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About Syncope

CAUSES

Syncope can be classified into 4 categories:

Neurally-mediated syncope

One cause of neutrally medicated syncope is vasovagal syncope, whereby there is a sudden drop in blood pressure and heart rate, which causes a decreased blood flow to the brain. Situational syncope also falls under this category and happens during certain situations that affect the nervous system including:

  • Dehydration
  • Emotional stress
  • Fear and anxiety
  • Pain

This type of syncope is usually harmless however your doctor may recommend tests to rule out a more serious cause.

Orthostatic hypotension

Orthostatic hypotension is caused by quick drop in blood pressure caused when a patient goes from sitting or lying to standing. Autonomic nervous system failure or volume depletion can also cause this type of syncope. Some medications may also contribute. 

Cardiac syncope

Cardiac conditions causing syncope can include an abnormal heart rhythm (too fast or too slow), a blockage in the cardiac blood vessels or altered blood flow. This type of syncope usually requires further investigation to find a cause, and possibly treatment.

Neurological syncope

Neurologic syncope is caused by a neurological condition such as seizure, stroke or transient ischemic attack (TIA) and requires further investigation.

Brignole et al. Heart 2007: 93: 130-136

SYMPTOMS

The most common symptoms of syncope include:

  • Blacking out
  • Light-headedness or dizziness
  • Falling for no reason
  • Drowsiness
  • Fainting after eating or exercising
  • Changes in vision
  • Headaches

Red Flags for Cardiac Syncope

A patient should seek urgent referral for specialist assessment if they have any of the following:

  • ECG abnormality
  • Heart palpitations (feeling like your heart is racing or pounding)
  • Pain, tightness or discomfort in the chest
  • Syncope during exertion or lying down
  • Family history of sudden cardiac death
  • New or unexplained breathlessness
  • A heart murmur.

National Institute for Health and Care Excellence (NICE),Transient loss of consciousness ('blackouts') management in adults and young people, NICE clinical guideline 109, Issued: August 2010 last modified: September 2014

Historical characteristics associated with increased probability of cardiac causes of syncope1

  • Older age (> 60 yr)
  • Male sex
  • Presence of ischemic heart disease, structural heart disease, previous arrhythmias, or reduced ventricular function
  • Brief (palpitations) or no symptoms prior to loss of consciousness
  • Occurs with exertion
  • Occurs in supine position
  • Low number of events (1 or 2)
  • Abnormal cardiac examination
  • Family history of inheritable conditions or premature SCD (< 50 yr of age)
  • Presence of known congenital heart disease

References

1 Shen WK, et al. 2017 ACC/AHA/HRS Guideline for the Evaluation and Management of Patients With Syncope. J Am Coll Cardiol. 2017. DOI: 10.1016/j.jacc.2017.03.003.

DIAGNOSIS

A comprehensive medical history is taken and a complete physical examination. The following tests may be performed to help determine the cause of syncope:

Refer to HeartCare Partners Tests Information Sheets here

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