What causes fainting spells?

ESCANABA – If you have ever fainted or nearly fainted, the event probably caused you some degree of worry, even if you never reported it to your doctor. In fact, fainting is fairly common; about 40 percent of Americans have fainted at least once. In most cases it is not associated with any major medical concern.

Known medically as syncope, fainting is caused by a brief episode of impaired blood flow to the brain. This is typically caused by low blood pressure, low blood volume or a change in the heart’s pumping action. Fainting is not the same as a concussion, stroke or seizure all of which may involve loss of consciousness but can have much more severe consequences.

The vast majority of fainting episodes occur in two age groups: adolescents and adults age 65 and over. Some people get a warning ahead of time lightheadedness, sweating and weakness particularly in the legs. If you learn to recognize these signs and act fast enough, you may be able to avoid the actual syncope by sitting or lying down.

When you faint, you black out only briefly then return to normal consciousness. Should you hit your head during the fall, you may, however, have a concussion as a result. In either case, it’s a good idea to see your doctor and find out what caused the episode.

Common among teenagers is a specific form of fainting known as vasovagal syncope, which may occur in stressful, frightening, embarrassing or uneasy situations. These may include blood draws or school tests. Again, the culprit is low blood pressure in the vessels leading to the brain, but the change occurs as a result of action by the vagus nerve, which controls the release of the neurochemicals adrenaline and acetylcholine. When too much acetylcholine is released, the heart rate slows and blood vessels dilate, making it more difficult for the heart to combat gravity in pumping blood to the brain.

Young females who “swoon” in 18th and 19th century novels suffer from vasovagal syncope. Some swoon when they hear bad news; others, when they see blood or a gory scene. These women were also likely squeezed into tight corsets, resulting in compression of nerves and blood vessels, another reason for syncope. Pregnant women are also at risk of this type of fainting, particularly if they have been standing for an extended period, allowing blood to pool in their legs.

The most common reason for fainting among youth, vasovagal syncope ordinarily does not require medical intervention, only some care in avoiding situations that might trigger a collapse. Again, though, it is important to discuss a fainting episode with your doctor. Diagnosis of a young person who has fainted may include a suspicion of heart problems and perhaps a few tests. Some youth most notably athletes have an abnormal thickening of parts of the heart muscle. When the heart is asked to beat harder during competition, this thickened area may obstruct blood as it tries to leave the heart. This is a frequent cause of sudden death in high-level athletes.

For senior citizens, problems occur more often after a period of inactivity, followed by some type of action. For instance, an older adult who has been sitting in the theater for nearly two hours may experience a drop in blood pressure when he suddenly standing up. This is known as postural or orthostatic hypotension. The solution is to stand up more slowly and pause a moment or two before starting to walk to give blood pressure time to adjust.

Most fainting spells are not cause for alarm, although the risk of suddenly falling has dangers. Also, episodes of lightheadedness may be a sign of a more serious condition called atrial fibrillation, an arrhythmia of the upper chambers of the heart that may cause the heart to beat erratically and faster or slower than normal, sometimes reducing blood flow to the brain.

Even one episode is not something to ignore or deny. Err on the side of caution and see your doctor.

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EDITOR’S NOTE: Dr. Nagano is a board certified family practice physician with OSF Medical Group. She sees patients in Suite 104 of the OSF Medical Office Building.