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Vasovagal Syncope

Vasovagal Syndrome

A vasovagal syncope is loss of consciousness associated with vagal activity. It may be triggered by pain, fright, stress, dehydration or trauma.


Before losing consciousness, some of the early signs and symptoms presented by vasovagal syncope patients include lightheadedness, nausea, extremely high or extremely low body temperature (often followed by sweating), tinnitus, palpitations, confusion, a slight inability to speak, often followed by mild stuttering, nervousness and visual disturbances are other symptoms that can occur as well [8].

The symptoms often last for a few seconds before the loss of consciousness begins. The loss of consciousness often happens when the individual is sitting up or standing. As soon as the sufferer passes out, they fall down. At this point blood flow to the brain is restored instantaneously. A seizure may result if the individual doesn’t fall into a fully flat supine position and the head stays elevated above the trunk as blood will unable to quickly return to the brain. 

  • These new data seem to indicate that some unexplained falls could be cases of atypical VVS/carotid sinus syncope with retrograde amnesia.[ncbi.nlm.nih.gov]
  • As soon as the sufferer passes out, they fall down. At this point blood flow to the brain is restored instantaneously.[symptoma.com]
  • Synonym(s): vasodepressor syncope. vasovagal syncope See FAINTING. syncope a temporary suspension of consciousness due to cerebral anemia; fainting. cardiac syncope sudden loss of consciousness due to cerebral anemia caused by ventricular asystole, extreme[medical-dictionary.thefreedictionary.com]
  • Mild blood loss, poor physical condition, prolonged bed rest, anemia, fever, organic heart disease, and fasting are other factors which increase the possibility of fainting in susceptible individuals.[healthcentral.com]
  • Susceptible individuals may be especially prone to these fainting episodes if any of the following conditions are present: mild blood loss; anemia; fever; hypoglycemia; or injury.[diversalertnetwork.org]
  • Your doctor may look for conditions, such as anemia, that can cause or contribute to fainting spells. Tilt table test If no heart problems appear to cause your fainting, your doctor may suggest you undergo a tilt table test.[mayoclinic.org]
  • Children with VVS had symptoms of dizziness, pallor, blurred vision, nausea, and some had syncope. Erythrocyte H2S production was measured by a sulphur-sensitive electrode.[ncbi.nlm.nih.gov]
  • Clinical findings Abrupt loss of vascular tone; nausea; diaphoresis; pallor.[medical-dictionary.thefreedictionary.com]
  • The onset may be abrupt or gradual and is often associated with warning symptoms such as lightheadedness, dizziness, weakness, feeling hot or cold, fatigue, nausea, abdominal pain, sweating, pallor, visual disturbances or confusion.[pccoforegon.com]
  • In the second to minutes leading up to the fainting, the patient may feel weakness, nausea, pallor, and sweating.[courses.washington.edu]
  • MATERIAL AND METHOD: In this open-label, randomized controlled study, we used the Italian tilt protocol, namely 60 degree passive tilting followed by 0.4 mg nitroglycerin challenge when the passive phase fails to induce syncope.[ncbi.nlm.nih.gov]
  • Presyncopal (near fainting) patients may also complain of vomiting, disorientation, and difficulty speaking or seeing.[pccoforegon.com]
  • , especially on hot days, or if you have been exercising or have had diarrhoea or vomiting. Your urine should be clear.[jpaget.nhs.uk]
  • A 48-YEAR-OLD WOMAN with a history of syncopal events was brought to the emergency department (ED) by her daughter, following an episode in which the mother lost consciousness and vomited while driving.[mdedge.com]
  • U of Washington Study (2) Of those having symptoms Feeling of faintness or dizziness (85%) Nausea (50%) Feeling hot (31%) or cold (21%) Pallor (79%) Sweating (57%) Vomiting or loss of consciousness (0%) Pavlin, et. al. (1993) 16.[slideshare.net]
  • POTS has recently been conflated with VVS when excessive tachycardia is succeeded by hypotension during tilt testing.[ncbi.nlm.nih.gov]
Orthostatic Hypotension
  • Both types of syncope are associated with orthostatic hypotension and are nonlethal. The underlying pathophysiology manifests the vast symptoms suffered by the individual.[ncbi.nlm.nih.gov]
  • The highest recommended dose for orthostatic hypotension is 0.3 mg daily. The dose range in this study was 0.05-0.2 mg daily, so some patients may have been underdosed.[reliasmedia.com]
  • Orthostatic Hypotension (2) Treatment Lie down Trendelenberg position NS Regulate medications 24.[slideshare.net]
  • A 16-year-old healthy boy had sometimes experienced dizziness when looking at the tips of pens. When he put his finger and the lens close to his eye to insert a soft contact lens, he felt sick and dizzy and fell unconscious.[ncbi.nlm.nih.gov]
  • It is also important for patient’s to recognize the feeling of dizziness so that they can react appropriately to their body's signals and either sit or lie down quickly. Once the dizziness has passed, they can slowly stand up again.[pediatricheartspecialists.com]
  • This causes blood pressure to fall and dizziness as less blood goes to the brain. This is usually relieved by lying down. Vasovagal syncope is not dangerous and usually gets better in time.[newcastle-hospitals.org.uk]
  • When the blood flow to your brain decreases you will most likely become faint or dizzy and you can become unconscious.[gazettereview.com]
  • As soon as there is a slow-down in heart rate, the resulting lack of blood to the brain brings about fainting and confusion.[symptoma.com]
  • They may complain of symptoms including nausea, abdominal pain, clamminess, tremors, lightheadedness, headache, malaise, exhaustion and confusion.[pccoforegon.com]
  • After "blacking out," the person usually regains consciousness within minutes, but may experience a period of confusion or feeling weak for up to 24 hours. In 2002, former U.S. President George W.[cnn.com]
  • However, these fainting spells can be accompanied by confusion, jerking movements and loss of consciousness much like an epileptic seizure. At times, patients’ pupils may dilate and be noticed by others prior to fainting.[rscdiagnosticservices.com]
  • On two occassions I woke up at end of seizure and experienced a hellish state of confusion, random thoughts and fear that cannot be matched by any other experience.[epilepsy.com]
  • It is very important to differentiate vertigo, seizures, light-headedness, seizures, vertigo and hypoglycaemia as other causes.[symptoma.com]
  • It is pertinent to differentiate lightheadedness, seizures, vertigo, and low blood sugar as other causes.[en.wikipedia.org]
  • It has many causes, and is distinct from vertigo, seizures, coma, falls, psychogenic pseudosyncope, drop attacks, transient ischaemic attacks, and states of altered consciousness. [3] Strickberger SA, Benson DW, Biaggioni I, et al.[bestpractice.bmj.com]
Drop Attacks
  • Autonomic failure 8.1.2 Epilepsy and ictal asystole 8.1.3 Cerebrovascular disorders 8.1.4 Migraine 8.1.5 Cataplexy 8.1.6 Drop attacks 8.2 Neurological tests 8.2.1 Electroencephalography 8.2.2 Brain computed tomography and magnetic resonance imaging 8.2.3[escardio.org]
  • It has many causes, and is distinct from vertigo, seizures, coma, falls, psychogenic pseudosyncope, drop attacks, transient ischaemic attacks, and states of altered consciousness. [3] Strickberger SA, Benson DW, Biaggioni I, et al.[bestpractice.bmj.com]
  • Drop attacks. Dizziness or vertigo without loss of consciousness. Alcohol/drug abuse. Transient ischaemic attacks / stroke. Psychogenic pseudosyncope. See also separate Dizziness, Giddiness and Feeling Faint article.[patient.info]
  • attacks” that occur with little warning.[circ.ahajournals.org]
  • Venlafaxine 75 mg XR form PO QD or BID Nausea, anorexia, hypertension Paroxetine * 10 mg PO QD Nausea, tremor, diarrhea, agitation Erythropoietin 8000 IU SC once per week Requires injections, burning at site, increased hematocrit, CVA Metoprolol * 25[circ.ahajournals.org]


There are many medical conditions that may cause syncope. This is why making the correct diagnosis for loss of consciousness is one of the most difficult challenges facing health care providers. The core of the diagnosis of vasovagal syncope is dependent on a clear description by the patient for a particular pattern of triggers and time course. It is very important to differentiate vertigo, seizures, light-headedness, seizures, vertigo and hypoglycaemia as other causes.

For patients with recurring vasovagal syncope, the accuracy of diagnosis can often be improved with any one of the following diagnostic tests [9]:

  • Tilt table test
  • Echocardiogram
  • Holter monitor or event monitor
  • Implantation of an insertable loop recorder
  • Electrophysiology study
Epileptiform Activity
  • However, continuous electroencephalogram, blood pressure, and heart rate recordings during attacks indicated that in some episodes there was neither cardiovascular change nor epileptiform activity, implying feigned syncope (pseudosyncope) with pseudoseizures[ncbi.nlm.nih.gov]
Chloride Increased
  • Fludrocortisone and sodium chloride increase systemic fluid volume. Midodrine, β blockers and norepinephrine transport inhibitors modulate the sympathetic nervous system.[ncbi.nlm.nih.gov]
Sinus Arrest
  • Vasovagal syncope with concomitant ventricular asystole and sinus arrest is rare. Aggressive management with permanent pacemaker is strongly advocated in malignant vasovagal syncope.[ncbi.nlm.nih.gov]
  • Facts While standing, approximately 300-700 ml of blood pools in the lower extremities which decreases intravascular volume Strong vagal stimulations may induce 4-10 seconds of sinus arrest 15 seconds of asystole is necessary to produce unconsciousness[slideshare.net]


  • Applied tension is a behavioral treatment approach that has been demonstrated to be efficacious for the treatment of vasovagal syncope associated with injection phobia.[ncbi.nlm.nih.gov]


  • VVS in patients with LV dysfunction may be refractory to treatment and could be associated with poor prognosis. KEYWORDS: Autonomic nervous system; Head-up tilt; Left ventricular dysfunction; Vasovagal syncope[ncbi.nlm.nih.gov]
  • All aspects of VVS are covered, including epidemiology, pathophysiology, diagnosis and differential diagnosis, prognosis, therapy and implications for particular activities such as work, driving and physical activity.[springer.com]
  • Short- and long-term prognosis of syncope, risk factors, and role of hospital admission: results from the STePS (Short-Term Prognosis of Syncope) study. J Am Coll Cardiol. 2008 Jan 22. 51(3):276-83. [Medline]. Andrea U, Attilio DR, Franco G, et al.[medscape.com]
  • Prognosis [ edit ] This section needs expansion.[en.wikipedia.org]


Vasovagal syncope often occurs in response to a trigger and there is often a corresponding malfunction in the parts of the nervous system which regulate the heart rate and blood pressure [4]. As soon as there is a slow-down in heart rate, the resulting lack of blood to the brain brings about fainting and confusion.

Below are some of the main triggers for vasovagal episodes:

  • Sensitivity as a result of pain
  • Extreme menstural pains
  • Pressure on the chest after heavy exercising
  • Being present during medical procedures
  • Sight of blood
  • Biopsy procedures (pre and post)
  • Increased stress levels
  • Dehydration
  • Ingestion of certain medications and addcitive substances
  • Heavy emotional swings
  • Nervous malfucntions
  • In rare cases, low sugar level in blood


The incidence for this condition is 6.2 cases per 100 patient years in the United States [5]. Syncope also reoccurs in less than 3% of affected individuals and also, 10% of affected individuals have a cardiac etiology. Data from around the world also suggest a similar occurrence rate to what is obtainable in the United States.

Sex distribution
Age distribution


Vasovagal syncope occurs as a result of cerebral hypoperfusion [6]. Brain parenchyma is dependent on sustained blood flow to be able to provide a constant supply of glucose which is its major metabolic substrate. It is not possible for the brain tissue to store energy in form of high-energy phosphates as is seen in other areas of the body. This is why cerebral perfusion of between 3 to 5 seconds is enough to bring about syncope.

Cerebral perfusion is maintained relatively constant by an intricate and complex feedback system which typically involves arterial pressure, intravascular volume status, metabolic regulation and cerebrovascular resistance with intrinsic autoregulation. When there is a significant defect in any of these or subclinical defects in several of these systems, syncope may arise.


  • Past studies found that an Anti-Gravity suit (G-suit) can increase blood pressure and has been reported to prevent orthostatic hypotension effectively in patients with diabetes. It is possible that the G-suit can prevent VVS.[ncbi.nlm.nih.gov]


Syncope refers to a self-limited loss of consciousness accompanied by the inability to maintain postural tone. Most of the time, it is followed by spontaneous recovery [1]. The condition doesn’t include seizures, coma, shock or other such states of altered consciousness.

There are many recognised etiologies for syncope but categorization is made into reflex (neutrally mediated), orthostatic and cardiac so as to ensure proper initial evaluation [2]. Cardiac vasovagal syncope has the highest number of mortality while non-cardiac syncope doesn’t have such high mortality. Syncope can result in significant morbidity due to accidents or falls that may occur following its onset [3].

Patient Information

Vasovagal syncope refers to one of the most common causes of fainting. It occurs when the body begins to overreact to certain triggers. The most common triggers are sight of blood and extreme emotional distress.

The vasovagal syncope trigger kicks off a sudden drop in heart rate and blood pressure. This brings about a reduction in blood flow to the brain which leads to a momentary loss of consciousness.

The condition is often harmless requiring no treatment. However, it is possible for patients to get injured during an episode of the condition. The doctor may recommend tests to rule out more serious cases of fainting such as an underlying heart condition.

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Last updated: 2019-06-28 11:45