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Transient loss of consciousness 1: causes and impact of misdiagnosis

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This article outlines the various causes of blackouts and examines the consequences of misdiagnosis

Figures and tables can be seen in the attached print-friendly PDF file of the complete article in the ‘Files’ section of this page

Andrea Meyer, RGN,
is syncope nurse specialist, Imperial College Syncope Diagnostic Centre, St Mary’s Campus, London.

Meyer, A.
(2009) Transient loss of consciousness 1: causes and impact of misdiagnosis.Nursing Times;105: 8, 16-18.

Click here for PDFs of the articles and the Portfolio Pages corresponding to this unit

Part 1 of this two-part unit outlines the various possible causes of transient loss of consciousness (blackouts), the importance of accurate diagnosis and the impact of misdiagnosis. It also discusses the establishment of specialist clinics in order to help with diagnosis and management.

Click here for diagram: Effect of heart block on conduction of cardiac impulses

Learning objectives

  1. Know the possible underlying causes and prevalence of transient loss of consciousness.
  2. Understand the importance of correctly diagnosing patients presenting with T-LoC.

Causes of blackouts

Up to 50% of the general population will experience a blackout - or ‘transient loss of consciousness’ (T-LoC) - at some point during their lifetime (Fitzpatrick and Cooper, 2006; Petkar et al, 2005). These incidents account for approximately 1% of hospital admissions (Brignole et al, 2006).

There are a number of possible causes for a T-LoC. These can be broadly grouped into cardiac, which may be caused by structural heart disease or cardiac arrhythmias, and non-cardiac (Fitzpatrick and Cooper, 2006; Petkar et al, 2005).

Non-cardiac causes involve a range of systems:

  • Non-cardiac syncope, for example:

- Vasovagal syncope - the common faint (a reflex cause);

- Orthostatic hypotention (a postural cause);

- Cough syncope (a situational reflex cause);

  • Neurological conditions such as epilepsy;
  • Psychological factors such as anxiety;
  • Unexplained causes of T-LoC.

As the possible causes of T-LoC span a number of specialisms, diagnosis presents a particular challenge for healthcare professionals. A standard patient pathway should therefore be followed to ensure that diagnosis is quick, efficient and accurate, and that distress to patients and their families is minimised.

Distinguishing between syncope and epilepsy

Syncope is far more common than epilepsy, which occurs in just 0.5-1% of the general population (Department of Health, 2000) but is frequently misdiagnosed as epilepsy (Zaidi et al, 2000). This is because during a severe syncope ‘attack’, there may be a sudden collapse, twitching and jerking and even incontinence. These features are often associated with an epileptic seizure (Fitzpatrick, 2008).

Depending on the underlying causes of syncope, misdiagnosis or delayed diagnosis can be fatal and may cause immense distress and disruption to patients’ and carers’ lives. This is in addition to the distress caused by the condition itself. Misdiagnosis is also costly, placing an unnecessary burden on the NHS (Stokes et al, 2004).

Nurses working in A&E, primary care and specialist cardiology and epilepsy units can help in the diagnostic process through improved recognition of and distinction between the two conditions.


Syncope, or ‘anoxic seizure’, can be defined as ‘a sudden and brief loss of consciousness associated with a loss of postural tone, from which recovery is spontaneous’, and is caused by a sudden transient loss of blood flow to the brain (Kapoor, 2000).

This is usually due to a drop in blood pressure and/or a change in heart rhythm, causing a drop in the cardiac output and, ultimately, the amount of oxygenated blood reaching the brain (Brignole et al, 2004; Shaffer et al, 2001).

When blood pressure falls, several warning symptoms usually precede the loss of consciousness, such as light-headedness/dizziness, nausea, feeling hot and sweaty, fading vision and buzzing in the ears. However, if the heart stops pumping completely for a couple of seconds (bradycardia), blood flow stops more abruptly and there is often little, if any, warning before loss of consciousness (Syncope Trust And Reflex anoxic Seizures, 2007a). On occasion, jerking limb movements can develop. There may be urinary incontinence (Fitzpatrick, 2008) and, rarely, biting of the inside of the mouth or side of tongue.

Vasovagal syncope (also known as the ‘common faint’) is a reflex mechanism activated in response to a trigger such as the sight of blood or standing still for a long period (Brignole et al, 2004). It does not pose any long-term health risks itself, but could lead to high-risk situations, for example fainting while driving (Shaffer, 2001).

A more serious type of syncope can occur in children, although it is rare - reflex anoxic seizures or reflex asystolic syncope (RAS), also referred to as infantile vasovagal syncope (Brignole et al, 2004) - which is triggered by unexpected stimuli such as pain or fright. During an attack, the heart and breathing stop, the eyes roll into the head, skin may turn pale/grey, sometimes blue under the eyes and around the mouth. The body will stiffen and the arms and legs may jerk. After an attack, which will typically last for about 30 seconds, patients may remain unconscious for over an hour. On recovery they can be emotional and sleep for several hours (STARS, 2007b).

Other underlying causes of syncope can be more serious, such as the presence of structural heart disease or certain types of serious arrhythmia which can lead to sudden cardiac death (Kapoor, 2000). Examples of these are ventricular tachycardia or complete atrioventricular block (Fig 1), which is also known as complete heart block (Kapoor, 2000). These conditions need immediate treatment, so timely diagnosis is crucial. For different types of syncope and their prevalence, see Box 1.

Box1. Types and prevalence of syncope

Reflex, or ‘neurally mediated’ syncope, for example vasovagal syncope (66%)- a benign condition caused by an inbuilt reflex in response to external triggers

Cardiac cause (16%)- arrhythmia, tachycardia or bradycardia, or obstructive cardiac disorders such as aortic stenosis

Orthostatic hypotension (10%)- can be due to medication or diseases of the autonomic nervous system, such as Parkinson’s disease and diabetes mellitus

Other, rare presentations (6%)In this study, syncope remained unexplained in 2% of patients followed

Source: Brignole et al (2006)


Epilepsy seizures occur as the result of a sudden burst of excess electrical activity in the brain. Their frequency varies from multiple seizures a day to one every few years and they can affect people of all ages.

There are many different types of seizures depending on which part of the brain is affected, including brief ‘absent moments’ (a temporary loss of awareness or change in behaviour and emotions), partial or total loss of consciousness and convulsions. Body stiffness, tongue biting, loss of urinary and/or faecal continence, prolonged confusion and slow recovery after the event may also occur (Epilepsy Action, 2008).

Although not always evident, there are many triggers for epilepsy seizures, including: an underlying brain condition; lack of oxygen; low blood sugar; certain drugs; poisons; excess alcohol; and flickering lights (Epilepsy Action, 2008).

T-LoC is most likely to occur during a ‘generalised seizure’, where the abnormal electrical activity affects all or most of the brain (Epilepsy Action, 2008).

Impact of misdiagnosis

The similarity between a syncope ‘attack’ and epilepsy ‘seizure’ provides a diagnostic challenge even for specialists if trying to distinguish a case of syncope from one of epilepsy using visual cues alone.

UKresearch shows that approximately 150,000 people - around 30% of adults and 39% of children - diagnosed with epilepsy do not actually have the condition (Uldall et al, 2006). Many of these people will be unnecessarily treated with anticonvulsant medication, sometimes for decades. This is associated with side-effects that can have a negative impact on quality of life, for example affecting ability to work (Fitzpatrick, 2008; Zaidi et al, 2000).

Needless - and often expensive - diagnostic tests such as brain MRI or CT scanning can be stressful for patients and waste NHS resources.

Misdiagnosis also carries an economic cost. The All-Party Parliamentary Group on Epilepsy (2007) reported that the annual cost of epilepsy misdiagnosis in England is estimated to be around£189m a year. This takes into account unnecessary treatment costs, the economic costs of lost work and payment of disability living allowance, which itself totals£55m a year.

There are approximately 100,000 sudden cardiac deaths every year in the UK. The majority of those occurring in people under 30 years of age are due to inherited cardiomyopathies or arrhythmias (DH, 2005). The National Service Framework for Coronary Heart Disease recommends that measures are taken to improve the screening of patients who may be at risk of suffering from an arrhythmia, to ensure potential problems are detected and measures can be taken to reduce their risk (DH, 2005).

The need for specialist services

When there is doubt about the cause of an unexplained blackout, one solution is referral to specialist T-LoC clinics, which provide rapid access to the full range of neurological and cardiological diagnostic procedures. These are sometimes referred to as rapid access T-LoC clinics, or rapid assessment and treatment centres, and are run by multidisciplinary teams, led jointly by a cardiologist and a neurologist. This kind of service is the optimal setting in which to make the correct assessment and ensure appropriate specialist management for individual patients (Fitzpatrick, 2008).

Nurses can play an important role in referral to T-LoC clinics:

  • A&E nurses can help to ensure that patients admitted due to an unexplained T-LoC or fall are referred on to a T-LoC clinic;
  • Specialist nurses working in a T-LoC clinic can help carry out patient assessments, using the clinic’s assessment questionnaire, and discuss cases with the cardiologist and neurologist.

The NSF on coronary heart disease (DH, 2005) encouraged the creation of rapid access blackout/T-LoC clinics but, when it was published in 2005, no additional funding was made available. The framework refers to the ‘development of rapid access multidisciplinary arrhythmia and/or T-LoC clinics’ as part of its recommendation for service improvements.

As well as providing an invaluable single-entry clinical evaluation and shifting the judgement to a specialist multidisciplinary team, such clinics provide the potential to increase the number of specialist T-LoC nurses, ultimately improving patient services.

The cost to the NHS of establishing a T-LoC clinic service is relatively low, as many team members will be engaged in parallel activities. It offers a cost-effective means of delivering targeted diagnostic and therapeutic interventions. Tilt testing (a method of simulating/duplicating non-cardiac syncope) can cost up to the equivalent of£3,000 per diagnosis (Krahn et al, 2003), and implantable loop recorders (ILRs) (devices that can record ongoing ECG heart rhythm data) about£2,000, including both implantation and follow-up (Fitzpatrick and Cooper, 2006).

Speedy and accurate diagnosis prevents inappropriate NHS expenditure on ambulance journeys, A&E attendances and inpatient care, including unnecessary brain scanning and electroencephalograms. In most cases, these would cost far more than a dedicated T-LoC clinic (Brignole et al, 2004). Thus, once established, there is no doubt that such clinics would result in substantial cost savings for the NHS.

Ideally, a T-LoC clinic should exist in every district general hospital and tertiary centre. It is important that these clinics should be referred to as T-LoC or blackout clinics, as opposed to syncope clinics, to ensure that patients are not assumed to have syncope before a full assessment is carried out.

Part 2 of this unit explores the assessment and treatment of transient loss of consciousness.



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