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Vasovagal syncope

Vasovagal syncope (also vasodepressor syncope, neurally mediated syncope or neurocardiogenic syncope), a form of dysautonomia, is the most common cause of fainting ("syncope" in medical terminology). Although it is particularly common (both historically and stereotypically) among young women, it is seen across all ages and genders and in otherwise completely healthy people. It is triggered by a number of factors, including prolonged standing, alcohol, fatigue, hunger, and anxiety. more...

VACTERL association
Van der Woude syndrome
Van Goethem syndrome
Varicella Zoster
Variegate porphyria
Vasovagal syncope
VATER association
Velocardiofacial syndrome
Ventricular septal defect
Viral hemorrhagic fever
Vitamin B12 Deficiency
VLCAD deficiency
Von Gierke disease
Von Hippel-Lindau disease
Von Recklinghausen disease
Von Willebrand disease

Vasovagal syncope is caused by low heart rate and blood pressure, leading to inadequate circulation. The reduced oxygen supply to the brain results in syncope, or temporary loss of consciousness. Individuals usually regain consciousness within a few minutes and their prognosis is good, although the syncope has a tendency to recur.


Prior to losing consciousness, the individual usually experiences symptoms such as nausea, inability to hear properly, difficulty speaking, exhaustion, tightness in the throat and blurry vision. Sweatiness and dizziness are also very common. These symptoms may last anywhere from seconds to minutes. This is followed by an episode of fainting; the individual regains consciousness within seconds to minutes. It is uncommon for vasovagal syncope to occur while the individual is lying down (supine); it normally occurs while standing or sitting.

During the episode, the individual will be unresponsive, and the pulse and blood pressure will be low. In some cases the individual may react violently while unconscious, this may be due to a fear response and increased adrenaline. The reaction may have the appearance of a seizure. Upon regaining consciousness, the individual may appear flushed and feel generally lethargic. The heart rate may still be slow, although it soon returns to normal.


In addition to vasovagal syncope, a number of other medical conditions may cause fainting. It is essential to perform a thorough history (interview of the patient) and physical examination. If there is no sign of other medical problems or causes of fainting, and the patient's description is consistent with or suggestive of vasovagal syncope, no diagnostic testing may be necessary. However, if the fainting is recurrent, a tilt table test is usually performed. In this test, the patient lies flat on a table and is then tilted upright so that blood pressure and heart rate may be observed and measured to identify any severe changes. This test is particularly effective in identifying patients suffering from sensitive nervous systems. Depending on the physician's level of suspicion, other tests, including an electrocardiogram, may be performed.


Vasovagal syncope is due to a disorder of autonomic control of the cardiovascular system. It commonly occurs in normal people of all ages. Precipitating factors include alcohol consumption, fatigue, pain, hunger, and prolonged standing. It can also be triggered by situations causing anxiety, such as having blood drawn, as well as by hot or crowded situations.

The initial responses appear to be venous pooling and increased activity of the sympathetic nervous system. This causes the heart to contract forcefully while relatively empty, triggering ventricular mechanoreceptors and vagal nerve fibers. This has the effect of reducing sympathetic activity while stimulating parasympathetic activity, resulting in bradycardia and vasodilation, followed by syncope.


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Action stat: Vasovagal syncope
From Nursing, 7/1/03 by Chiocca, Ellen M

KELLY WEBER, 15, arrives in your ED early one Saturday morning, accompanied by her mother. Half an hour ago, she began to feel light-headed and dizzy. Losing consciousness for about 30 seconds, she fell and hit her head on a coffee table. She was alert when she regained consciousness, and now says she feels fine. Kelly's mother is concerned because in the last month, Kelly has fainted twice at school, once during gym class, but recovered quickly after resting and drinking fluids.

What's the situation?

Kelly is alert, oriented, and in no appar- ent distress. You observe a small laceration and contusion on her forehead. Her vital signs are: BP, 108/68; pulse, 76; respirations, 22; temperature, 98.9 deg F (37.2 deg C); and Spo^sub 2^, 99% on room air. A fingerstick glucose reading is 108 mg/dl. Kelly has no history of seizures, migraines, diabetes, or congenital heart disease. She denies drug or alcohol use and takes no medications. Her menses began 3 days ago.

Kelly's mother denies that Kelly had cyanosis, tonicclonic movements, or urinary incontinence during the episode. She's of normal weight with no history of an eating disorder.

What's your assessment?

You suspect that Kelly experienced a vasovagal syncope episode, also known as fainting. When a person sits or stands, blood pools in the legs. Heart rate and vasoconstriction should push blood back to the heart, but in vasovagal syncope, the heart rate slows and vessels dilate instead, causing hypotension and cerebral hypoperfusion. The person may fall, but usually regains consciousness immediately after becoming recumbent.

Syncope can occur with or without a prodrome that may last for seconds to minutes; symptoms may include nausea, light-headedness, and dizziness.

Syncope can result from disorders of vascular tone or blood volume, cardiovascular disorders (including arrhythmias), cerebrovascular disease, or metabolic or psychogenic causes. In children and adolescents, syncope is most commonly vagally mediated.

What must you do immediately?

Listen to Kelly's heart for at least 1 full minute, noting the rate, rhythm, and presence of any murmurs. Obtain a 12-lead ECG, noting any rhythm disturbances, conduction abnormalities, or QT-interval prolongation. Measure Kelly's BP and pulse again in the lying, sitting, and standing positions, to determine whether she has orthostatic hypotension. Perform a neurologic assessment.

Obtain blood samples for complete blood cell count (to detect anemia) and chemistry profile (to reveal hypoglycemia or electrolyte imbalances), as ordered. Clean and dress Kelly's head wound.

What should be done later?

Kelly's vital signs and diagnostic tests are normal, so she'll be discharged from the ED. Because she's fainted twice before, including during physical activity, she'll need further diagnostic tests to determine the cause of her syncope. These tests might include a tilt-table test, an electroencephalogram, imaging studies of the brain and heart, or a 24-hour cardiac event recorder. Tell her not to participate in gym class until she sees her primary care provider for evaluation.

If Kelly has vasovagal syncope, her health care provider will recommend that she avoid dehydration by increasing her fluid and sodium intake and avoiding beverages that contain caffeine. She should eat small, frequent meals. If these measures aren't effective alone, she may need medications such as fludrocortisone, which causes sodium retention and helps prevent dehydration and hypotension. Beta-blockers such as atenolol also may be ordered to prevent large variations in heart rate.


Assistant Professor of Clinical Nursing * Coordinator, Pediatric Nurse Practitioner Program * Loyola University Chicago - Chicago, Ill.

Copyright Springhouse Corporation Jul 2003
Provided by ProQuest Information and Learning Company. All rights Reserved

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