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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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[beta]-Blockers no better than placebo in the treatment of vasovagal syncope - Patient-Oriented Evidence that Matters
From Journal of Family Practice, 11/1/02 by John Phillips

Flevari P. Livanis EG, Theodorakis GN, Zarvalis E. Mesiskli T, Kremastinos DT. Vasovagal syncope: a prospective, randomized, crossover evaluation of the effect of propranolol, nadolol, and placebo on syncope recurrence and patients' well-being. J Am Coll Cardiol 2002; 10:499-504.

* BACKGROUND About half of syncopal episodes are vasovagal reactions. Empiric treatment with [beta] blockers is a common practice based on physiologic mechanisms of vasovagal syncope. Only 3 prospective, randomized controlled trials have been done to compare a [beta]-blocker (atenolol) with placebo; no study showed reduced syncopal episodes. No studies have been published on [beta]-blockers other than atenolol.

* POPULATION STUDIED The authors enrolled 30 consecutive patients with recurrent vasovagal syncope. The mean age of the subjects was 41 years; 17 (57%) were women. Investigators defined recurrent vasovagal syncope as at least 2 episodes in the past 3 months and a positive tilt test response. Patients had normal cardiovascular examinations and no electrocardiographic changes. Patients were excluded who had known or suspected autonomic failure (including diabetes), hypertension, chronic obstructive pulmonary disease, or peripheral vascular disease. Patients were recruited from an outpatient cardiology setting, potentially representing a different population than encountered in many primary care settings.

* STUDY DESIGN AND VALIDITY This study was an unblinded, crossover placebo-controlled trial. Patients were assigned to receive 3 drugs in random order for 3 months each. Study drugs were the maximum tolerated dose of propranolol (Inderal) 20 to 40 mg 3 times daily, nadolol (Corgard) 40 to 80 mg once daily, and placebo 1 capsule once daily. Investigators were not blinded but patients were. However, patients took propranolol 3 times daily compared with once daily for placebo and nadolol. To minimize the effect of dosing frequency, investigators advised patients that frequency had no relationship with efficacy. Concealed allocation was not performed. All 30 patients completed the study, although 1 patient withdrew from propranolol therapy due to fatigue. Results were analyzed by intention to treat.

This study is sufficiently well done to allow conclusions on the efficacy of the 2 [beta]-blockers versus placebo. A power calculation was not performed. although the crossover design significantly increases power by having each patient serve as his or her own control. Failure to double-blind and to use concealed allocation typically compromises a study's validity. However, such flaws usually increase the effect of the experimental treatment. Because no statistically significant differences between placebo and treatment groups were found in this study, these study design limitations are of less concern.

* OUTCOMES MEASURED The primary outcome measured was the number of syncopal and presyncopal events during each study drug's 3-month period. Additionally, patients' assessed their quality of life and reported which therapies they preferred. Quality of life was scored from 0 to 4 based on vasovagal symptoms, drug side effects, and personal well being during therapy (0 = very dissatisfied and 4 = excellent).

* RESULTS Overall, no difference was noted in the number of syncopal episodes or quality of life scores during the 3 study periods. Propranolol, nadolol, and placebo equally improved outcomes as compared with baseline (0.25, 0.25, and 0.5 episodes during 3 months respectively vs 3.4 episodes per 3 months; P < .0001). Similar benefits were seen for presyncopal episodes (2.1, 1.3, and 2.6 episodes during 3 months, respectively vs 9.1 episodes per 3 months; P < .0001). Patients' quality of life scores improved with propranolol, nadolol, and placebo as compared with baseline (3.1. 3.5, and 3.4 on a scale of 4, respectively vs 1.5; P < .0001). At the conclusion of the study, 4 patients preferred nadolol, 2 preferred placebo, and 3 preferred propranolol. Five patients were dissatisfied with propranolol due to fatigue. The remaining 70% of patients were satisfied with all 3 regimens.


Most patients with vasovagal syncope had a profound response to [beta]-blocker therapy with a marked decrease in episodes during a 3-month period. However, the patients had a similar response when treated with placebo. Because we do not use placebos frequently in practice and no other therapies have proven benefit above the placebo response, dosing with a [beta]-blocker, if well tolerated, is an option for treating this type of syncope.

COPYRIGHT 2002 Dowden Health Media, Inc.
COPYRIGHT 2002 Gale Group

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