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Presyncope / Syncope



  • Presyncope is a feeling of lightheadedness or of being about to ‘faint'. Syncope is the transient loss of consciousness, or the act of ‘fainting'.
  • Often patients present with ‘dizziness', which may refer to lightheadedness, vertigo, motor instability or anxiety. It is important to gain further history and differentiate between these symptoms.


    • Causes of Presyncope / Syncope

    • Neurally Mediated

    • Vasovagal syncope
    • Situational - coughing, micturition, defaecation, playing brass instruments, valsalva
    • Carotid sinus syndrome - hypersensitivity of the carotid sinus
    • Cardiac

    • Arrhythmia - sick sinus, AV block, SVT, AF, VT
    • Structural - aortic stenosis, acute coronary syndrome, obstructive cardiomyopathy
    • Orthostatic

    • Volume loss - dehydration, haemorrhage
    • Primary autonomic failure - Parkinson’s, multisystem atrophy, MS
    • Secondary autonomic failure - diabetic neuropathy, amyloidosis, HIV neuropathy, CIPD
    • Drugs - antihypertensives, vasodilators, diuretics, antidepressants
    • Cerebrovascular

    • Stroke / TIA
    • Vascular steal syndrome
    • Other

    • Pulmonary embolism

Differential Diagnosis

    • Differential Diagnosis for Dizziness

    • Spinning Sensation - that the patient or the room is spinningVertigo, i.e. vestibular pathology
    • Lightheadedness - a feeling of nearly faintingPresyncope
    • Dysequilibrium - a feeling of poor balanceGait disorder
    • Overwhelmed sensation - a disconnection from the worldAnxiety
    • Differential Diagnosis for Loss of Consciousness

    • Intracranial

    • Haemorrhage - intracerebral, subarachnoid, subdural, extradural
    • Infarction
    • Infection - meningitis, encephalitis, abscess
    • Tumour - mass effect, cerebral oedema
    • Post ictal state
    • Head trauma - vascular, hypoxia, cerebral oedema, parenchymal injury
    • Psychiatric - conversion, depression, catatonia
    • Extracranial

    • Cardiovascular - shock, hypertension
    • Infection - septicaemia
    • Metabolic - hypo/hyperosmolar states, hypo/hyperglycaemia, hypothyroidism, hypopituitarism, electrolyte abnormality, hypoxia, hepatic failure, renal failure
    • Endocrine - adrenal crisis, myxoedema coma
    • Drugs / toxins - sedatives, analgesics, alcohol
    • Physical injury - hyper / hypothermia, electrocution

History of Presenting Complaint

    • Trigger

      Whether there was anything that may have precipitated the presyncope or syncope.
    • Standing after lying / sittingSuggestive of vasovagal syncope or orthostatic hypotension
    • NOT triggered by postural changeSuggestive of arrhythmia
    • Pain or emotional stressVasovagal syncope
    • Venesection or seeing bloodVasovagal syncope
    • EatingSituational (postprandial) syncope
    • Micturition or defaecationSituational (micturition / defaecation) syncope
    • Paroxysm of coughSituational syncope
    • Weightlifting or playing a brass instrumentSituational (weightlifter’s / trumpet player’s) syncope
    • Head rotation or wearing a tight collarSuggestive of carotid sinus syndrome
    • ShavingSuggestive of carotid sinus syndrome
    • ExerciseSuggestive of arrhythmia or cardiac structural disease
    • Arm exercisesSuggestive of vascular steal syndrome
    • Before the Episode

      Whether the patient had any symptoms just prior to the episode of syncope.
    • LightheadednessSuggestive of syncope, rather than seizure
    • Nausea, flushing and diaphoresisSuggestive of vasovagal syncope
    • Chest pain +/- diaphoresisSuggestive of acute coronary syndrome or pulmonary embolism
    • Arm / leg weakness or facial droopSuggestive of stroke / TIA
    • Shortness of breathMay represent heart failure in the setting of aortic stenosis
    • PalpitationsSuggestive of arrhythmia
    • Visual changes or altered sense of smellSuggestive of preictal state
    • During the Episode

    • Loss of consciousness for a few secondsMore suggestive of syncope than seizure
    • Short episode of myoclonic movementMore suggestive of vasovagal than seizure
    • Tonic-clonic movementsSuggestive of seizure rather than syncope
    • Tongue biting or urinary incontinenceSuggestive of seizure rather than syncope
    • After the Episode

    • Nausea and vomitingSuggestive of vasovagal syncope
    • Short period of disorientationMay occur post vasovagal
    • ConfusionSuggestive of post-ictal period
    • Arm / leg weakness or facial droopSuggestive of stroke / TIA
    • Timing

    • The frequency and duration of these episodes.
    • Associated Symptoms

      Whether the patient has been unwell recently.
    • Vomiting or diarrhoeaSuggestive of orthostatic hypotension due to volume loss
    • PR bleeding, malaena or haematemesisSuggestive of orthostatic hypotension due to volume loss
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