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


The primary reason for all fainting episodes is a lack of blood supply to the brain, but many different problems can disrupt blood flow:

  • Vasovagal syncope is the most common type. The vagus nerve is stimulated by pain or emotional stress, leading to slowing of the heart rate and dilation of the body's blood vessels. As a result, less blood gets to the brain and fainting occurs.
  • Orthostatic hypotension is a drop in blood pressure that occurs when one has been standing for a while or abruptly changes from a sitting to standing position.
  • Heart disease can lead to fainting when heart defects cause outflow obstruction and prevent blood from flowing where it's needed.

Other causes of fainting include:

  • Anemia
  • Dehydration
  • Head injury
  • Heart inflammation
  • Holding breath
  • Inner ear problems
  • Irregular heartbeat
  • Low blood sugar
  • Pregnancy
  • Rapid heartbeat
  • Seizure
  • Stroke

Some fainting episodes can signal a serious disorder and should be evaluated by a physician:

  • Fainting after exercise
  • Syncope associated with palpitations or heart irregularities
  • Syncope associated with a family history of syncope or sudden death

Diagnosis and treatment

Most people who suffer from fainting episodes don't have heart disease or arrhythmias. To rule out any serious disease, a physician will take your blood pressure, as well as your sitting and standing heart rate.

If a more serious problem is expected, other tests may include:

People with syncope should be on a higher salt diet and drink plenty of fluids to maintain blood volume and prevent dehydration.

They should also be alert to signs of imminent fainting, including dizziness, sweaty palms and nausea.

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