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CDHB

Syncope

Definition - a transient loss of consciousness. See also Altered Level of Consciousness.

Overview

After initial stabilization as needed, the aim is to diagnose the cause. In about 50% of patients the cause is obvious (e.g., GI bleed, epilepsy, hypoglycaemia, or classic vasovagal syncope). However in approximately 50% of people we will not ascertain the cause early on. In this undifferentiated group we aim to divide them into a "High Risk" group with respect to cardiac syncope, which should be referred, and a "Low Risk" group which can usually be discharged.

Indicators that may point to high risk syncope:

• Cardiac condition (ischaemic heart disease, conduction issues including permanent pacemaker in situ, aortic stenosis).
• Cardiac symptoms (e.g., palpitations or chest pain).
• Multiple episodes of syncope, or syncope in the horizontal position.
• Syncope on exertion.
• No vasovagal type prodrome (sudden onset).
• Drug overdose or toxicity.
• Advancing age.
• ECG abnormalities.

Initial assessment and resuscitation

• Airway
• Breathing
• Circulation

Consider telemetry if you are concerned that an arrhythmia is a likely cause of syncope. Refer to Telemetry Guidelines.

Complete assessment

History

The most important part of the assessment is a detailed history, which often requires talking to a witness. The ambulance report is extremely helpful here. Include a medication history, particularly hypotensive drugs, e.g., alpha-blockers, ACE inhibitors, diuretics.

Examination

• The examination should include careful palpation of pulse rate, rhythm, volume and character. The JVP should be measured in order to assess volume status.
• BP lying and standing with the heart rate response if there is a fall in blood pressure.
• Listen for murmurs, particularly the ejection murmur of aortic stenosis and hypertrophic obstructive cardiomyopathy.
• Assess for other possible causes of syncope, e.g., GI bleed, pulmonary embolus, sepsis etc.

Investigations

• 12 lead ECG - the most important test in undifferentiated syncope. Look for acute ischaemia, arrhythmias, and conduction abnormalities (e.g., heart block, bundle branch block, long QT, hypertrophic cardiomyopathy, Brugada syndrome, etc).
• Random blood sugar, Na, K, creatinine, CBC + diff when indicated.

Note: Troponins are not routinely required unless clinically indicated.

Possible causes

Possible causes, in order of prevalence:

• Vasovagal syncope (90%)

  Usually occurs when the torso is upright, has a prodrome, and may be triggered by needlestick phobia, standing in warm crowded rooms, or postural hypotension (particularly in the elderly). The commonest cause of postural hypotension in the elderly is drugs.

  Remember that vasovagal syncope can occur in patients who are in a low output state because of a serious underlying condition, e.g., pulmonary embolus, septic shock, GI bleeding, ruptured ectopic pregnancy.

• Cardiac syncope (5-10%)

  Classically occurs during exertion and may be preceded by angina or palpitations. It is usually rapid in onset and offset. It should be considered in anyone with a symptomatic cardiac condition. It carries a poor prognosis, so if suspected, the patient should be admitted and monitored.

• Epilepsy (0-5%)

  These patients tend to fall and injure themselves (e.g., tongue bite). There may be a preceding aura. There is often post-ictal confusion and drowsiness for one to two hours. More common during sleep.

• Miscellaneous causes:
  • Hypoglycaemia
  • Alcohol
  • Psychogenic
  • TIA/stroke is an exceedingly rare cause of syncope and can be clinically excluded if there is no focal neurology. Syncope may occur at the onset of sub-arachnoid haemorrhage.

Topic Code: 1269