A Transient Loss of Consciousness

Syncope is a transient loss of consciousness, described as fainting or passing out. It usually relates to a temporary insufficient flow of blood to the brain. Syncope is a common condition, which can occur at any age and in people without other medical problems.

Symptoms of Syncope

  • Blacking out
  • Feeling lightheaded
  • Falling for no reason
  • Dizziness
  • Fainting, especially after eating or exercising
  • Changes in vision, such as seeing spots or tunnel vision.


  • Neurally mediated syncope (NMS), the most frequent cause of fainting, is benign. It is most common in children or young adults, but can occur at any age. If this type of syncope is prolonged, it can trigger a seizure.
  • Cardiac syncope is caused by a heart or blood vessel condition that affects blood flow to the brain. These conditions can include arrhythmia, structural heart disease, blockages in the cardiac blood vessels, valve disease, aortic stenosis, blood clot, or heart failure.


Syncope can result from a sudden drop in blood pressure or heart rate, or changes in the amount of blood in areas of your body (such as from a violent coughing fit).

Syncope can have cardiovascular, neurological, or psychiatric causes. However, the most common cause is an overreaction of the body to certain triggers, such as the sight of blood or extreme emotional distress. It can also be caused by overheating, dehydration, heavy sweating, or exhaustion.

Syncope may suggest a serious disorder if:

  • It occurs with exercise
  • It is associated with palpitations or irregularities of the heart
  • There is a family history of recurrent syncope or sudden death.


  • The majority of children and young adults with syncope have no structural heart disease or significant arrhythmia. A careful physical examination by a physician, including blood pressure and heart rate measured lying and standing, is generally the only evaluation required.
  • In other cases an electrocardiogram is used to test for abnormal heart rhythms. Other tests, such as echocardiogram, treadmill stress test or Halter monitor, may be needed to rule out other cardiac causes of syncope.


  • To help prevent syncope, people with NMS should be on a higher salt diet and drink plenty of fluids to avoid dehydration and maintain blood volume. They should watch for the warning signs of fainting – dizziness, nausea and sweaty palms – and sit or lie down if they feel the warning signs.
  • Some people may respond to medication.

How to get involved

Contact us if you are interested in becoming involved in arrhythmia research and you fit the following criteria:
– Have significant experience of living with an arrhythmia
– Are in a period of stable health
– Have a constructive critical attitude and a certain distance from your own story
– Are willing to help people by working with both patients and health professionals and researchers

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