Neurocardiogenic and Non-Cardiovascular Syncope

There are many types of syncope that have non-cardiovascular causes.

Neurocardiogenic syncope

Neurocardiogenic syncope - the "common faint" - also is called "vasovagal syncope." It usually (but not always) occurs when a person who is lying or sitting down moves to a standing position. From 25 percent to 40 percent of fainting disorders are due to neurocardiogenic syncope.

This type of syncope often affects young, healthy people who have no history of heart disease or neurological problems. It is generally thought to result from a "miscommunication" between the brain and the heart or an exageration of a normal reflex.

When we stand up, our brains send signals telling the blood vessels in our legs to dilate, or open wider. Often, a signal also is sent that slows the heartbeat. When the blood vessels suddenly dilate, blood may pool in the legs so that a normal volume of blood does not return to the heart. If the heart does not pump enough blood to supply the brain's need for oxygen, we become lightheaded or faint.

Sometimes, the heart tries to raise the blood pressure by increasing the force and rate of its muscle contractions. This makes the problem worse:

• As the heart beats faster and stronger, it sends a wrong message that tells receptors in the heart's chambers that the ventricle is filled with blood.
• The receptors send a message telling the nervous system that blood pressure is too high. In fact, the ventricle is not full and the blood pressure is too low.
• When the brain receives the faulty message, it slows the heart rate and further dilates the blood vessels.
• The blood pressure drops even lower, less blood is pumped to the brain and the risk of fainting increases.

Neurocardiogenic syncope is the most common cause of fainting in young people. Some adolescents have frequent fainting spells, but many electrophysiologists and other physicians who treat syncope report that most of their young patients have "grown out" of the condition by the time they reach their mid-twenties.

Other Types of Non-Cardiovascular Syncope

• What is Dysautonomia? A number of physical problems - including some types of fainting - are due to problems in the autonomous nervous system (ANS). This is the system that automatically manages many of our bodily functions, including blood pressure and heart rate. It also controls how we react to fear, anxiety and emotional stress. If something goes wrong with the ANS, it is called dysautonomia.

  Postural tachycardia syndrome (POTS) is considered a type of neurocardiogenic syncope. It is characterized by a very fast heartbeat (tachycardia) that occurs when a person stands up. Some cases of chronic fatigue syndrome may be related to this condition.
• Neurological syncope usually is caused by seizure disorders, such as epilepsy, Parkinson's and other problems of the nervous system.

Orthostatic hypotension and orthostatic intolerance - an inability to maintain normal blood pressure while standing - often are due to disorders of the autonomous nervous system (ANS), which regulates most "automatic" bodily functions. It may occur in otherwise healthy people as a result of standing for long periods, exercise, overheating or other forms of stress. Conditions that affect the nervous system, such as diabetes, Parkinson's, multiple sclerosis or age-related nerve damage may contribute to the condition.

• Psychogenic syncope refers to fainting spells related to anxiety, panic or major depression.
• Metabolic syncope results from problems such as low blood sugar (hypoglycemia) or hyperventilation (shallow, rapid breathing).

Non-cardiovascular syncope may be triggered by a number of factors, such as:

• Any condition that causes low blood pressure.
• A severe reduction in blood volume caused by bleeding, diarrhea or vomiting.
• Eating a meal or drinking alcohol (fainting after a meal is called postprandial syncope.)
• Vigorous exercise.
• Overheating, dehydration or loss of salt from the body.
• Medications such as diuretics that cause fluid loss. Doctors sometimes prescribe diuretics to control blood pressure.
  If too much fluid is lost, however, fainting may result.
• Menstruation. Some young women have fainting spells around the time of their menstrual period. These may disappear and then return during or immediately after pregnancy.
• A "hypersensitive" autonomous nervous system. Some people faint frequently in response to a variety of triggers such as sneezing, coughing, urinating, having a bowel movement.
• Emotional or stressful situations, depression, panic attacks or anxiety.
• Headache
• Illness or trauma