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What is syncope?

Syncope is a temporary loss of consciousness and muscle tone caused by inadequate blood supply to the brain. Syncope is sometimes also called fainting.

Syncope accounts for 1 percent to 3 percent of emergency room visits and 6 percent of hospital admissions, according to the American Academy of Family Physicians.

What causes syncope?

The common reason behind each syncopal or fainting episode is a temporary lack of oxygen-rich (red) blood getting to the brain. However, many different problems can cause a decrease in blood flow to the brain. Some types of syncope include:

  • Vasovagal syncope. This is the most common type of syncope. A variety of situations stimulate the vagus nerve, which leads to a slowing of the heart rate and dilation of the body's blood vessels. With a slow heart rate and dilated blood vessels, less blood gets to the brain, and fainting occurs. Pain and emotional stress can trigger vasovagal syncope in susceptible people. This type of syncope can happen more often in some families.

  • Orthostatic hypotension. Another cause of syncope is orthostatic hypotension. This is a drop in blood pressure that occurs when a person has been standing for awhile, or changes from a sitting to a standing position. Blood tends to pool in the legs, keeping a normal amount of blood from being returned to the heart, and thereby preventing a normal amount of blood from leaving the heart and going to the body. A momentary drop in blood flow to the brain occurs, and a person faints.

Some children have abnormalities of the structures of the heart that can cause syncopal episodes. Heart defects causing "outflow obstruction" may produce fainting because they restrict the blood flow to the body out of the left ventricle. Aortic stenosis and hypertrophic cardiomyopathy diminish the blood flow from the left ventricle through the aorta, and children with these problems may experience syncope.

Irregular or rapid heart rhythms can also trigger syncope. When the heart beats rapidly or irregularly, the ventricles have less time to fill with blood before it is time to pump whatever blood is within them to the lungs or to the body. Not as much blood as normal leaves the heart and flows through the aorta with these abnormal rhythms, and the body reacts to the diminished blood flow to the brain by fainting.

Yet another cause of syncope can be an inflammation of the heart muscle known as myocarditis. The heart muscle becomes weakened and is not able to pump as well as normal. The body again reacts to decreased blood flow to the brain by fainting.

Other situations or illnesses that can cause syncope include, but are not limited to, the following:

  • Head injury

  • Epilepsy

  • Stroke

  • Inner ear problems

  • Dehydration

  • Low blood sugar

  • Breath holding episodes

What are the symptoms of syncope?

The following are the most common symptoms of syncope. However, each child may experience symptoms differently. Also, the symptoms of syncope may resemble other conditions or medical problems. Consult your child's health care provider for a diagnosis.

Some children will experience presyncope, which is the feeling that they are about to faint. Your child may be able to tell you that he/she is "about to pass out," "feels like I might faint," "feels like the room is spinning," or "feels dizzy." These sensations usually occur immediately before fainting occurs. There may be enough warning to enable your child to sit or lie down before loss of consciousness occurs; this can prevent injuries that may occur due to falling during syncope.

In other instances, the child will have no presyncopal sensations, but will simply faint.

Should my child be seen by a physician after fainting?

Some types of syncope are caused by a serious problem, so it is recommended that your child be seen by a health care provider to determine the reason for all fainting spells.

How is the cause of syncope diagnosed?

Your child's health care provider will obtain a medical history and perform a physical examination. The details about the syncopal episodes are helpful in pinpointing the cause: how often they occur, what activity your child was participating in prior to fainting, if there were any presyncopal sensations, and other symptoms provide useful information. Blood pressure may be taken in sitting and standing positions to check for orthostatic hypotension.

Other diagnostic tests may include:

  • Blood tests. These help to evaluate causes such as low blood sugar and dehydration.

  • Electrocardiogram (ECG or EKG). This is a test that records the electrical activity of the heart, and shows abnormal rhythms (arrhythmias or dysrhythmias).

  • Tilt table test. The child's blood pressure and heart rate are measured while lying down on a board and again after the board is tilted up.

  • Holter monitor. This portable EKG machine is worn for a 24-hour period or longer to evaluate irregular, fast, or slow heart rhythms while engaging in normal activities.

  • Echocardiogram (echo). This is a procedure that studies or evaluates the heart's function by using sound waves to produce a moving picture of the heart and heart valves.

Treatment for syncope

Specific treatment for syncope will be determined by your child's health care provider based on:

  • Your child's age, overall health, and medical history

  • Extent of the condition

  • Cause of the condition

  • Your child's tolerance for specific medications, procedures, or therapies

  • Expectations for the course of the condition

  • Your opinion or preference

For vasovagal syncope, avoiding the situations that trigger the episodes is recommended.

For illnesses causing syncope, such as irregular heart rhythms or epilepsy, medications may be prescribed by your child's health care provider to help control the disease.

With outflow obstructions, surgical repair of the heart problem may be indicated. Consult your child's health care provider regarding specific information for your child.