Transient Loss of Consciousness - Patient History

Patient History

When a patient presents with an episode of transient loss of consciousness it is important to take a good history including a family history.

• The family history may highlight a familial history of sudden unexpected death, or a familial propensity to neurally mediated syncope.
• The patient history may indicate if the patient has underlying heart disease, which would predispose them to a cardiac cause of syncope.
  • It will also indicate if they have risk factors for neurally mediated or other hypotensive causes of syncope.
• Medications may be implicated as a cause or contributing factor to episodes of syncope.

Family History

When assessing for a family history of serious cardiac conditions ask specifically about:

Any family history of:

• Premature sudden death
• Include single vehicle accidents
• Drowning
• SIDS
• Death following a fall with injury
• Death during sleep/exertion

Any family history of:

• Cardiomyopathy
• Hypertrophic Cardiomyopathy
• Long QT
• Brugada syndrome
• Arrhythmogenic right ventricular dysplasia

Benign conditions are also often familial

Ask about family history of:

• Neurally mediated syncope
• Low blood pressure

Patient Past History

Ask about Cardiac Risk Factors

• Ischaemic heart disease
• Previous myocardial infarct
• Prior cardiac surgery
• Hypercholesterolaemia
• Hypertension
• Diabetes
• Smoking

Ask about Neurological Risk Factors

• Vascular risk factors as above
• History of cerebrovascular disease
• History of head injury
• Why did they injure their head – were they syncopal?
• History of brain surgery
• History of prior malignancies

Ask about Neurally Mediated/Hypotensive Episode Risk Factors

Previous episodes of syncope occuring in 'classical' neurally mediated circumstances:

• In church/banks/supermarkets/shopping centres
• Sight of blood
• Soldiers on parade/children in assembly or school concerts
• Prolonged standing on warm days

Conditions associated with abnormalities of the autonomic nervous system, which controls the normal response to the upright posture.

• Diabetes
• Hypertension
• Parkinson's disease
• Alcohol

Conditions that may encourage fluid restriction and therefore dehydration:

• Bladder dysfunction
• Incontinence issues

Conditions that worsen peripheral venous pooling:

• Varicose veins
• Obesity - mechanical compression

Other relevant information:

• Salt and fluid intake
• Exercise without adequate fluid replacment
• Unusual dietary practices
• High caffeine/ low non-caffeine fluid intake
• Alcohol intake - relationship to timing of episodes eg the day after heavy alcohol intake.

Medications

Medications can cause or exacerbate syncope by a number of mechanisms:

• Hypotension
  • Due to vasodilation or dehydration
• Bradycardia
• Proarrhythmia

Or multiple combinations of the above.

Ask specifically about the different classes below and time of initiation or taking in relation to the episode.

• Antihypertensives
  • Diuretics
  • Short-acting agents
• Nitrates
• Agents causing bradycardia/conduction block/ proarrhythmia
  • Non-dihydropyridine calcium antagonists
  • Beta blockers
  • Antiarrhythmic agents (can be proarrhythmic)
• QT prolonging agents
  • eg Antibiotics / antiarrhythmics /antidepressents
  • OTC meds - pseudoephedrine
• Anticholinergic agents
• Antidepressants
• Herbal preparations
  • diuretic properties
• Recreational drugs
• Agents used for treatment of impotence.

The time course in relation to symptoms is important:

• Patients experiencing syncope one week after introduction of a new antihypertensive are likely to have Orthostatic Hypotension.
• Elderly patients presenting with syncope after breakfast may be taking a number of antihypertensives and other vasodilators first thing in the morning – exacerbating postprandial hypotension.

History of the event

The history of the episodes, the circumstances in which they occurred and the time to recovery can be very helpful in indicating the likely cause.

The table below highlights the typical clinical features of various causes of transient loss of consciousness.

In particular:

• Diaphoresis, abdominal discomfort and nausea and vomiting are particularly sensitive for neurally mediated syncope. Post event lethergy is also quite specific to this cause.
• Cardiac syncope is generally associated with a very rapid recovery without post-event lethergy.
• Episodes of unresponsiveness without loss of postural tone are consistent with partial seizures
• Patients can have co-existant syncope and seizures
  • Ictal bradycardia - with asystole- is well documented during seizures, particularly of left temporal lobe origin.
• In general recovery is rapid after syncope, however a longer period of unresponsiveness/confusion post episode can occur in neurally mediated and other forms of hypotensive syncope particularly if:
  • The patient was kept upright during the episode
  • The patient is elderly with diminished reserve or comorbid crebrovascular disease.
  • Some younger patients with neurally mediated syncope - ? due to cerebral vasoconstriction +/- hyperventilation.