STARS Patient Information

Reflex Syncope (Neurally Mediated Syncope/Vasovagal Syncope)

SYNCOPE (sin-co-pee) is a medical term for a blackout that is caused by a sudden lack of blood supply to the brain. Reflex syncope is one of the most common forms of syncope. Sometimes called neurally mediated syncope, or vasovagal syncope (VVS), it is a transient condition resulting from intermittent dysfunction of the autonomic nervous system, which regulates blood pressure and heart rate.

Autonomic sympathetic nerves that constrict blood vessels and maintain blood pressure, in reflex syncope withdraw their input, and blood pressure falls. The vagus nerve which directly controls heart rate, can increase activity and cause the heart rate to fall (bradycardia). Both blood pressure and heart rate, (sometimes one but not the other) can fall to very low levels thus reducing blood supply, oxygen and essential nutrients to the brain and other vital organs.

This can cause dizziness, visual disturbances and blackouts. These symptoms are most likely to be a problem when upright (due to gravity further lowering blood pressure), but other factors such as food, heat, exercise, sight of blood and emotional stress can bring it on. Syncope affects 50% of the population but only 1% is affected by epilepsy. It is very important to make sure that syncope and epilepsy are distinguished from each other; a blackout is too often assumed to be due to epilepsy. If you have any doubt, then please look at the STARS Blackouts Checklist which has been written specifi cally to help doctors and patients reach the correct diagnosis for an unexplained loss of consciousness.


Symptoms vary from patient to patient and from one faint to another. The most common symptoms are light headedness, dizziness, and nausea. Some people will feel very hot and clammy, sweaty and complain of visual and hearing disturbances. Many individuals become very pale.


A good description by a witness, keeping a diary of events and consulting a doctor who is fully aware of the condition and takes a detailed history will lead to a correct diagnosis. Every patient who suff ers a blackout should be given a 12-lead ECG.

  • 12-lead electrocardiogram (ECG) is used to analyse the heart rhythm.

The following tests are sometimes also used to help doctors make a diagnosis:


  • A heart rhythm monitor records heart rhythms whilst away from hospital.
  • A tilt table test is an autonomic test used to induce an attack whilst connected to heart and blood pressure monitors. Ideally, this test should be performed with other autonomic tests, as these aid diagnosis and also help in treatment, especially in advising on non-drug measures to prevent or reduce blackouts.
  • An implantable loop recorder (ILR) is used to monitor heart rhythms for months at a time if the episodes are less frequent than every 30 days. The device can remain in place for up to three years.
  • An electroencephalogram (EEG) is used to analyse brain activity.

Immediate action in the event of a syncope attack:

The second you feel your usual symptoms coming on:
1. If symptoms are mild or you are unable to sit or lie down, cross your ankles and tense your calf muscles tightly. Combine this movement with buttock clenching to make effects more pronounced (this will help to get the blood pumping around your body and increase your blood pressure so relieving symptoms).
2. If you are able, sit down IMMEDIATELY or, if possible LIE DOWN FLAT AND PUT YOUR LEGS IN THE AIR - for example against a wall or propped up on pillows, and if you can it is preferable to do a cycling movement with your legs.
3. SQUAT if you are unable to lie down.
4. Don’t try to fi ght your symptoms; you are not stronger than your blood pressure, and it will win!
5. GET UP CAUTIOUSLY when you feel well again. Slowly sit up and gradually stand up.

If symptoms continue, promptly repeat immediate action steps.

Get in touch for more help and information

+44 (0) 1789 867


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