Definition

• Transient self-limiting loss of consciousness
• Usually of rapid onset with spontaneous, complete and prompt recovery
• Underlying pathology is global hypoperfusion
• May be preceded by a feeling of faintness, light-headedness or muscular weakness (presyncope)
• evaluate presyncope in the same way as true syncope

Aim of assessment

• Majority of patients will have made a full recovery at point of assessment
• Low risk of serious adverse outcomes
• Aim to identify the small proportion with a significant underlying cause at risk of serious outcome

Principal causes

Reflex (neurally mediated) syncope

• Vasovagal (simple faint)
• suggested by the 3 P's (provocation, prodromal and positional elements)
• Situational
• micturition, cough, defecation, pain, swallowing
• Carotid sinus syndrome

Syncope from orthostatic hypotension

• After 3 min standing, a drop of >20 mmHg in systolic BP or 10 mmHg in diastolic BP or systolic BP to 90 mmHg
• autonomic failure
• drug-induced
• volume depletion (e.g. haemorrhage, diarrhoea, vomiting)

Cardiac syncope

• Arrhythmias
• bradycardia, tachycardia, implanted device failure
• Structural cardiac or cardiopulmonary disease
• e.g. valvular heart disease, LV systolic dysfunction, LV outflow obstruction, cardiac tamponade, pulmonary embolism
• Syncope during (rather than after) exercise

Differential diagnosis

Disorders with impairment or loss of consciousness

• Epilepsy
• Metabolic
• hypoglycaemia, hypoxia, hyperventilation with hypocarbia
• Intoxication
• TIAs of vertebrobasilar origin. See Transient ischaemic attack guideline

Disorders resembling syncope without loss of consciousness

• Falls. See Management of falls in A&E and wards guideline
• Cataplexy
• Functional: pseudosyncope, somatisation disorders
• TIAs of carotid origin. See Transient ischaemic attack guideline

History

Circumstances

• Before episode
• position, activity, predisposing factors or precipitating events
• Symptoms at onset of episode
• nausea, aura, visual, feeling warm/hot, cardiac symptoms
• Details of episode (eye-witness account, collateral history from paramedics)
• skin colour, duration of loss of consciousness, breathing pattern, movements, tongue biting, etc
• End of episode
• confusion, muscle aches, skin colour, injury, incontinence
• Brief non-specific symptoms/signs are common in syncope
• e.g. nausea, diaphoresis and brief myoclonic jerking
• Syncope may present as true seizure
• owing to cerebral hypoperfusion

Risk factors

• Previous presyncopal or syncopal episodes
• Previous cardiac and medical history
• Family history
• sudden cardiac death, epilepsy
• Medication
• Occupation and driving status

Physical examination

• Clinical assessment to identify serious underlying conditions
• e.g. abdominal aortic aneurysm, gastrointestinal bleed
• Vital signs at rest
• Evidence of orthostatic hypotension
• lying and standing BP
• Evidence of injury

Screening investigations

• 12-lead ECG
• If patient has an implanted cardiac monitor in situ, request interrogation of the device before discharge
• Blood tests useful only if clinically indicated
• e.g. haemoglobin for suspected haemorrhage
• Blood glucose
• Pregnancy test in women of childbearing age
• consider ectopic pregnancy

Red flag signs or symptoms

• Indicate patient may be at high risk of a serious adverse event
• request an urgent specialist assessment within 24 hr

Signs or symptoms

• ECG abnormality e.g.
  • evidence of ischaemia (pathological Qs, ST or T wave abnormal)
  • conduction defects (LBBB, RBBB, WPW, Brugada, any heart block, sinus pause >3 sec)
  • prolonged QT interval (abnormal: males >450 milliseconds, females >470 milliseconds)
  • marked bradycardia if not on beta-blockers
• Heart failure (history or physical signs)
• Transient loss of consciousness during exertion
• Family history
  • sudden cardiac death in people aged <40 yr
  • an inherited cardiac condition
• New or unexplained breathlessness or persistently abnormal vital signs
  • e.g. hypotension, hypoxia
• Heart murmur

Cardiovascular medication

• Adjust
• especially in elderly patients experiencing giddy spells with postural change and occasional syncope
• If, despite stopping antihypertensive medication, severe and symptomatic postural hypotension continues, consider midodrine 2.5 mg 3 times/day (typically on drug chart morning, lunch, teatime) - last dose should not be given at night to prevent supine hypertension. If no improvement titrate up to maximum dose of 10 mg 3 times/day 
• only start following discussion with a senior clinician
• Ensure patient and GP receive written instructions of any adjustments

Advise patient

• Avoid precipitating situations
• Maintain hydration
• Avoid becoming overheated
• If warning symptoms occur, take avoiding action
• Advise of the implications of their episode for health and safety at work
• any actions they must take to ensure safety
• Provide patient with advice on driving restrictions as per DVLA guidelines

Simple faint (vasovagal episode)

• Definite Provocational factors with associated Prodromal symptoms
• unlikely to occur whilst sitting or lying (Position)
• benign in nature
• If social circumstances favourable, discharge

Unexplained syncope: Low risk of recurrence

• No relevant abnormality on CVS and neurological examination and normal ECG
• If social circumstances favourable, discharge

Unexplained syncope: High risk of recurrence

High risk clinical features

• Abnormal ECG
• Clinical evidence of structural heart disease
• Sudden syncope occurring whilst driving, sitting, lying, on exertion or resulting in injury
• >1 episode in previous 6 months
• Family history of sudden cardiac death in people aged <40 yr
• Inherited cardiac condition

Admit

• If patient meets frail elderly criteria, request elderly care bed
• If cardiac cause suspected, discuss with cardiologist

Unwitnessed and/or altered awareness with seizure markers

• Strong clinical suspicion of epilepsy but no definite evidence. See First seizure guideline
• refer to first seizure clinic
• if social circumstances favourable, discharge

Referral to falls clinic

• If events frequent and/or patient sustained injuries, consider referral to falls clinic giving:
• relevant medical history
• reason for referral and information about recent falls and falls-related injuries
• details of known contributing factors