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Neurocardiogenic Syncope - a Common Cause of Fainting Examined

written by: Cordie Kellerman • edited by: Leigh A. Zaykoski • updated: 11/27/2009

Neurocardiogenic syncope, also known as simple fainting, is caused when the heart does the right thing at the wrong time.

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    In laymen's terms, syncope is a fainting episode (a loss of consciousness). Neurocardiogenic syncope references the cause of fainting, which is a sudden drop in blood pressure that results in a reduction of blood flow to the brain. Also known as a simple faint, vasovagal syncopy and neurally mediated syncope, it can occur in people with no known heart or neurological conditions.

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    Loss of consciousness (fainting) is the defining symptom and most often occurs when standing. This frequently involves a change of position from sitting or lying down to standing. The fainting episode may be preceded by other symptoms, such as dizziness (vertigo), headache, nausea, sweating, pale skin, heart palpitations, disorientation, and vomiting. These warning symptoms (if any occur) may be very brief (only seconds) and rarely continue more than a few minutes. Most often, the loss of consciousness is brief as well. Occasionally, some seizure-like activity occurs during the episode, but this does not appear to be related to epilepsy. After the syncopy episode is over, the patient may feel warm and flushed. They may be clammy to the touch and their heart rates are generally slow.

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    This type of fainting episode occurs when some normal mechanisms involving communication between the brain and heart briefly trigger an inadequate, or even incorrect, response to conditions. Two different mechanisms may be involved. The first involves the dilation of blood vessels in the lower extremities and the second involves the heart's response to a drop in blood pressure.

    One way the body responds to high blood pressure is to dilate blood vessels, but blood vessels may also become dilated when blood begins to pool in the legs (from long periods of standing, for example). This is just a normal result of gravity, but with the extra volume of blood in the legs, there is less available for the brain. The brain's appropriate response is to signal the heart to increase its pumping action and move more blood to the brain. However, it appears that sometimes when this happens, receptors in the heart misinterpret the response as a signal that blood pressure is too high and just as the heart has begun to move more blood to the brain, it is told to slow down. At the same time a signal may also be sent to the vessels in the legs to further dilate in order to help bring blood pressure down further (when in fact, blood pressure is already too low). This brings an even greater drop in blood pressure and less blood flow to the brain, which results in a loss of consciousness.

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    Because there are many other causes of fainting, one of the first things a physician must do is eliminate those other causes. The patient's description of the triggers of the syncope and the specific symptoms may suggest several possibilities. Indicators that neurocardiogenic syncope may be the culprit would be that standing is often involved as well as other activities that would cause vessels to dilate (a hot bath for example). If episodes tend to occur after eating, when digestion requires that more blood be shifted to the digestive system, that suggests a similar mechanism as when blood pools in the legs.

    If the physician's examination of the patient and the patient's history suggest conditions other than neurocardiogenic syncope, then appropriate testing will be done to evaluate their role. If this condition is suggested, then a tilt table test may be ordered. During a tilt table test, the patient's blood pressure and heart rate are monitored as the table moves the patient from a flat (lying down) position to and upright (standing) position.

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    The patient can do a lot to control the condition by learning how to respond to symptoms. If one is feeling faint, they should immediately lie down and elevate their legs. (Very rarely, a fainting patient could die if prevented from lying down.) A patient can increase blood volume by simply increasing fluid intake. Sometimes increasing dietary salt will effectively increase blood pressure and decrease the frequency or severity of symptoms.

    The patient that is alert to emotional and environmental triggers can reduce the frequency and severity of symptoms. They can address emotional stressors, avoid standing in long lines, avoid prolonged exposure to hot environments (hot weather, showers, saunas, etc.). A patient that often must stand for long periods of time may be helped by wearing compression stockings. Avoid alcohol and caffeine because they both cause blood vessels to dilate.

    Medical treatment may be necessary for more persistent cases. Treatments include beta-blockers, ACE inhibitors, calcium channel blockers, serotonin reuptake inhibitors, theophylline, and other drugs. It often takes patience and perseverance on the part of both patient and physician to find the right medication or combination of medications. If medical treatments prove inadequate, sometimes a pacemaker is recommended, but its efficacy is unclear.