Syncope toolkit

Syncope is very common and will affect 42% of people during their lifetime

Orthostatic hypotension

Orthostatic hypotension is the mechanism of syncope in around 10% of patients.

In this section:


Classical OH: a progressive and sustained fall in systolic blood pressure from baseline value greater than or equal to 20 mmHg or diastolic blood pressure greater than or equal to 10 mmHg, or a decrease in systolic blood pressure to less than 90 mmHg which usually occurs within three minutes of standing.

Initial postural hypotension (head rush): blood pressure decrease on standing of more than 40 mmHg systolic blood pressure usually with more than 20 mmHg drop in diastolic blood pressure within 15 seconds of standing. This is a common cause of syncope in young people.

Delayed postural hypotension: blood pressure fall occurs after three minutes (and may occur more than 10 minutes after standing). This is common in the elderly.

Note that the definition of orthostatic hypotension does not state whether the fall in blood pressure should or should not be accompanied by symptoms.

Some patients with chronic orthostatic hypotension can remain conscious despite extraordinarily low blood pressure due to effective cerebral autoregulation.

Orthostatic hypotension can be a chronic, debilitating illness that is associated with reduced quality of life, risk of falls, cognitive impairment and increased mortality. It is common and affects up to 20% of older people living at home and almost one in four older people in long-term care.

Symptoms of orthostatic hypotension

Symptoms include:

  • Light-headedness
  • Difficulty thinking
  • Orthostatic headache
  • Fatigue, weakness
  • Nausea
  • Visual and hearing disturbances (such as black or white dots, greying out, temporary loss of vision, ringing or rushing sounds)
  • Posterior neck discomfort (coat hanger pain)
  • Syncope
  • Recurrent unexplained falls.

Exacerbating factors:

  • Standing
  • More severe in the morning
  • Worse immediately after exercise
  • High environmental temperature
  • After meals (post-prandial hypotension)
  • After prolonged bedrest (deconditioning).

Relieving factors:

  • Lying down
  • Less severe or absent when sitting.

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Causes of orthostatic hypotension

Medication induced (most common cause)
  • Vasodilators
  • Diuretics
  • Antihypertensives
  • Beta blockers
  • Alpha-adrenoceptor blockers
  • Anti-Parkinson drugs, for example levodopa, ropinerole
  • Tricyclic and non-tricyclic antidepressants
  • Insulin (in diabetic patients with autonomic failure)
  • Narcotics
  • Drugs that induce autonomic neuropathy, for example amiodarone, chemotherapy.
Volume depletion
  • Haemorrhage (possibly gastro-intestinal)
  • Diarrhoea
  • Vomiting.
Primary autonomic failure
  • Pure autonomic failure
  • Multisystem atrophy
  • Parkinson’s Disease
  • Lewy Body Dementia.
Secondary autonomic failure
  • Diabetes
  • Amyloidosis
  • Spinal cord injury
  • Auto-immune autonomic neuropathy
  • Paraneoplastic autonomic neuropathy
  • Renal failure.
Other causes
  • Adrenal insufficiency
  • Cardiac impairment, such as myocardial infarction, aortic stenosis
  • Vasodilatation, for example fever, sepsis.

See Management of orthostatic hypotension

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Orthostatic hypotension case histories