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Syncope, Synkope, Sɪŋkəpi: Swooning Explained

By: , Posted on: May 24, 2016

Stage actress Sarah Bernhardt, (born Henriette Rosine Bernard, 1844 - 1923), arguably the greatest tragedienne of her day, in a scene from an unnamed theatre production. Original Publication: People Disc - HW0437 (Photo by Hulton Archive/Getty Images)
Stage actress Sarah Bernhardt, (born Henriette Rosine Bernard, 1844 – 1923), arguably the greatest tragedienne of her day, in a scene from an unnamed theatre production. Original Publication: People Disc – HW0437 (Photo by Hulton Archive/Getty Images)

Syncope, also referred to as ‘fainting’, ‘passing-out’ or ‘swooning’, occurs as a result of a transient loss of consciousness and muscle strength. It affects around 1 in 3 people. Typically it is quick to occur, has a relatively short duration and people tend to recovery quickly. Perhaps the best known form of fainting happens at the sight of blood with more surprising examples including forms where people pass-out when coughing and straining for bowel movement. Yet it still remains unexplained in 10% to 40% of cases. The current article discusses some of the most common causes of syncope.

During the Victorian times it was fashionable for well-bred ladies to “swoon” or “fall-out” at a particular dramatic event.  Well-to-do ladies had a special room called “fainting room” where they could recover from a fainting spell or hysteria. Notable cure for fainting spells was smelling salts or ammonium carbonate.

It is estimated that around 30% of people have fainted at one time in their life and that the cause for this remains unexplained for between 1 and 4 out of every 10 sufferers [1]. Fainting is a temporary loss of consciousness followed by full return to wakefulness. The medical term for fainting is “Syncope” derived from Greek word “synkope” meaning “contraction” or “cutting off”. Most fainting spells are nothing to worry about, but if you experience recurrent spells you should consult a doctor.

The common causes

A recent article published in the journal of Circulation [1] describes the sensation of syncope as:

“…a form of transient loss of consciousness caused by insufficient blood flow to the brain characterized by a rapid onset, short duration, and spontaneous and complete recovery.”

The most common causes for syncope are orthostatic hypotension, of reflex origin or of cardiovascular origin. At this juncture it is also important to also ask if syncope is unique to humans. Dr Bob Sheldon Canadian Dr Sheldon says this is a condition that uniquely affects humans, but does jokingly point to some interesting animal models of fainting such as the Tennessee fainting goat which humorously fall-over and seem to replicate at least the act of falling over [2].

Orthostatic hypotension and syncope

This is commonly referred to as low blood pressure and can occur during changes in posture such as going from sitting down to standing upright, where blood pressure momentarily drops and the heart works hard to counter the change in posture induced drop of pressure. Anyone that has relaxed in a warm bath for a prolonged period of time will be well aware of the sensations experienced when quickly changing from a lying to standing position. Symptoms can include sweating, nausea, light-headedness and visual blurring [1].

These symptoms would not be too dissimilar to those experienced when going into a hot tub or sauna. At the World Sauna Championships competitors are exposed to an ‘extreme sauna’ experience with the temperature starting at 110°C (230°F) and water being thrown onto the heater every thirty seconds [2]. The last person left sitting is the winner. However, this can be potentially fatal, and was for one contestant in 2013, as the body adapts to the heat. This involves increased blood flow to the skin to promote cooling of the body. This is accompanied by a drop in blood pressure and a rise in heart rate, which works well until the body cannot meet the demand being placed on it. Such as losing too many fluids, or the heart not being able to maintain its work rate or sweat stops evaporating from the skin and the body is no longer being cooled.

Orthostatic hypotension (and syncope) can also occur after commencing new medicines, drinking alcohol and from heavy blood loss.

Reflex and syncope

Syncope caused by a reflex refers to the body’s natural response to a stimulus. A common example cited here is prolonged standing and this is commonly seen in the military where soldiers stand on parade for several hours. Indeed, an article published in the Express by Tom Coghlan [4] highlighted how soldiers were learning to survive standing on their feet during the wedding of Prince William and Catherine Middleton.

fainting guard

The ceremony lasted four hours with soldiers ‘stood to attention’ whilst fully dressed in a bearskin, a tunic and a thick pair of barathea wool trousers. The standard bearskin of the British Foot Guards measures 18 inches in height weighs one-and-a-half pounds, is well insulated with the fur from Canadian black bears and is fastened in position with a leather band. The uniform is also not exactly ‘lightweight’ as the tunic has 11 layers of cloth and is designed to hide any sweat patches. And, the trousers are thick wool. In relation to preventing a faint, the soldiers were advised:

“ offset the risk of fainting while on duty by ensuring that the leather band on their bearskin is not too tight so that their heads can expand in the heat and by drinking up to five litres of water beforehand.”

Cardiovascular origins and syncope

The last cause relates to abnormalities arising from the heart. Stephen Kidd [1] mentions that this type of syncope is usually the result of abnormalities leading to unusually fast or slow heart rates, and even sudden death. Any one that is a fan of the Premiership will hopefully have heard that Leicester City, achieving odds of 5000 to 1 to win the title at the start of the season, won the title this year.  Similarly, fans will also be very aware of the footballer Fabrice Muamba who collapsed on the pitch in 2012 during the Football Association cup tie between Bolton Wanderers and Tottenham Hotspurs [5]. This was linked to hypertrophic obstructive cardiomyopathy (also known as ‘HOCM’). The American Heart Association {6} defines HOCUM as:

Hypertrophic cardiomyopathy occurs if heart muscle cells enlarge and cause the walls of the ventricles (usually the left ventricle) to thicken. The ventricle size often remains normal, but the thickening may block blood flow out of the ventricle. If this happens, the condition is called obstructive hypertrophic cardiomyopathy.”

The significance of syncope and sudden death in relation to HOCUM has previously been investigated in 1,511 patients with this condition [7]. Results showed that patients with unexplained syncope had a higher risk (5-fold higher) of sudden death than patients without syncope. And, the risk was higher if the syncope event occurred within 6 months of the initial HOCUM evaluation.

Heart disease as well as overactive thyroid and certain medications can also be classified as cardiovascular in origin and considered causes in this categorization of syncope.

About the Authors

ela thakoreEla Thakore worked at the University of Calgary for 30 years developing models of syncope and heart rate variability.

chris wrightChristopher Wright is the founder of Red Pharm communications. He graduated from the University of Leeds with a PhD in applied cardiovascular physiology. His thesis focused on models of syncope and the control of blood pressure and heart rate.

Please contact the author for reference materials cited in this article –

[1] Stephen K. Kidd, MD; Christopher Doughty, MD; Samuel Goldhaber, MD
Syncope (Fainting). Circulation. 2016; 133:e600-e602. Source: Accessed: May 13 2016.
[2] How saunas can become lethal. In the Discovery newsletter published on February 11 2013. Source: Accessed: May 13 2016.
[3] Fainting research. An interview with Dr. Bob Sheldon, professor of cardiac sciences at the University of Calgary, discusses an ongoing study into what causes fainting that took place on June 3 2015. Source: Accessed: May 13 2016.
[4] Tom Coughlan. Royal guards who are taught how to faint. Published in the Express on April 22 2011. Source: Accessed: May 13 2016.
[5] BBC Sports webpage. Source: Accessed: May 13 2016.
[6] American Heart Association webpage. Definition of Hypertrophic Cardiomyopathy. Source: Accessed: May 13 2016.
[7] Paolo Spirito, MD. Syncope and Risk of Sudden Death in Hypertrophic Cardiomyopathy. Circulation 2009;   119:  1703-1710. Source:
Accessed: May 13 2016.

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