures and lower resting heart rates. The autonomic nervous system seems to work differently in people with Down syndrome and this seems to put them at a greater risk of fainting. 


What are some things that should be considered when assessing a person who faints?


Anemia (low red blood cell count) can cause fainting. Celiac disease and vitamin B12 deficiency are both more common in people with Down syndrome and can be causes of anemia. Due to differences in pain perception and/or pain reporting, some individuals with Down syndrome may have unreported pain from gastrointestinal ulcers. The first symptom may be fainting due to anemia. 


In our experience, many people with Down syndrome do not drink enough fluids and are at least mildly dehydrated. If the person is in a dehydrated state and then the blood pressure and pulse drop further due to standing or emotional stress, the person may be more likely to faint. 


An underactive thyroid can result in a lower heart rate that could predispose to fainting if the heart rate goes down even further in response to emotional stress or pain. 

Gastrointestinal discomfort

Gastrointestinal discomfort can trigger the autonomic nervous system resulting in lower heart rate and blood pressure. Constipation and celiac disease are both more common in people with Down syndrome and can be associated with gastrointestinal discomfort. 


Other considerations

Heart dysfunction

People who faint, especially someone with a history of congenital heart disease (which is more common in people with Down syndrome), should be considered for a heart evaluation. The evaluation may include an EKG (electrocardiogram), an echocardiogram, and an assessment by a cardiologist. An event monitor or Holter monitor may also be indicated. These devices monitor the electrical activity of the heart continuously for a designated amount of time such as 24 or 48 hours or one week (sometimes longer). We have seen some individuals develop low heart rates that require a pacemaker due to heart dysfunction. 


Consider a diagnosis other than syncope such as seizures. Seizures are more common in people with Down syndrome. The evaluation may include imaging of the brain (CT or MRI) and EEG (electroencephalogram). 


Moyamoya is a rare disease that primarily affects children but can also occur in adults. It occurs when arteries in an area called the basal ganglia at the base of the brain become blocked. It can cause a loss of consciousness or syncope. It can cause a variety of other symptoms, including those associated with having a stroke. More information about moyamoya can be found on the National Institute of Neurological Disorders and Stroke website opens in new window.

Tilt table test

Usually in consult with a cardiologist, a tilt table test can be done. This test assesses the effect of change in position on blood pressure and heart rate. Someone with autonomic nervous dysfunction can have an abnormal response to a tilt table test. 

Other causes

There are other less common causes of fainting. Your health care provider may recommend additional assessment be done as indicated by the history, physical exam, and initial testing. 


How is vasovagal syncope treated? 

  • Increase blood pressure with liquids and salt. Encourage greater fluid and salt intake. Some individuals benefit from putting a glass of water and saltine crackers or pretzels next to their bed and eating the salty food before getting out of bed. 

  • Address possible causes of pain including gastrointestinal (GI) pain. Assess for and treat celiac disease, constipation, heart burn (gastroesophageal reflux disease), and other GI conditions if diagnosed. This will not reduce the autonomic nervous system sensitivity but can reduce the discomfort that can trigger the autonomic nervous system. 

  • Sometimes it is necessary to add a medication that increases blood pressure. A couple examples are midodrine and fludrocortisone. 

The Mayo Clinic website opens in new window has additional information about vasovagal syncope. 

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Please note: The information on this site is for educational purposes only and is not intended to serve as a substitute for a medical, psychiatric, mental health, or behavioral evaluation, diagnosis, or treatment plan by a qualified professional. We recommend you review the educational material with your health providers regarding the specifics of your health care needs.