Vasovagal syncope: symptoms, causes and treatment

Vasovagal syncope is an malaise that manifests itself as loss of consciousness for a short time. Most adults have ever experienced an episode of these, or, at least, the symptoms before it, called presyncope.

Most cases of vasovagal syncope are benign. Only a small proportion of these correspond to manifestations of some serious disorder. It is estimated that only 3% of this type of syncopes refer to medical consultation and only 1% lead to hospitalization.

Most often, after a vasovagal syncope, there is no consequence, except the effects of the fall. But nevertheless, some people suffer this type of episodes repeatedly, without there being a disease that explains them. In those cases, the quality of life is significantly affected.

What is vasovagal syncope

Vasovagal syncope is what we commonly know as fainting. It is defined as a brief, sudden and sudden loss of consciousness. This implies inability to stand up and loss of postural tone. Recovery occurs spontaneously.

The mechanism of vasovagal syncope is activated when the vagus nerve is stimulated by some trigger. This leads to a reduction in heart rate. and the blood vessels dilate, by action of the parasympathetic system. Under these conditions, a smaller amount of blood reaches the brain and syncope, or fainting, occurs.

Syncopes have been classified according to their duration. From that point of view, there are three types:

  • Light or presyncope, when there is no loss of consciousness in a strict sense, because what is experienced is a strong dizziness.
  • Moderate, which is a faint for a few seconds.
  • Severe, which lasts between 10 and 15 seconds and can lead to a seizure.


Vasovagal syncope corresponds to 75% of the total syncope cases. Most of the time they take place in healthy patients. Almost all of them have normal blood pressure, although a small group has a condition called orthostatic hypotension.

The symptoms that usually precede this type of syncopes are, among others:

  • Yawning
  • Weakness.
  • Hot.
  • Anxiety and hyperventilation.
  • Dizziness.
  • Vertigo.
  • Sickness.
  • Pallor.
  • Palpitations
  • Decrease of the visual field.
  • Ringing or feeling of plugging in the ears.
  • Trouble breathing and imminent feeling faint.

These previous symptoms do not always occur, but sometimes the loss of consciousness is sudden. During fainting, it is common for paleness, cold skin, great sweating and dilated pupils. After a moment of mental confusion and disorientation, consciousness gradually recovers. In some cases, there is fecal or urinary incontinence during fainting.

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Science has not completely deciphered the causes of vasovagal syncope. It is known that, during the episode, blood is concentrated in the legs, which leads to lower blood pressure and fainting, due to lack of blood flow to the brain.

The factors that influence this to happen are, among others:

  • Stay a long time standing.
  • Exposure to a source of heat for a long time.
  • Undergo a blood draw or see blood.
  • Make a great effort.
  • Hungry.
  • Shortness of breath
  • Altitude change
  • Strong odors

As well it is very common that the syncope is due to sudden changes in position or emotional stress. In the same way, in some cases the trigger is alcohol consumption, lack of salt in the diet or allergy to some medications.

Read also: How to act against fainting

Available treatments

When vasovagal syncope occurs in isolation, it generally receives no more treatment than immediate recovery after fainting. The most appropriate thing is to put the person to bed and lift his legs, so that the circulation returns to flow normally.

In cases of recurrent syncopes, it is best to consult the doctor, who will probably perform a stress test and / or a tilt test. Starting from this, recommend a pharmacological treatment or suggest lifestyle changes To avoid new episodes.

In some cases, for example, it is necessary to use compression stockings to decrease the accumulation of blood in the legs.