What is syncope?

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

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 causes 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. This is a drop in blood pressure that occurs when a person has been standing for a while, or changes from a sitting to a standing position. Blood pools in the legs, preventing a normal amount of blood from being pumped to the brain. This momentary drop in blood flow to the brain causes a person to faint.

  • Heart disease. Rarely, there are abnormalities 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 and brain.  

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, 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

  • Seizure

  • Stroke

  • Inner ear problems

  • Dehydration

  • Low blood sugar

  • Breath holding episodes in young children

  • Pregnancy

  • Anemia

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 look like 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 doctor 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 do a physical exam. The details about the syncopal episodes are helpful in pinpointing the cause. Helpful details include how often the syncope occurs, what activity your child was participating in prior to fainting, if there were any presyncopal sensations, eating history, your child's medications and medical conditions, and any family history of heart disease in young people. Blood pressure may be taken in sitting and standing positions to check for orthostatic hypotension.

On the basis of the history you provide, other tests can include:

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

  • Electrocardiogram (ECG). 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. This is helpful to diagnose orthostatic hypotension. 

  • Holter monitor. This portable ECG 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 the history and physical exam. For the most common causes of syncope, staying hydrated (taking in enough water and liquids) and maintaining a good diet can prevent future episodes. When your child feels faint, lying or sitting down with the head lower than the heart should be encouraged to increase blood flow to the brain and prevent fainting.

If there is an underlying condition, such as heart disease, that is causing the syncope, you may be referred to a specialist, such as a cardiologist, for medication and further evaluation.