Syncope
Syncope is a sudden, temporary loss of consciousness, also known as fainting or ‘passing out’, which is caused by a reduction in the blood flow to the brain.
What are the causes of syncope?
Syncope can be due to a number of different causes. The most common cause is vasovagal (also known as reflex neurocardiogenic) syncope, where in response to a certain stimulus there is a drop in heart rate and a pooling of blood in the legs, leading to a lack of blood flow to the brain.
There are a number of common triggers for vasovagal syncope, including prolonged standing (especially in a hot environment), severe pain, emotional distress, the sight of blood, severe coughing, urinating or opening the bowels.
Other less common causes of syncope include:
- arrhythmias (abnormal heart rhythms);
- orthostatic hypotension (a drop in blood pressure when standing), which may in turn be due to a number of causes;
- structural heart disease; and
- some neurological, metabolic and psychiatric disorders.
How is syncope evaluated?
Your doctor will take a detailed history from you and perform a physical examination to try to determine the cause of the syncope.
An electrocardiogram (ECG), which records the electrical impulses given off by your heart, and blood tests will also commonly be performed.
If the cause of the fainting is still not apparent after the initial assessment, an echocardiogram (ultrasound of the heart) will usually be performed, and additional investigations may be required.
What is the treatment for syncope?
Treatment for syncope depends on the underlying cause.
People with vasovagal syncope should watch for warning signs of fainting — such as light-headedness, sweating, nausea, ringing in the ears — and try to lie down (preferably with legs elevated), or if this is not possible, to sit down at the earliest warning signs.
Other measures that can help to temporarily increase blood pressure and avoid collapse include squeezing the calf muscles or buttocks together.
They should also avoid becoming dehydrated and generally try to avoid situations likely to trigger fainting. Occasionally, other treatments such as medication may be required for vasovagal syncope.
If the syncope is due to another condition — such as underlying heart disease — specific treatment for that condition will be arranged. Your doctor will advise you as to the appropriate treatment in your case.
Last Reviewed: 16 November 2007
