Vasovagal syncope is the most common cause of syncope, also known as fainting. There are a number of 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 which trigger this mechanism. Fainting (IPA: or ) is a sudden (and generally momentary) loss of consciousness, or blacking out due to the Central Ischaemic Response, because of a lack of sufficient blood and oxygen reaching the brain. ...

Triggers

Typical triggers for vasovagal syncope include:

• prolonged standing or upright sitting
• stress
• any painful or unpleasant stimuli, such as
  • giving blood
  • watching someone else give blood
  • watching someone experience pain
• prolonged exposure to heat
• sudden onset of extreme emotions
• hunger
• consumption of marijuana
• consumption of alcohol
• nausea or vomiting
• urination ('micturition syncope') or defecation
• swallowing ('deglutition syncope')
• sexual arousal
• abdominal straining or 'bearing down' (as in defecation)
• random onsets due to nerve malfunctions
• Pressing upon certain places on the throat, sinuses, and eyes.

People with trypanophobia ("injection phobia"), traumatophobia or blood phobia may suffer from vasovagal syncope from the sight, feeling, or even thought of a needle. In medical terms, stress is the disruption of homeostasis through physical or psychological stimuli. ... “Give blood” redirects here. ... This article or section does not cite any references or sources. ... Hunger is a feeling experienced when the glycogen level of the liver falls below a threshold, usually followed by a desire to eat. ... A dried flowered bud of the Cannabis sativa plant. ... This article does not cite any references or sources. ... For the Beck song, see Nausea (song). ... Vomiting (also throwing up or emesis) is the forceful expulsion of the contents of ones stomach through the mouth and sometimes the nose. ... This article or section does not cite its references or sources. ... Trypanophobia is the extreme and irrational fear of medical procedures involving injections or hypodermic needles. ... The English suffix -phobia is used to describe fear or hatred (the latter is often ignored) of a particular thing or subject. ... This article or section is in need of attention from an expert on the subject. ...

Features

People with vasovagal syncope typically have recurrent episodes, usually when exposed to a specific trigger. The initial episode often occurs when the person is a teenager, then recurs in clusters throughout his or her life. Prior to losing consciousness, the individual frequently experiences a prodrome of symptoms such as lightheadedness, nausea, sweating, ringing in the ears, and visual disturbances. These last for at least a few seconds before consciousness is lost, which typically happens when the person is sitting up or standing. When they pass out, they fall down; and when in this position, effective blood flow to the brain is immediately restored, allowing the person to wake up. In medicine, a prodrome is an early symptom indicating the development of a disease, or indicating that a disease attack is imminent. ... For the Beck song, see Nausea (song). ...

The autonomic nervous system's physiologic state (see below) leading to loss of consciousness may persist for several minutes, so: This article or section is in need of attention from an expert on the subject. ...

1. if the person tries to sit or stand when they wake up, they may pass out again; and
2. the person may be nauseated, pale, and sweaty for several minutes after they wake up.

Pathophysiology and mechanism

Regardless of the trigger, the mechanism of syncope is similar in the various vasovagal syncope syndromes. In it, the nucleus tractus solitarius of the brainstem is activated directly or indirectly by the triggering stimulus, resulting in simultaneous enhancement of parasympathetic nervous system (vagal) tone and withdrawal of sympathetic nervous system tone. The solitary nucleus and tract are structures in the brainstem that carry and receive visceral sensation and taste from the facial (VII), glossopharyngeal (IX), vagus (X) cranial nerves, as well as the cranial part of the accessory nerve (XI). ... The brain stem is the stalk of the brain below the cerebral hemispheres. ... Autonomic nervous system innervation, showing the sympathetic and parasympathetic (craniosacral) systems, in red and blue, respectively The parasympathetic nervous system is one of three divisions of the autonomic nervous system. ... The vagus nerve (also called pneumogastric nerve or cranial nerve X) is the tenth of twelve paired cranial nerves, and is the only nerve that starts in the brainstem (within the medulla oblongata) and extends, through the jugular foramen, down below the head, to the abdomen. ... Grays FIG. 838– The right sympathetic chain and its connections with the thoracic, abdominal, and pelvic plexuses. ...

This results in a spectrum of hemodynamic responses:

1. On one end of the spectrum is the cardioinhibitory response, characterized by a drop in heart rate. The drop in heart rate leads to a drop in blood pressure that is so severe that consciousness is lost. It is thought that this response results primarily from enhancement in parasympathetic tone.
2. 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.
3. 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. This reflex involves a variety of cardiovascular and neurological processes, which can be summarized as follows: Prolonged upright posture results in some degree of pooling of blood in the lower extremities that can lead to diminished intracardiac volume. This phenomenon is accentuated if the individual is dehydrated. The resultant arterial hypotension is sensed in the carotid body baroreceptors, and afferent fibers from these receptors trigger autonomic signals that increase cardiac rate and contractility. However, pressure receptors in the wall and trabeculae of the underfilled left ventricle may then sense stimuli, indicating high-pressure C-fiber afferent nerves from these receptors. They may respond by sending signals that trigger paradoxical bradycardia and decreased contractility, resulting in additional and relatively sudden arterial hypotension. ^[1] The blood vessels are part of the circulatory system and function to transport blood throughout the body. ... Grays FIG. 838– The right sympathetic chain and its connections with the thoracic, abdominal, and pelvic plexuses. ... Baroreceptors (or baroceptors) in the human body detect the pressure of blood flowing though them, and can send messages to the central nervous system to increase or decrease total peripheral resistance and cardiac output. ... In nervous systems, afferent signals or nerve fibers carry information toward the brain. ... A trabecula (plural trabeculae) is a small, often microscopic, tissue element in the form of a small beam, strut or rod, generally having a mechanical function, and usually but not necessarily composed of dense collagenous tissue. ...

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. Also is pertinent to differenciate lightheadedness, vertigo and hypoglycemia as other causes This article or section does not cite its references or sources. ...

In patients with recurrent syncope, diagnostic accuracy can often be improved with one of the following diagnostic tests:

1. A tilt table test
2. Implantation of an insertable loop recorder
3. A Holter monitor or event monitor
4. An echocardiogram
5. An electrophysiology study

A tilt table test is a medical procedure often used to diagnose dysautonomia or syncope. ... Holter monitor In medicine, a Holter monitor (also called an ambulatory electrocardiography device), named after its inventor, Dr. Norman J. Holter, is a portable device for continuously monitoring the electrical activity of the heart for 24 hours or more. ... The echocardiogram is an ultrasound of the heart. ... An electrophysiologic study (EPS) is one of a number of tests of the electrical conduction system of the heart performed by a cardiac electrophysiologist, a specialist in the electrical conduction system of the heart. ...

Prognosis

Vasovagal syncope is rarely life-threatening in itself, but may be associated with injury from falling.

Treatment

Treatment for vasovagal syncope focuses on avoidance of triggers, restoring blood flow to the brain during an impending episode, and measures which interrupt or prevent the pathophysiologic mechanism described above.

• The cornerstone of treatment is avoidance of triggers known to cause syncope in that person. Before known triggering events, the patient may increase consumption of salt and fluids to increase blood volume. Sports drinks, such as Gatorade, may be particularly helpful.

• Discontinuation of medications known to lower blood pressure may be helpful, but stopping antihypertensive drugs can also be dangerous. This process should be managed by an expert.

• 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 (for instance, the cause of pain).

• 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.

• Certain medications may be helpful, but are rarely effective by themselves:
  • Beta blockers (β-adrenergic antagonists) are the most common medication given. They work by lessening myocardial contractility, the sudden increase in the force with which the heart pumps.
  • Other medications which may be effective include fludrocortisone, midodrine, SSRIs such as paroxetine or sertraline, and disopyramide.

• For people with the cardioinhibitory form of vasovagal syncope, implantation of a permanent pacemaker may be beneficial or even curative.

Gatorade logo Gatorade is a non-carbonated sports drink marketed by the Quaker Oats Company, a division of PepsiCo. ... Antihypertensives are a class of drugs that are used in medicine and pharmacology to treat hypertension (high blood pressure). ... In medicine, a prodrome is an early symptom indicating the development of a disease, or indicating that a disease attack is imminent. ... A medication is a drug or substance taken to reduce symptoms or cure an illness or medical condition. ... Beta blockers or beta-adrenergic blocking agents are a class of drugs used to treat a variety of cardiovascular conditions and some other diseases. ... Fludrocortisone acetate is a synthetic corticosteroid with moderate glucocorticoid potency and much greater mineralocorticoid potency. ... Midodrine is an alpha-sympathomimetic drug. ... SSRI is an acronym that stands for several things: It is a class of antidepressants called selective serotonin reuptake inhibitor SSRI also is used as the stock symbol for Silver Standard Resources Inc. ... Paroxetine or paroxetine hydrochloride is a selective serotonin reuptake inhibitor (SSRI) antidepressant. ... “Lustral” redirects here. ... A pacemaker A pacemaker (or artificial pacemaker, so as not to be confused with the hearts natural pacemaker) is a medical device designed to regulate the beating of the heart. ...

Cultural References

In the episode My Perspective of the television show Scrubs, J.D. is diagnosed with Vasovagal Syncope triggered by defecation. My Perspective is the 126th episode of the American situation comedy Scrubs. ...

References

• Daroff, Robert B. & Carlson, Mark D. (2001). Faintness, Syncope, Dizziness, and Vertigo. In Eugene Braunwald, Anthony S. Fauci, Dennis L. Kasper, Stephen L. Hauser, Dan L. Longo, & J. Larry Jameson (Eds.), Harrison's Principles of Internal Medicine (15th Edition), pp. 111–115. New York: McGraw-Hill these can stand to be attributed with other sources as well.

External links

• Dysautonomia Information Network
• Dysautonomia Youth Network of America, Inc.
• Seattle Community Network Autism information
• Dysautonomia Support Network
• Tilt table test