Terms used in this guideline

This section defines terms that have been used in a particular way for this guideline. For other definitions, see the NICE glossary and the Think Local, Act Personal Care and Support Jargon Buster. See also NICE's guideline on epilepsies in children, young people and adults for a more detailed glossary of terms related to epilepsy.

12-lead electrocardiogram (ECG)

Recording of the heart's electrical signals obtained by attaching electrodes in ten standard positions on the limbs and the surface of the chest. This provides a display of the electrical activity of the heart viewed from 12 different directions.


An abnormal heart rhythm.


Sustained absence of the heart's electrical activity.


Sudden and spontaneous transient loss of consciousness (TLoC) with complete recovery. In this context, complete recovery would involve full recovery of consciousness without any residual neurological deficit.


Slow heart rate (irrespective of rhythm), conventionally defined as less than 60 beats per minute.

Brugada syndrome

An inherited ion channel disorder characterised by abnormal ST segment elevation in leads V1 to V3 on ECG. This predisposes to ventricular arrhythmia and sudden cardiac death, and may present with syncope.

Cardiac arrhythmic syncope

Syncope caused by a sudden abnormality of heart rhythm, which may be a bradyarrhythmia (abnormal rhythm with a slow heart rate) or a tachyarrhythmia (abnormal rhythm with a fast heart rate).

Carotid sinus massage

A procedure in which the carotid sinus is stimulated (by firm massage with a thumb during continuous ECG and blood pressure monitoring in both supine and upright positions) to investigate suspected or possible carotid sinus syncope.

Carotid sinus syncope

A form of neurally mediated syncope in which pressure on 1 or other carotid artery causes syncope.

Convulsive syncope

Loss of consciousness caused by transient insufficiency of blood supply to the brain accompanied by jerky or posturing movements, generally involving the limbs.

Déjà vu

An intense sensation that what is happening for the first time has already occurred previously. This is common particularly in adolescence, but may be a manifestation of a partial seizure (rather than occurring immediately before an epileptic seizure).


Immediate action within 24 hours.

Exercise-induced syncope

Syncope induced by exercise.

External event recorder

A small portable recorder that is capable of monitoring and storing ECG recordings from electrodes on the skin. The device records the heart's rhythm during symptoms (including syncope) that occur intermittently. Excludes event recorders that do not perform continuous ECG monitoring (and therefore are not capable of documenting cardiac rhythm at the moment of TLoC).


Episode of TLoC due to vasovagal syncope. Fainting is a temporary loss of consciousness due to a drop in blood flow to the brain. The episode is brief and is followed by rapid and complete recovery.

Holter monitor/recorder

A small portable recorder that is capable of continuous ECG recording from electrodes on the skin, usually used over a 24- to 72-hour period.

Ictal arrhythmia

A disturbance of normal heart rhythm occurring during a seizure.

Implantable event recorder

Small implantable device capable of monitoring and storing ECG recordings of the heart's rhythm. It is also known as an implantable or insertable loop recorder.

Jamais vu

A feeling of lack of familiarity, that what should be familiar is happening for the first time; it is usually abnormal, it doesn't commonly occur in healthy people.

Long QT syndromes

Inherited conditions characterised by prolongation of a specific portion of the ECG. This predisposes to ventricular arrhythmia and sudden cardiac death, and may present with syncope.

Micturition syncope

A form of neurally mediated syncope provoked by straining while passing urine while standing.

Neurally mediated syncope

Sometimes called 'reflex syncope'. TLoC due to a reflex hypotensive response and/or reflex bradycardic response to a number of causes; this category includes vasovagal syncope, carotid sinus syncope, and situational syncope.

Postural hypotension

Condition in which a marked fall in blood pressure is provoked by a change in posture from lying to sitting, or from lying or sitting to standing. This may cause light-headedness (dizziness), a fall, or TLoC.

Post-ictal confusion

An abnormal state that follows an attack, usually referring to a disturbed condition after an epileptic seizure.


A sensation of impending fainting or loss of consciousness.


Symptoms which precede the episode, usually considered to be more prominent than an aura, which is usually very brief.


A psychogenic non-epileptic attack characterised by loss of muscle tone and having the appearance of a faint.

Psychogenic non-epileptic seizures (PNES)

Episodes of altered movement, sensation or experience, similar to epilepsy but caused by a psychological process and not associated with abnormal electrical discharges in the brain.

Red flags

For this guideline, the term 'red flags' indicates that the person is considered to be at high risk of a serious adverse event and should be referred for urgent specialist assessment.

Short QT syndrome

Inherited condition characterised by a specific portion of the ECG being of abnormally short duration. This predisposes to ventricular arrhythmia and sudden cardiac death, and may present with syncope.

Situational syncope

A form of neurally mediated syncope occurring in certain specific situations (for example, cough syncope, micturition syncope, or swallowing syncope).


A healthcare professional who has expert knowledge of, and skills in, a particular clinical area, especially 1 who is certified by a higher medical educational organisation.

Structural heart disease

Any disease of the heart in which the structural components of the heart are abnormal. This encompasses heart muscle disease, valve disease and congenital heart disease.


Fast heart rate (irrespective of rhythm), conventionally defined as greater than 100 beats per minute.

Tilt test

Test in which a patient is exposed to passive head-up tilt, during which they have beat-to-beat measurement of heart rate and blood pressure, to try to demonstrate whether or not they have a provocable tendency to vasovagal syncope.

Transient loss of consciousness (TLoC)

Preferred term for a blackout.

Vasovagal syncope

A form of neurally mediated syncope. This is often, but not always, triggered by circumstances such as pain, prolonged standing (especially in a warm environment), or emotional stress. This commonly presents as an identifiable 'uncomplicated faint' but can present as sudden unprovoked syncope.

Ventricular fibrillation

Chaotic electrical activity in the heart's ventricles, causing loss of pumping action and resulting in cardiac arrest. If not corrected immediately, this will lead to death.

Ventricular tachycardia

Tachycardia arising from the heart's ventricular muscle. This can in some people cause syncope or cardiac arrest and sudden death.

  • National Institute for Health and Care Excellence (NICE)