Blackouts (also called fainting or syncope), are due to temporary loss of consciousness. These are often simple faints but can be due to problems with the heart (causing a reduced blood supply to the brain) or due to a problem with the brain itself.
causing blackouts include heart rhythm disturbance (either slow or fast heart rhythms) and heart valve malfunction (eg aortic stenosis).
often required after a blackout are: ECG, echocardiogram (ultrasound scan of the heart) and 24 hour heart rhythm monitoring (achieved by wearing a small monitor for a day).
If your GP thinks the blackouts are due to a problem with the brain, you will be referred to a neurologist. Sometimes it is unclear what the likely cause is and you may be referred to both a neurologist and cardiologist.