Chester County Medicine Winter 2021 - 10

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Syncope: Not Just for the Faint of Heart
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Introduction

What Causes Syncope?

Syncope, also known as fainting, is transient loss of
consciousness and motor function with sudden onset and
spontaneous recovery of function and consciousness. Syncopal
episodes account for between 3% and 5% of emergency
department visits with 40% of syncope patients requiring
hospitalization. Decreases in blood pressure or pulse rate are
the most common causes of syncope because in both cases, not
enough oxygen is transported by the blood to the brain, causing it
to essentially " shut down " for a brief period. Episodes of syncope
can last from just seconds to several minutes of being unconscious.

Although the syncopal episode itself is the result of insufficient
blood flow to the brain, there are several subtypes of syncope
that differ by what causes this. The four major subtypes of
syncope are reflex, postural, cardiac arrhythmic, and structural
cardiopulmonary. Additionally, almost 10% of syncopal episodes
have an unknown origin.
Reflex syncope is the first subtype of syncope where the
nervous system improperly modulates and decreases blood
pressure, resulting in loss of consciousness. Reflex syncope
accounts for roughly 60% of syncopal episodes in adults. Reflex
syncope encompasses vasovagal syncope and carotid sinus
syndrome.
In the case of vasovagal syncope, stimuli causing emotional
distress or specific situations cause patients to lose consciousness
temporarily. In either case, the vasovagal reaction, where heart
rate is reduced while blood vessels in the body dilate, leads to
insufficient blood flow to the brain. The cause of carotid sinus
syndrome remains somewhat of a mystery to doctors to this day.
It is clinically identified by hypersensitivity to, or fainting from
carotid sinus massage.
Postural syncope, aalso called orthostatic hypotension, is
another subtype of syncope caused by a decrease in blood pressure
after standing up from a seated position or from laying down
position. Decreases of 20 mmHg systolic pressure and 10 mmHg
diastolic pressure are sufficient to reduce nutrient supply to the
brain enough to cause syncopal episodes.

Figure 1: A woman suffering from syncope.

Symptomology
* Common symptoms
	 o Blacking out
	 o Feeling lightheaded
	 o Dizziness
	 o Feeling drowsy or " out of it "
	 after sitting or laying down
	 o Changes in vision
*	Less common symptoms
	 o Heart palpitations
	 o Nausea
	 o Fluttering in chest

10 CHESTER COUNT Y Medicine | WINTER 2021

Figure 2 - Orthostatic hypotension causing presyncope.
Immediate orthostatic hypotension can result in loss of
consciousness or near loss of consciousness occurring within 10 to
20 seconds of standing up. Sitting back down or bracing oneself
against furniture can typically negate total loss of consciousness.
Immediate orthostatic hypotension is considered more benign
than delayed orthostatic hypotension because of the patient's
ability to brace themselves before falling.
Chester County Medicine Winter 2021

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