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A significant number of people will experience a blackout in their lifetime. In most cases the blackout will not cause any serious harm and will never recur.  In a small number of cases the blackout might be caused by a serious medical cause  and patients may need specific treatment.

What is a blackout

A blackout is a transient loss of consciousness for a few seconds or minutes.  There are a large number of causes of blackouts but when it is thought to have a cardiac cause it is called cardiac syncope.

The causes of blackouts

There are a large number of causes of blackout from a simple faint (neurally mediated vasovagal syncope)  through to other more serious cardiac causes such as epilepsy, postural hypotension and psychogenic causes.  Cardiac syncope is caused by a sudden lack of blood supply to the brain because of a low BP or a problem with the heart rhythm.

Do falls represent blackouts

There are a large number of causes of falls including mechanical causes, postural instability, low BP and a proportion of elderly people with unexplained falls may be caused by blackouts.

When to seek medical attention

Most patients with blackouts should see their GP to discuss the blackout. Many patients will have a benign cause of blackout such as a simple faint.  However,  a proportion of patients with high risk features will then need to be referred for specialist input for example by a neurologist or cardiologist.  

What tests would be required

All patients with blackouts who see a specialist should have a 12 lead ECG recording, other tests which may be required include an echocardiogram, tilt-table test, holter monitor, some patients may require an Implantable loop recorder (ILR) as well as other specialist tests including a cardiac MRI.  If the blackouts are thought to be neurological in origin then a MRI of the brain and an EEG may be required.

Implantable loop recorder

This is a device inserted under the skin in the chest wall on the left hand side. It is inserted under local anaesthetic as a day case procedure.

The device is designed to monitor your heart rhythm continuously and is useful for patients who are having syncope to diagnose problems with their heart rhythm which might cause them to blackout.


(Image courtesy of Medtronic PLC)

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