A vasovagal episode or vasovagal response or vasovagal attack is a malaise mediated
by the vagus nerve.
When it leads to syncope or "fainting", it is called a vasovagal syncope, which is the
most common type of fainting.
Vasovagal syncope more commonly affects young adults.
There are different syncope syndromes which all fall under the umbrella of vasovagal syncope.
The common element among these conditions is the central mechanism leading to loss of
consciousness.
The differences among them are in the factors that trigger this mechanism.
Signs and symptoms Episodes of vasovagal response are typically
recurrent, and usually occur when the predisposed person is exposed to a specific trigger.
Prior to losing consciousness, the individual frequently experiences early signs or symptoms
such as lightheadedness, nausea, the feeling of being extremely hot or cold, ringing in
the ears, an uncomfortable feeling in the heart, fuzzy thoughts, confusion, a slight
inability to speak/form words, weakness and visual disturbances such as lights seeming
too bright, fuzzy or tunnel vision, black cloud-like spots in vision, and a feeling
of nervousness can occur as well.
The symptoms last for a few seconds before the loss of consciousness, which typically
happens when the person is sitting up or standing.
When sufferers pass out, they fall down and, when in this position, effective blood flow
to the brain is immediately restored, allowing the person to regain consciousness; if the
person does not fall into a fully flat, supine position, and the head remains elevated above
the trunk, a seizure may result from the blood's inability to return quickly to the brain.
Fainting occurs with the loss of oxygen to the brain.
The autonomic nervous system's physiologic state leading to loss of consciousness may
persist for several minutes, so: If sufferers try to sit or stand when they
wake up, they may pass out again The person may be nauseated, pale, and sweaty
for several minutes or hours Cause
Vasovagal syncope occurs in response to a trigger, with a corresponding malfunction
in the parts of the nervous system that regulate heart rate and blood pressure.
When heart rate slows, blood pressure drops, and the resulting lack of blood to the brain
causes fainting and confusion.
Typical triggers for vasovagal episodes include: Prolonged standing or upright sitting
Standing up very quickly Stress directly related to trauma
Stress P.O.T.S.
Multiple chronic episodes are experienced daily by many patients diagnosed with this
syndrome.
Episodes are most commonly manifested upon standing up.
Any painful or unpleasant stimuli, such as: Trauma
Watching or experiencing medical procedures) High pressure on or around the chest area
after heavy exercise
Severe menstrual cramps Sensitivity to pain
Arousal or stimulants, e.g. sex, tickling or adrenaline
Sudden onset of extreme emotions Lack of sleep
Dehydration Hunger
Being exposed to high temperatures In health care, such as nursing care, digital
rectal procedures Random onsets due to nerve malfunctions
Pressing upon certain places on the throat, sinuses, and eyes
Use of certain drugs that affect blood pressure, such as cocaine, alcohol, marijuana, inhalants
and opiates The sight of blood
Serotonin level / SSRI Swallowing
(Less commonly) Low blood sugar Time varying magnetic field
Pathophysiology Regardless of the trigger, the mechanism of
syncope is similar in the various vasovagal syncope syndromes.
In it, the nucleus tractus solitarii of the brainstem is activated directly or indirectly
by the triggering stimulus, resulting in simultaneous enhancement of parasympathetic nervous system
tone and withdrawal of sympathetic nervous system tone.
This results in a spectrum of hemodynamic responses:
On one end of the spectrum is the cardioinhibitory response, characterized by a drop in heart
rate and in contractility leading to a decrease in cardiac output that is significant enough
to result in a loss of consciousness.
It is thought that this response results primarily from enhancement in parasympathetic tone.
On the other end of the spectrum is the vasodepressor response, caused by a drop in blood pressure
without much change in heart rate.
This phenomenon occurs due to vasodilation, probably as a result of withdrawal of sympathetic
nervous system tone.
The majority of people with vasovagal syncope have a mixed response somewhere between these
two ends of the spectrum.
One account for these physiological responses is the Bezold-Jarisch reflex.
Diagnosis In addition to the mechanism described above,
a number of other medical conditions may cause syncope.
Making the correct diagnosis for loss of consciousness is one of the most difficult challenges that
a physician can face.
The core of the diagnosis of vasovagal syncope rests upon a clear description by the patient
of a typical pattern of triggers, symptoms, and time course.
It is also pertinent to differentiate lightheadedness, seizures, vertigo, and hypoglycemia as other
causes.
In patients with recurrent vasovagal syncope, diagnostic accuracy can often be improved
with one of the following diagnostic tests: A tilt table test
Implantation of an insertable loop recorder A Holter monitor or event monitor
An echocardiogram An electrophysiology study
Treatment Treatment for vasovagal syncope focuses on
avoidance of triggers, restoring blood flow to the brain during an impending episode,
and measures that interrupt or prevent the pathophysiologic mechanism described above.
The cornerstone of treatment is avoidance of triggers known to cause syncope in that
person.
However, a new development in psychological research has shown that patients show great
reductions in vasovagal syncope through exposure-based exercises with therapists if the trigger is
mental or emotional, e.g. sight of blood.
However, if the trigger is a specific drug, then avoidance is the only treatment.
Because vasovagal syncope causes a decrease in blood pressure, relaxing the entire body
as a mode of avoidance is not favorable.
A patient can move or cross his/her legs and tighten leg muscles to keep blood pressure
from dropping so drastically before an injection.
Before known triggering events, the patient may increase consumption of salt and fluids
to increase blood volume.
Sports drinks or drinks with electrolytes may be particularly helpful.
Discontinuation of medications known to lower blood pressure may be helpful, but stopping
antihypertensive drugs can also be dangerous in some people.
Taking antihypertensive drugs may worsen the syncope, as the hypertension may have been
the body's way to compensate for the low blood pressure.
Patients should be educated on how to respond to further episodes of syncope, especially
if they experience prodromal warning signs: they should lie down and raise their legs,
or at least lower their head to increase blood flow to the brain.
If the individual has lost consciousness, he or she should be laid down with his or
her head turned to the side.
Tight clothing should be loosened.
If the inciting factor is known, it should be removed if possible.
Wearing graded compression stockings may be helpful.
There are certain orthostatic training exercises which have been proven to improve symptoms
in people with recurrent vasovagal syncope.
A technique called "Applied Tension" which involves learning to tense the muscles in
the torso, arms, and legs is effective for vasovagal syncope.
Certain medications may also be helpful: Beta blockers were once the most common medication
given; however, they have been shown to be ineffective in a variety of studies and are
thus no longer prescribed.
In addition, they may cause the syncope by lowering the blood pressure and heart rate.
Other medications which may be effective include: CNS stimulants fludrocortisone, midodrine,
SSRIs such as paroxetine or sertraline, disopyramide, and, in health-care settings where a syncope
is anticipated, atropine epinephrine.
For people with the cardioinhibitory form of vasovagal syncope, implantation of a permanent
pacemaker may be beneficial or even curative.
Types of Long-Term Therapy for Vasovagal Syncope include:Preload agents
Vasoconstrictors Anticholinergic agents
Negative cardiac inotropes Central agents
Mechanical device
Prognosis Brief periods of unconsciousness do no harm
and are seldom symptoms of disease.
The main danger of vasovagal syncope is the risk of injury by falling while unconscious.
Medication therapy could possibly prevent future vasovagal responses; however, for some
individuals medication is ineffective and they will continue to have fainting episodes.
See also Roemheld Syndrome
References
External links Dysautonomia International
Dysautonomia Information Network Dysautonomia Youth Network of America, Inc.
Seattle Community Network Autism – Information regarding syncope
Mik's Hidden Hearts Alliance for Dysautonomia 12 More Pages-Live & Cope with Dysautonomia