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Syncope

  • Syncope is the medical term for fainting. It’s a temporary loss of consciousness and muscle tone that occurs when not enough blood goes to the brain.

    • Fainting affects people of all ages.
    • More than 100,000 adults and children visit a doctor each year because of fainting.

    General Pediatrics
    Boston Children's Hospital

    300 Longwood Avenue
    Boston MA 02115
    617-355-6714 

  • What is syncope? 

    Syncope is the same thing as fainting. It’s a temporary loss of consciousness and muscle tone that occurs when not enough blood goes to the brain.

    Syncope affects people of all ages, from toddlers to the elderly. More than 100,000 adults and children visit a doctor each year with complaints of fainting spells.

    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. Many different problems can cause a decrease in blood flow to the brain. Types of syncope include: 

    • Vasovagal syncope
      • most common type of syncope
      • occurs when the vagus nerve is stimulated, 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
      • triggers include pain and emotional stress
      • can happen more often in some families
    • Orthostatic hypotension
      • 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 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.

    Who is at risk for syncope?

    Some children have abnormalities of the structures of the heart that can cause syncopal episodes. Heart defects causing "outflow obstruction" may restrict the blood flow to the body out of the left ventricle, causing them to faint.

    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 also can 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: 

    What are the symptoms of syncope? 

    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 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 so that your child will be able to sit or lie down before fainting. This can prevent injuries that may occur due to falling.

    In other instances, your 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 we recommend that your child be seen by a doctor to determine the cause of all fainting spells. 

    During your appointment, your child's doctor 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 doing before fainting
    • if he had any presyncopal sensations

    Blood pressure may be taken in sitting and standing positions to check for orthostatic hypotension. 

    Other diagnostic tests may include:   

  • 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 physician to help control the disease.

    If your child has a heart condition, surgical repair of the heart problem may be necessary.

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