- This guideline covers assessment, diagnosis and referral for people over 16 who have had a transient loss of consciousness (TLoC; also called a blackout). It aims to improve care for people with TLoC by specifying the most effective assessments and recommending when to refer to a specialist.
- This guideline is the basis of QS71.
Contents included in this summary
1.1 Initial assessment
1.1.1 Gathering information about the event and initial decision-making
184.108.40.206 If the person with suspected transient loss of consciousness (TLoC) has sustained an injury or they have not made a full recovery of consciousness, use clinical judgement to determine appropriate management and the urgency of treatment.
220.127.116.11 Ask the person who has had the suspected TLoC, and any witnesses, to describe what happened before, during and after the event. Try to contact by telephone witnesses who are not present. Record details about:
- circumstances of the event
- person’s posture immediately before loss of consciousness
- prodromal symptoms (such as sweating or feeling warm/hot)
- appearance (for example, whether eyes were open or shut) and colour of the person during the event
- presence or absence of movement during the event (for example, limb-jerking and its duration)
- any tongue-biting (record whether the side or the tip of the tongue was bitten)
- injury occurring during the event (record site and severity)
- duration of the event (onset to regaining consciousness)
- presence or absence of confusion during the recovery period
- weakness down one side during the recovery period.
18.104.22.168 When recording a description of the suspected TLoC from the patient or a witness, take care to ensure that their communication and other needs are taken into account. This is particularly important when communicating with a child or young person, or person with special communication needs.
Determining whether the person had TLoC
22.214.171.124 Use information gathered from all accounts of the suspected TLoC (see recommendation 126.96.36.199) to confirm whether or not TLoC has occurred. If this is uncertain it should be assumed that they had TLoC until proven otherwise. But, if the person did not have TLoC, instigate suitable management (for example, if the person is determined to have had a fall, rather than TLoC, see the NICE guideline on falls in older people: assessing risk and prevention).
1.1.2 Obtaining patient history, physical examination and tests
188.8.131.52 Assess and record:
- details of any previous TLoC, including number and frequency
- the person’s medical history and any family history of cardiac disease (for example, personal history of heart disease and family history of sudden cardiac death)
- current medication that may have contributed to TLoC (for example, diuretics)
- vital signs (for example, pulse rate, respiratory rate and temperature) – repeat if clinically indicated
- lying and standing blood pressure if clinically appropriate
- other cardiovascular and neurological signs.
184.108.40.206 Record a 12-lead electrocardiogram (ECG) using automated interpretation. Treat as a red flag (see recommendation 220.127.116.11) if any of the following abnormalities are reported on the ECG printout:
- conduction abnormality (for example, complete right or left bundle branch block or any degree of heart block)
- evidence of a long or short QT interval, or
- any ST segment or T wave abnormalities.
18.104.22.168 If a 12-lead ECG with automated interpretation is not available, take a manual 12-lead ECG reading and have this reviewed by a healthcare professional trained and competent in identifying the following abnormalities.
- Inappropriate persistent bradycardia.
- Any ventricular arrhythmia (including ventricular ectopic beats).
- Long QT (corrected QT > 450 ms) and short QT (corrected QT < 350 ms) intervals.
- Brugada syndrome.
- Ventricular pre-excitation (part of Wolff-Parkinson-White syndrome).
- Left or right ventricular hypertrophy.
- Abnormal T wave inversion.
- Pathological Q waves.
- Atrial arrhythmia (sustained).
- Paced rhythm.
22.214.171.124 If during the initial assessment, there is suspicion of an underlying problem causing TLoC, or additional to TLoC, carry out relevant examinations and investigations (for example, check blood glucose levels if diabetic hypoglycaemia is suspected, or haemoglobin levels if anaemia or bleeding is suspected; see also recommendation 126.96.36.199 for information about the use of electroencephalogram [EEG]).
1.1.3 Recording the event information and transfer of records
188.8.131.52 Record carefully the information obtained from all accounts of the TLoC. Include paramedic records with this information. Give copies of the ECG record and the patient report form to the receiving clinician when care is transferred, and to the person who had the TLoC.
1.1.4 Making a judgement based on initial assessment
Red flags: people requiring urgent assessment and treatment
184.108.40.206 If TLoC is secondary to a condition that requires immediate action, use clinical judgement to determine appropriate management and the urgency of treatment.
220.127.116.11 Refer urgently for cardiovascular assessment, with the referral reviewed and prioritised by an appropriate specialist within 24 hours, anyone with TLoC who also has any of the following.
- An ECG abnormality (see recommendations 18.104.22.168 and 22.214.171.124).
- Heart failure (history or physical signs).
- TLoC during exertion.
- Family history of sudden cardiac death in people aged younger than 40 years and/or an inherited cardiac condition.
- New or unexplained breathlessness.
- A heart murmur.
Consider referring within 24 hours for cardiovascular assessment, as above, anyone aged older than 65 years who has experienced TLoC without prodromal symptoms.
No further immediate management required
126.96.36.199 Diagnose uncomplicated faint (uncomplicated vasovagal syncope) on the basis of the initial assessment when:
- there are no features that suggest an alternative diagnosis (note that brief seizure activity can occur during uncomplicated faints and is not necessarily diagnostic of epilepsy) and
- there are features suggestive of uncomplicated faint (the 3 ‘P’s) such as:
- Posture – prolonged standing, or similar episodes that have been prevented by lying down
- Provoking factors (such as pain or a medical procedure)
- Prodromal symptoms (such as sweating or feeling warm/hot before TLoC).
188.8.131.52 Diagnose situational syncope on the basis of the initial assessment when:
- there are no features from the initial assessment that suggest an alternative diagnosis and
- syncope is clearly and consistently provoked by straining during micturition (usually while standing) or by coughing or swallowing.
184.108.40.206 If a diagnosis of uncomplicated faint or situational syncope is made, and there is nothing in the initial assessment to raise clinical or social concern, no further immediate management is required. If the presentation is not to the GP, the healthcare professional should:
- advise the person to take a copy of the patient report form and the ECG record to their GP
- inform the GP about the diagnosis, directly if possible; if an ECG has not been recorded, the GP should arrange an ECG (and its interpretation as described in recommendation 220.127.116.11) within 3 days.
Further immediate management required
18.104.22.168 If the person presents to the ambulance service, take them to the Emergency Department unless a diagnosis of an uncomplicated faint or situational syncope is clear.
1.2 Further assessment and referral
1.2.1 Suspected orthostatic hypotension
22.214.171.124 Suspect orthostatic hypotension on the basis of the initial assessment when:
- there are no features suggesting an alternative diagnosis and
- the history is typical.
If these criteria are met, measure lying and standing blood pressure (with repeated measurements while standing for 3 minutes). If clinical measurements do not confirm orthostatic hypotension despite a suggestive history, refer the person for further specialist cardiovascular assessment.
If orthostatic hypotension is confirmed, consider likely causes, including drug therapy, and manage appropriately (for example, see the NICE guideline on falls in older people: assessing risk and prevention).
1.2.2 Suspected epilepsy
126.96.36.199 Refer people who present with one or more of the following features (that is, features that are strongly suggestive of epileptic seizures) for an assessment by a specialist in epilepsy; the person should be seen by the specialist within 2 weeks (see the NICE guideline on epilepsies: diagnosis and management).
- A bitten tongue.
- Head-turning to one side during TLoC.
- No memory of abnormal behaviour that was witnessed before, during or after TLoC by someone else.
- Unusual posturing.
- Prolonged limb-jerking (note that brief seizure-like activity can often occur during uncomplicated faints).
- Confusion following the event.
- Prodromal déjà vu, or jamais vu (see glossary, appendix C of the full guideline).
Consider that the episode may not be related to epilepsy if any of the following features are present.
- Prodromal symptoms that on other occasions have been abolished by sitting or lying down.
- Sweating before the episode.
- Prolonged standing that appeared to precipitate the TLoC.
- Pallor during the episode.
Do not routinely use EEG in the investigation of TLoC (see the NICE guideline on epilepsies: diagnosis and management).
1.2.3 Referral for specialist cardiovascular assessment
188.8.131.52 Refer all people with TLoC (apart from the exceptions below) for a specialist cardiovascular assessment by the most appropriate local service. Exceptions are:
- people with a firm diagnosis, after the initial assessment, of:
- uncomplicated faint
- situational syncope
- orthostatic hypotension
- people whose presentation is strongly suggestive of epileptic seizures.
1.3 Specialist cardiovascular assessment and diagnosis
1.3.1 Assessment and assignment to type of syncope
184.108.40.206 Carry out a specialist cardiovascular assessment as follows.
- Reassess the person’s:
- detailed history of TLoC including any previous events
- medical history and any family history of cardiac disease or an inherited cardiac condition
- drug therapy at the time of TLoC and any subsequent changes.
- Conduct a clinical examination, including full cardiovascular examination and, if clinically appropriate, measurement of lying and standing blood pressure.
- Repeat 12-lead ECG and obtain and examine previous ECG recordings.
On the basis of this assessment, assign the person to one of the following suspected causes of syncope.
- Suspected structural heart disease.
- Suspected cardiac arrhythmic.
- Suspected neurally mediated.
Offer further testing as directed by recommendations 220.127.116.11 to 18.104.22.168 or other tests as clinically appropriate.
22.214.171.124 For people with suspected structural heart disease, investigate appropriately (for example, cardiac imaging). Because other mechanisms for syncope are possible in this group, also consider investigating for a cardiac arrhythmic cause (as described in recommendation 126.96.36.199), and for orthostatic hypotension (often caused/exacerbated by drug therapy – see recommendation 188.8.131.52) or for neurally mediated syncope (see recommendations 184.108.40.206 and 220.127.116.11).
1.3.2 Diagnostic tests for different types of syncope
18.104.22.168 Use the person’s history to distinguish people whose exercise-induced syncope occurred during exercise (when a cardiac arrhythmic cause is probable) from those whose syncope occurred shortly after stopping exercise (when a vasovagal cause is more likely).
22.214.171.124 For people who have experienced syncope during exercise, offer urgent (within 7 days) exercise testing, unless there is a possible contraindication (such as suspected aortic stenosis or hypertrophic cardiomyopathy requiring initial assessment by imaging). Advise the person to refrain from exercise until informed otherwise following further assessment.
126.96.36.199 If the mechanism for exercise-induced syncope is identified by exercise testing, carry out further investigation or treatment as appropriate in each individual clinical context. Otherwise, carry out further investigations assuming a suspected cardiac arrhythmic cause.
188.8.131.52 For people with a suspected cardiac arrhythmic cause of syncope, offer an ambulatory ECG and do not offer a tilt test as a first-line investigation. The type of ambulatory ECG offered should be chosen on the basis of the person’s history (and, in particular, frequency) of TLoC. For people who have:
- TLoC at least several times a week, offer Holter monitoring (up to 48 hours if necessary). If no further TLoC occurs during the monitoring period, offer an external event recorder that provides continuous recording with the facility for the patient to indicate when a symptomatic event has occurred.
- TLoC every 1–2 weeks, offer an external event recorder. If the person experiences further TLoC outside the period of external event recording, offer an implantable event recorder.
- TLoC infrequently (less than once every 2 weeks), offer an implantable event recorder. A Holter monitor should not usually be offered unless there is evidence of a conduction abnormality on the 12-lead ECG.
184.108.40.206 Do not offer a tilt test to people who have a diagnosis of vasovagal syncope on initial assessment.
220.127.116.11 For people with suspected vasovagal syncope with recurrent episodes of TLoC adversely affecting their quality of life, or representing a high risk of injury, consider a tilt test only to assess whether the syncope is accompanied by a severe cardioinhibitory response (usually asystole).
18.104.22.168 For people with suspected carotid sinus syncope and for people with unexplained syncope who are aged 60 years or older, offer carotid sinus massage as a first-line investigation. This should be conducted in a controlled environment, with ECG recording, and with resuscitation equipment available.
22.214.171.124 Diagnose carotid sinus syncope if carotid sinus massage reproduces syncope due to marked bradycardia/asystole and/or marked hypotension. Do not diagnose carotid sinus syncope if carotid sinus massage causes asymptomatic transient bradycardia or hypotension (see recommendation 126.96.36.199).
188.8.131.52 For all people with unexplained syncope (including after negative carotid sinus massage test in those for whom this is appropriate), offer ambulatory ECG (see recommendation 184.108.40.206). Do not offer a tilt test before the ambulatory ECG.
220.127.116.11 When offering a person an implantable event recorder, provide one that has both patient-activated and automatic detection modes. Instruct the person and their family and/or carer how to operate the device. Advise the person that they should have prompt[A] follow-up (data interrogation of the device) after they have any further TLoC.
1.4 If the cause of TLoC remains uncertain
18.104.22.168 If a person has persistent TLoC, consider psychogenic non-epileptic seizures (PNES) or psychogenic pseudosyncope if, for example:
- the nature of the events changes over time
- there are multiple unexplained physical symptoms
- there are unusually prolonged events.
The distinction between epilepsy and non-epileptic seizures is complex; therefore refer for neurological assessment if either PNES or psychogenic pseudosyncope is suspected.
22.214.171.124 Advise people who have experienced TLoC to try to record any future events (for example, a video recording or a detailed witness account of the event), particularly if the diagnosis is unclear or taking a history is difficult.
126.96.36.199 If after further assessment the cause of TLoC remains uncertain or the person has not responded to treatment, consider other causes including the possibility that more than one mechanism may co-exist (for example, ictal arrhythmias).
1.5 Information for people with TLoC
1.5.1 General information
188.8.131.52 When communicating with the person who had TLoC, discuss the:
- possible causes of their TLoC
- benefits and risks of any tests they are offered
- results of tests they have had
- reasons for any further investigations they are offered
- nature and extent of uncertainty in the diagnosis.
184.108.40.206 Give advice about eligibility to drive when a person first presents with TLoC[B].
220.127.116.11 Advise all people who have experienced TLoC that they must not drive while waiting for a specialist assessment. Following specialist assessment, the healthcare professional should advise the person of their obligations regarding reporting the TLoC event to the Driver and Vehicle Licensing Agency (DVLA)[B].
1.5.3 Health and safety at work
18.104.22.168 Advise people who have experienced TLoC of the implications of their episode for health and safety at work and any action they must take to ensure the safety of themselves and that of other people[C].
1.5.4 Safety advice for people who have had TLoC
22.214.171.124 For people with an uncomplicated faint (uncomplicated vasovagal syncope) or situational syncope:
- explain the mechanisms causing their syncope
- advise on possible trigger events, and strategies for avoiding them. If the trigger events are unclear, advise people to keep a record of their symptoms, when they occur and what they were doing at the time, in order to understand what causes them to faint
- reassure them that their prognosis is good
- advise them to consult their GP if they experience further TLoC, particularly if this differs from their recent episode.
126.96.36.199 For people with orthostatic hypotension:
- explain the mechanisms causing their syncope
- discuss and review possible causes, especially drug therapy
- discuss the prognostic implications and treatment options available
- advise people what to do if they experience another TLoC.
188.8.131.52 Advise people waiting for a specialist cardiovascular assessment:
- what they should do if they have another event
- if appropriate, how they should modify their activity (for example, by avoiding physical exertion if relevant) and not to drive[B].
184.108.40.206 Offer advice to people waiting for specialist neurological assessment for their TLoC as recommended in the NICE guideline on epilepsies: diagnosis and management.
[A] The timing of the follow-up is dependent on the storage on the device and the condition of the person.
[B] Please refer to the DVLA for further information.
[C] Please refer to Health and Safety at Work etc Act 1974
NICE guidance is prepared for the National Health Service in England. All NICE guidance is subject to regular review and may be updated or withdrawn. NICE accepts no responsibility for the use of its content in this product/publication.