What is Syncope?

Syncope is a temporary loss of consciousness due to insufficient blood flow to the brain, usually described as fainting or passing out.

Vasovagal syncope is the most common type and is also known by other names including neurocardiogenic syncope (favored by cardiologists), vasodepressor syncope, and neutrally-mediated syncope. This form of syncope often occurs when the body overreacts to certain triggers, such as:

  • Acute emotional stress
  • Pain
  • Hunger
  • Sight of blood
  • Prolonged standing
  • Overheating
  • Dehydration
  • Exposure to noxious smelling odors
  • Exhaustion
  • Hyperventilation (excessive breathing that leads to low levels of carbon dioxide in the blood)

The trigger causes a sudden drop blood pressure, resulting in a decline in blood flow to the brain and a brief loss of consciousness. Sometimes the heart rate declines along with blood pressure, but often the heart rate remains unchanged or may actually increase.

While most vasovagal syncope occurs while standing, it does not usually occur immediately upon standing or every time the person stands but occurs only sporadically, often in the context of one of the triggers mentioned above.

Syncope can also be a symptom of a serious cardiac disease such as arrhythmia, heart block, or aortic valve stenosis.

Some medications, particularly antihypertensive medications and diuretics, are associated with an increased risk.

Syncope Symptoms

Symptoms preceding an episode can include:

  • So-called pre-syncopal lightheadedness (a feeling one is about to pass out)
  • Nausea
  • Tunnel vision (vision seems to darken out in the outer circle of visual field and constricts, then may go black while one may still retain the ability to hear what is going on to some degree)
  • Cold, clammy skin
  • Skin paleness
  • Slow, weak pulse
  • Jerky, abnormal movements which usually are seen once someone has actually passed out
  • Infrequently, blood pressure can drop enough to cause a reactive seizure

These symptoms can be associated with other health problems. Contact your doctor if you are having symptoms, and call 9-1-1 if you are having an emergency.

Syncope Treatment

Vasovagal syncope is usually harmless and does not require medical management. Instead, people are advised how to watch for and react to trigger situations.

A doctor may help you identify triggers so that you can avoid them. If that does not work, the doctor may suggest medications or techniques to decrease the pooling of blood in your legs depending on the cause of the syncope. These techniques may include:

  • Foot exercises
  • Wearing compression stockings
  • Tensing leg muscles when standing
  • Increasing salt intake if you do not have high blood pressure
  • Avoiding standing for long periods of time (especially in hot, crowded places)
  • Drinking plenty of fluids

At warning signs of syncope, counter-pressure maneuvers may help prevent loss of consciousness. These maneuvers include:

  • Making a fist with your hands
  • Tensing your arms
  • Crossing your legs
  • Squeezing your thighs together

In some instances, medications that can cause low blood pressure may need to be adjusted.

Rarely, surgery is needed to insert an electrical pacemaker to regulate your heartbeat.

Additional Information

How common is syncope?

Syncope affects about 1 million Americans every year. Approximately one-third of people will have syncope at least once in their lifetime. More than 80 percent of episodes of syncope are vasovagal.

Who gets syncope?

Syncope can occur at any age and in otherwise healthy people. While vasovagal syncope may affect males and females of all ages, it particularly affects younger people, especially females from 12 to 25 years of age.

Some people who experience episodes of syncope have orthostatic hypotension. In this condition, a person’s blood pressure drops immediately or very soon after assuming the upright position due to blood pooling in the legs causing a quick drop in blood pressure. This may occur in the presence of dehydration, anemia, or the administration of too much antihypertensive medication. It is rarely due to damage or malfunction of the autonomic nervous system

How is syncope diagnosed?

Diagnosing vasovagal syncope often involves ruling out other possible causes of fainting, particularly heart problems.

When syncope occurs frequently without explanation, a tilt table test may be used to see if an event can be induced under controlled conditions while a doctor monitors heart rate, blood pressure, the level of oxygen in the blood, heart rhythm, and symptoms while the person is in the head-up position on a table that “tilts” upright to about 70 degrees or so.

The Neurology Department at Barrow Neurological Institute at Dignity Health St. Joseph’s Hospital and Medical Center offers tilt testing. Please call (602) 406-7808 for more information.

Blood tests can be used to test for conditions like anemia (when your body does not have enough healthy red blood cells) and when appropriate to exclude less common but serious other causes, such as adrenal gland insufficiency.

Group 12
Syncope affects about 1 million Americans every year.

Request an Appointment with a Syncope Specialist

Medically Reviewed by Kerry Knievel, DO, FAHS and Terry D. Fife, MD on January 14, 2020