Syncope

What is syncope?

Syncope is the medical word for fainting or passing out. It happens when your brain briefly doesn't get enough blood, causing you to lose consciousness for a few seconds or minutes before you come round on your own.

What are the common causes of syncope?

Most fainting happens because of a temporary drop in blood pressure or heart rate, rather than a serious underlying illness. Common causes include:

• standing for a long time, especially somewhere hot or crowded
• sudden strong emotion, pain, or the sight of blood or needles
• dehydration, or not having eaten for a while
• standing up quickly after sitting or lying down
• straining, such as coughing hard, passing urine, or having a bowel movement
• certain medicines, including some blood pressure tablets and decongestants
• drinking too much alcohol or caffeine.

Less often, syncope is linked to a more serious underlying problem, such as:

• an abnormal heart rhythm, or a problem with a heart valve
• a tear in a major blood vessel near the heart (aortic dissection), which is rare but life-threatening
• a neurological condition, such as a seizure, stroke, or mini-stroke (transient ischaemic attack, TIA)
• a condition affecting blood pressure control on standing, such as postural orthostatic tachycardia syndrome (POTS).

Are there different types of syncope?

Yes. Doctors usually group syncope into a few main types, based on what causes it:

• Reflex (vasovagal) syncope, the most common type, where your body overreacts to a trigger such as standing too long, pain, or emotional stress, causing your heart rate and blood pressure to drop
• Situational syncope, a type of reflex syncope triggered by specific actions such as coughing hard, passing urine, or straining
• Orthostatic (postural) syncope, caused by a sudden drop in blood pressure when you change position, such as standing up quickly
• Cardiac syncope, caused by a heart or blood vessel problem, such as an abnormal heart rhythm or valve disease
• Neurological syncope, linked to a condition affecting the brain or nerves, such as a seizure, stroke, or TIA
• Postural orthostatic tachycardia syndrome (POTS), where your heart rate rises sharply and your blood pressure struggles to stay steady when you stand up.

Reflex (vasovagal) syncope is by far the most common type, making up around half of all cases. Cardiac syncope is much less common, at around 1 in 10 cases, but it's taken particularly seriously, since it can point to an underlying heart condition that needs treatment.

How is syncope diagnosed?

A doctor will ask detailed questions about what happened before, during, and after you fainted, including your position at the time, any warning signs you noticed, and your medical history and medicines. They'll also check your blood pressure and heart rate while you're lying down, sitting, and standing.

In many cases, this is enough to work out the likely cause. If not, you may need further tests, such as:

• an electrocardiogram (ECG) to check your heart's electrical activity
• blood tests to check for anaemia or other changes
• a tilt table test, where you're moved from lying down to standing while your heart rate and blood pressure are monitored
• a heart monitor worn for several days or weeks to catch any abnormal rhythms
• an echocardiogram (an ultrasound scan of your heart), or a CT or MRI scan if a brain-related cause is suspected.

How is syncope treated?

Treatment depends entirely on what's causing your syncope, and the aim is to stop it happening again. Simple measures that often help include:

• staying well hydrated and eating regularly, including a little more salt if a doctor advises it
• avoiding known triggers, such as standing for long periods, hot rooms, or alcohol
• standing up slowly from sitting or lying down
• wearing compression stockings to help blood flow back to your heart
• raising the head of your bed slightly.

If a specific cause is found, treatment may include medicines to support your blood pressure or heart rhythm, or, less commonly, a pacemaker or similar device to correct a heart rhythm problem. Treatment for a serious cause, such as a heart or neurological condition, will be tailored to that diagnosis.

When should I see a doctor?

See a doctor after any fainting episode, even if you feel fine afterwards, since it's important to rule out a more serious cause. Avoid driving until you've been checked, since some causes of syncope can happen again without warning.

Get medical help urgently if:

• you had chest pain, a racing or irregular heartbeat, or shortness of breath before or after fainting
• you fainted without any warning signs, or while lying down
• you were injured in a fall, or fainted during exercise
• you have a history of heart disease
• fainting episodes keeps happening.