Transient loss of consciousness—initial assessment, diagnosis, and specialist referral: summary of NICE guidanceBMJ 2010; 341 doi: http://dx.doi.org/10.1136/bmj.c4457 (Published 02 September 2010) Cite this as: BMJ 2010;341:c4457
- Maggie Westby, clinical effectiveness lead1,
- Ian Bullock, chief operating officer and guideline lead1,
- Paul N Cooper, consultant neurologist2,
- Sarah Davis, senior lecturer in health economics3
- on behalf of the Guideline Development Group
- 1National Clinical Guideline Centre, Royal College of Physicians of London, London NW1 4LE
- 2Greater Manchester Neurosciences Centre, Salford Royal Foundation Trust (Hope Hospital), Salford
- 3Health Economics and Decision Science, School of Health and Related Research, University of Sheffield, Sheffield S1 4DA
- Correspondence to: P N Cooper
Transient loss of consciousness is a spontaneous loss of consciousness with complete recovery, affecting a quarter to half of the population at some point in their lives.1 2 3 The condition has many possible causes, including cardiovascular disorders (ranging from cardiac arrhythmias to vasovagal syncope), epilepsy, and psychogenic attacks. Diagnosis is often inaccurate, inefficient, and delayed, and management varies considerably.1 Experience shows that the importance of obtaining information on the event itself and the need for early electrocardiography are not widely appreciated. This article summarises the most recent recommendations from the National Institute for Health and Clinical Excellence (NICE) on the management of transient loss of consciousness in people aged 16 and over.4
NICE recommendations are based on systematic reviews of best available evidence and explicit consideration of cost effectiveness. When minimal evidence is available, recommendations are based on the Guideline Development Group’s experience and opinion of what constitutes good practice. The recommendations emphasise elements of the diagnostic algorithm published in the Quick Reference Guide version of the NICE guidance, to which the reader should refer.4 Evidence levels for the recommendations are given in italic in square brackets
At any stage, including initial presentation, if the person has sustained an injury or has not made a full recovery of consciousness, or if transient loss of consciousness is secondary to a condition that needs immediate action, use clinical judgment to determine appropriate management and the urgency of treatment. [Based on the experience and opinion of the Guideline Development Group (GDG)]
Ask the person with suspected transient loss of consciousness, and any witnesses (try to contact these by phone if necessary), to describe what happened:
-Before the event (circumstances, posture, prodromal symptoms)
-During the event (appearance and colour; movement; any tongue biting or injury; and duration of transient loss of consciousness)
-During the recovery period (confusion, weakness down one side).
[Based on the experience and opinion of the GDG]
Use this information to confirm whether transient loss of consciousness has occurred. When in doubt assume it has. [Based on the experience and opinion of the GDG]
Assess and record:
-Details of any previous transient loss of consciousness
-Medical history and any family history of cardiac disease
-Lying and standing blood pressure if appropriate
-Other cardiovascular and neurological signs.
[Based on the experience and opinion of the GDG]
Electrocardiography, additional tests, and transfer of records
Record a 12 lead electrocardiogram for all patients with transient loss of consciousness, using automated interpretation. If automated interpretation is not available, the 12 lead electrocardiogram should be interpreted by someone competent in identifying certain abnormalities (box). If any abnormality listed in the box is identified in the electrocardiogram, treat it as a “red flag.” [Based on moderate, low and very low quality evidence from prospective and retrospective cohort studies and cross sectional studies and on the experience and opinion of the GDG]
Important abnormalities in a 12 lead electrocardiogram in patients with transient loss of consciousness
Atrial arrhythmia (sustained)
Inappropriate persistent bradycardia
Conduction abnormality (for example, complete right or left bundle branch block or any degree of heart block)
Left or right ventricular hypertrophy
Long QT interval (corrected >450 ms) and short QT interval (corrected <350 ms)
Pathological Q waves
Any ventricular arrhythmia (including ventricular extrasystoles)
Any abnormalities in ST segment or T wave, especially abnormal T wave inversion
If you suspect an underlying problem causing (or additional to) the transient loss of consciousness, conduct relevant examinations and investigations (for example, check blood glucose levels if hypoglycaemia is suspected, or haemoglobin levels if anaemia or bleeding is suspected). [Based on the experience and opinion of the GDG]
Record all information related to the transient loss of consciousness (include paramedics’ records). Obtain a witness description by telephone, if necessary. Give copies of the electrocardiogram and the patient report form to the receiving clinician when care is transferred, and to the person who had the transient loss of consciousness. [Based on the experience and opinion of the GDG]
Making a judgment based on initial assessment
Red flags: refer the patient within 24 hours for a specialist cardiovascular assessment by the most appropriate local service if the person has any of the following:
-Transient loss of consciousness during exertion
-New or unexplained breathlessness
-Family history of sudden cardiac death in people younger than 40 years and/or an inherited cardiac condition
-A heart murmur
-Any of the important electrocardiographic abnormalities listed (box).
[Based on evidence from low and moderate quality studies of diagnostic test accuracy, prospective cohort studies, and the experience and opinion of the GDG]
Consider referring within 24 hours anyone over 65 years who had transient loss of consciousness without prodromal symptoms. [Based on evidence from very low, low, and moderate quality studies of diagnostic test accuracy, prospective cohort studies, and the experience and opinion of the GDG]
If the patient has no features suggesting an alternative cause of transient loss of consciousness (note that brief seizure activity can occur during uncomplicated faints), diagnose uncomplicated faint or situational syncope, or suspect orthostatic hypotension when there are suggestive features as follows:
-Uncomplicated faint (the “three Ps”): posture (a faint may follow prolonged standing or the patient may have a history of similar episodes prevented by lying down); provoking factors (such as a medical procedure); prodromal symptoms (such as sweating before transient loss of consciousness) [Based on low and moderate quality evidence from prospective cohort studies, cross sectional studies, and retrospective cohort studies, and on the experience and opinion of the GDG]
-Situational syncope, in which syncope is clearly and consistently provoked by straining (such as with micturition), coughing, or swallowing [Based on the experience and opinion of the GDG]
-Orthostatic hypotension, in which the history is typical and lying and standing blood pressure (with repeated measurements while standing for three minutes) confirms orthostatic hypotension. [Based on low and very low quality evidence from a prospective cohort study and on the experience and opinion of the GDG]
Suspect epileptic seizures and refer people who present with one or more of the following for an assessment (within two weeks5) by a specialist in epilepsy:
-A bitten tongue
-Head turning to one side during transient loss of consciousness
-No memory of abnormal behaviour even though such behaviour has been witnessed by someone else before, during, or after transient loss of consciousness
-Prolonged jerking of limbs
-Confusion after transient loss of consciousness.
-Prodromal déjà vu, or jamais vu (a feeling that something is happening for the first time, despite knowing rationally that it has happened before)
[Based on low and very low quality evidence from a prospective cohort study and on the experience and opinion of the GDG]
Do not routinely use electroencephalography in the investigation of transient loss of consciousness.5 [Based on the NICE guidance on epilepsy and the experience and opinion of the GDG]
If a person has persistent transient loss of consciousness, consider psychogenic non-epileptic seizures if the nature of the episodes changes over time or the person has many different unexplained physical symptoms or unusually prolonged episodes. Psychogenic non-epileptic seizures can be difficult to distinguish from epilepsy; therefore refer for neurological assessment if suspected. [Based on low quality evidence from a prospective cohort study and on the experience and opinion of the GDG]
Transfer of care
If the diagnosis is uncomplicated faint or situational syncope and the presentation is not to the general practitioner, ask the general practitioner to arrange for electrocardiography to take place within three days (unless electrocardiography has already taken place). [Based on the experience and opinion of the GDG]
Refer all people with transient loss of consciousness for a specialist cardiovascular assessment by the most appropriate local service unless an uncomplicated faint, situational syncope, orthostatic hypotension, or suspected epilepsy is diagnosed. [Based on the experience and opinion of the GDG]
Specialist cardiovascular assessment and diagnosis
Conduct a specialist cardiovascular assessment and thereby assign a suspected cause of syncope (such as structural heart disease, cardiac arrhythmia, carotid sinus syncope, or neurally mediated syncope) or unexplained syncope. Offer further testing as directed in the recommendations or other tests as clinically appropriate. [Based on the experience and opinion of the GDG]
Offer exercise testing (unless contraindicated) when transient loss of consciousness has been experienced during (not after) exercise. [Based on very low quality evidence from a case-control study and on the experience and opinion of the GDG]
Do not offer a tilt test to people who have a diagnosis of vasovagal syncope on initial assessment, because tilt testing has a low predictive accuracy in this population. [Based on low quality evidence from case-control studies and on the experience and opinion of the GDG]
For people with suspected vasovagal syncope who experience recurrent episodes adversely affecting their quality of life, or are at high risk of injury, consider a tilt test only to assess whether the syncope is accompanied by a severe cardioinhibitory response (usually asystole). [Based on low quality evidence from a prospective case series and a non-randomised comparative study, and on the experience and opinion of the GDG]
For people with suspected carotid sinus syncope and for people with unexplained syncope who are aged 60 years or older, offer carotid sinus massage in a controlled environment as a first line investigation. [Based on low quality evidence from case-control studies and on the experience and opinion of the GDG]
For people with suspected cardiac arrhythmia as a cause of syncope, or with unexplained syncope (including those aged 60 years and older who have had a negative result for carotid sinus massage), offer ambulatory electrocardiography (and do not offer a tilt test before this procedure). Choose the type of ambulatory electrocardiography according to the frequency of the patient’s transient loss of consciousness:
-Several episodes a week: offer Holter monitoring (up to 48 hours), then if no further loss of consciousness occurs offer an external event recorder
- Episodes every one to two weeks: offer an external event recorder, then if necessary offer an implantable event recorder
- An episode less than once every two weeks: offer an implantable event recorder.
[Based on moderate and low quality evidence from randomised trials, low and very low quality evidence from case series, and the experience and opinion of the GDG]
For people with suspected structural heart disease, investigate appropriately (for example, with cardiac imaging). Other mechanisms for syncope are possible in this group, so investigate also for coexisting cardiac arrhythmia, and consider investigating for orthostatic hypotension (often caused or exacerbated by drug treatment) or for neurally mediated syncope. [Based the experience and opinion of the GDG]
Information on driving and health and safety at work
Advise all people who have had transient loss of consciousness that:
-If an uncomplicated faint or provoked situational syncope was diagnosed, they can drive provided the criteria of the Driver and Vehicle Licensing Agency are met.6
-If referred for a specialist assessment, they must not drive while waiting for their assessment, and they must discuss driving with the specialist
-There are implications for their health and safety at work.
[Based on the experience and opinion of the GDG]
Healthcare professionals often seem to lack the confidence to diagnose simple faints, and many patients are therefore thought to be subjected to inappropriate investigations, incorrect diagnoses, and unnecessary and potentially harmful treatments.7 To overcome this problem clinicians need to be more aware of the importance of information gathering and of the likely diagnoses, and be careful to tailor their management according to correct pathways of care. Initial assessment is critical and is dependent on careful history taking, particularly from a witness; this is an important topic for medical training.
For patients who have not had a simple uncomplicated faint, several potentially life threatening causes for transient loss of consciousness are possible, and these may need urgent, usually cardiological, assessment. Historically, cardiac services have tended to focus on ischaemic heart disease; new service models may improve access to timely investigations for people with blackouts.
Further information on the guidance
The causes of transient loss of consciousness vary, and people experiencing it may come under the care of a range of healthcare professionals, from general practitioners and ambulance staff to emergency department clinicians and specialists in cardiology or neurology. The lack of a clear pathway may contribute to misdiagnosis and inappropriate treatment. The guideline tackles these problems and provides recommendations for initial assessment, specialist referral, and further tests, so that a correct diagnosis can be reached quickly, efficiently, and cost effectively.
Determining the mechanism for transient loss of consciousness in an individual requires collection of evidence (from a detailed history, clinical assessment, and appropriate investigations) and interpretation of each piece of evidence in overall context with clinical reasoning. The guideline shows how this can best be achieved in the most cost effective way and gives indicators for diagnosis of some causes of transient loss of consciousness; however, it does not seek to replace clinical judgment or make recommendations on treatment.
The NICE guideline emphases the importance of obtaining an account of the event from the person who had transient loss of consciousness and from any witnesses and of using this information to make initial diagnoses.
Central to the guideline is the requirement that all people with transient loss of consciousness should have 12 lead electrocardiography, preferably using an automated machine. In line with the epilepsy guideline,5 we recommend against the routine use of electroencephalography in the investigation of transient loss of consciousness.
Further investigations focus particularly on the use of ambulatory electrocardiography devices, with the type of device selected being dependent on the frequency of previous episodes of transient loss of consciousness, thereby moving away from the often indiscriminate use of Holter monitors.
The guideline was developed using current NICE guideline methodology (www.nice.org.uk/aboutnice/howwework/developingniceclinicalguidelines/developing_nice_clinical_guidelines.jsp). This involved systematic literature searching and critically appraising and summarising the clinical and cost effectiveness evidence. A multidisciplinary guideline development group (GDG) comprising healthcare professionals from primary and secondary care, including emergency department clinicians, and patient representatives discussed the evidence and formulated the clinical recommendations. The supporting technical team included those with specific expertise in literature search techniques, systematic evidence review, health economics, and project management.
Health economic evidence was considered during the process of making guideline recommendations to ensure a cost effective use of healthcare resources. This comprised a review of existing published economic analyses, which provided evidence on the costs and benefits (in terms of quality adjusted life years) of interventions. Health economic evidence was limited, so the GDG and health economist developed new economic evaluation models for tests in a specialist cardiovascular environment. These models are described in detail in the full guideline.
The guideline was subject to a web based, external consultation from stakeholders. This drew 356 submitted comments, each of which was considered by the GDG for its validity and usefulness, and where deemed appropriate, the guideline was modified in the light of these.
Four versions of the guideline have been developed by NICE: the full version which includes the evidence reviews and the recommendations; the “NICE guideline,” which summarises the recommendations; the “quick reference guide,” which is an algorithm based version for healthcare professionals; and a version for patients and carers known as “understanding NICE guidance”. All these versions are available from the NICE website (http://guidance.nice.org.uk/CG109).
The following research recommendations were identified as high priority and are expected to lead to improved NICE guidance and patient care in the future:
Does providing people who have experienced transient loss of consciousness and their family or carers with information on the importance of witnessed accounts reduce the time to correct diagnosis and prevent inappropriate referrals?
Does using automated interpretation of electrocardiograms improve the accuracy of diagnosis among those who experience transient loss of consciousness compared with expert interpretation, and what is the overall effect on patient outcomes, including outcomes in patients with inherited long QT syndromes?
Does a serial assessment approach (repeated electrocardiography or repeated observations of vital signs) improve diagnosis of high risk cardiac arrhythmias when compared with a single assessment approach in people with transient loss of consciousness in any setting?
In people who are considered on the basis of clinical history and examination to have had an uncomplicated faint, what is the additional clinical effectiveness and cost effectiveness of 12 lead electrocardiography?
Under what circumstances is the implantable cardiac event recorder the investigation of choice for transient loss of consciousness in people in whom a cardiac cause is suspected?
Cite this as: BMJ 2010;341:c4457
This is one of a series of BMJ summaries of new guidelines based on the best available evidence; they highlight important recommendations for clinical practice, especially where uncertainty or controversy exists.
The members of the Guideline Development Group are Paul N Cooper (chair), Robin Beal, Mary Braine, Ian Bullock, Sarah Davis, Julie Fear, Melesina Goodwin, Richard Grünewald, Paddy Jelen, Fiona Jewkes, John Pawelec, Sanjiv Petkar, David Pitcher, Alison Pottle, Greg Rogers, Garry Swann, and Maggie Westby. Additional members from the National Clinical Guideline Centre are Paul Miller, Emma Nawrocki, and Nancy Turnbull.
Contributors: MW wrote the first draft. All authors reviewed the draft article critically for important intellectual content and approved the final version to be published. All authors are guarantors of this article.
Funding: The National Clinical Guideline Centre was commissioned and funded by the National Institute for Health and Clinical Excellence (NICE) to write this summary.
Competing interests: All authors have completed the Unified Competing Interest form at www.icmje.org./coi_disclosure.pdf (available on request from the corresponding author) and declare that (1) MW, IB and SD have no financial support for the submitted work from anyone other than their employer. PNC received an honorarium for chairing the Guideline Development Group; (2) PNC has supervised a research fellow who received funding from Medtronic; PNC has received travel expenses from Medtronic to attend an academic meeting. All other authors have no relationships with any companies that might have an interest in the submitted work in the previous 3 years; (3) All authors’ spouses, partners or children have no financial relationships that may be relevant to the submitted work; (4) All authors were members of the Guideline Development Group for the NICE guideline (PNC, the chair; MW, the systematic reviewer; SD the health economist; and IB the guideline lead).
Provenance and peer review: Commissioned; not externally peer reviewed.