Gourt Home::Gourt :: 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). It is important to realize that vasovagal syncope and vasodepressor syncope are NOT the same. Vasodepressor syncope may cause long-term symptoms of nausea, fatigue, "wooziness" or dizziness, etc. Although it is particularly common (both historically and stereotypically) among young women and men, 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. 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.
Features
Prior to losing consciousness, the individual usually experiences symptoms such as nausea, sweatiness, dizziness, auditory impairment, aphasia, exhaustion, tightness in the throat and blurry vision (visually, one may also see "black spots", colors may go greyish, black at the corner of the eyes, inability to focus). 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 fairly uncommon for vasovagal syncope to occur while the individual is sitting and extremely rare when he/she is lying down (supine); non-standing syncope should point to causes other than vasovagal.
During the episode, the individual will be unresponsive, and the pulse will be high as the 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, feel generally lethargic, and may seem very postictal. The heart rate may still be fast, although it usually soon returns to normal.
Diagnosis
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.
Pathophysiology
Vasovagal syncope is caused by an exaggerated response of the normal autonomic system on 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 reduces sympathetic activity and stimulates parasympathetic activity, resulting in bradycardia and vasodilation, followed by fainting. This mechanism is probably not the only explanation, as some inciting factors, such as hunger or anxiety, do not involve venous pooling. Patients with non-innervated transplanted hearts also exhibit episodes resembling those of vasovagal syncope.
The prognosis is usually good, although prolonged hypotension or asystole may cause damage. In addition, if syncope occurs without warning, injury may occur as a result of falling. Vasovagal syncope is often recurrent and may require treatment.
Treatment
Treatment for vasovagal syncope focuses on restoring blood flow during an episode and on prevention of future episodes.
Patients should be educated on how to respond to further episodes of syncope, especially if they experience warning signs (a "prodrome"). They should lie down 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, to improve blood flow to the heart and brain. If the inciting factor is known, it should be removed if possible (for instance, the cause of pain).
The primary method of prevention is lifestyle modification: the patient should attempt to avoid situations known to cause syncope. Before known triggering events, the patient may increase consumption of salt and fluids to increase blood volume. Sports drinks, such as Gatorade, can be particularly helpful.
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 include disopyramide, paroxetine (Paxil), transdermal scopolamine, and midodrine. Patients who suffer adverse reactions to beta blockers are often prescribed drugs such as Clonidine hydrochloride, which increase blood flow. While not as effective as Beta blockers, they significantly reduce the duration and frequency of syncope.
For repeated episodes of vasovagal syncope or those that cause the heart to stop for a long time (prolonged asystole), a pacemaker may need to be implanted. The pacemaker monitors the heartbeat and will trigger a heartbeat if too long an interval passes between beats.
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
External links
"Vasovagal syncope"