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Syncope, Vasovagal (Fainting)

Definition :
Syncope (commonly referred to as fainting) is a loss of consciousness that occurs when you experience a significant reduction of blood flow to your brain. Fainting is often caused by a significant drop in blood pressure or from a very slow heart rate. The result is a sudden reduction of blood flow to your brain, causing you to lose consciousness.

The most common cause of fainting is due to vasovagal syncope. Vasovagal syncope is triggered by a stimulus that results in an exaggerated and inappropriate response in the part of your nervous system that regulates involuntary body functions, including heart rate and blood flow (autonomic nervous system). When some sort of stimulus triggers this exaggerated response, both your heart rate and blood pressure drop, quickly reducing blood flow to your brain and leading to loss of consciousness. A person who has fainted due to vasovagal syncope recovers quickly, usually within seconds or a few minutes.

Common triggers of vasovagal syncope include standing for long periods, dehydration, the sight of blood, coughing, urination, having a bowel movement and emotional distress. But in some cases, the cause of vasovagal syncope can't be determined.

Fainting is common, and treatment is unnecessary in most cases. However, sometimes fainting can indicate an underlying disease for which you'll need treatment.

Causes :
In order for you to remain conscious, your heart continuously pumps blood to your brain. Fainting due to vasovagal syncope occurs when your autonomic nervous system, the part of your nervous system that regulates heart rate and blood pressure, goes awry — ultimately depriving your brain of this blood supply.

When you experience a fainting trigger, such as the sight of blood, your autonomic nervous system reacts inappropriately by causing your heart rate to slow and the blood vessels in your legs to widen (dilate). Blood then pools in your legs, causing low blood pressure. This drop in blood pressure and slowed heart rate quickly cause diminished blood flow to your brain, and fainting occurs.

Potential triggers are numerous
A number of different stimuli — both emotional and physiological — can trigger vasovagal fainting. The reason behind many of these triggers is unclear. Fainting may be the result of one or more of these Causes:

  • Emotional distress, including panic attacks, anxiety attacks or fear
  • Standing in a hot, crowded area
  • Having a bowel movement (especially if straining)
  • Coughing strenuously
  • Unpleasant situations, such as the sight of blood
  • Urinating
  • Standing in one place too long
  • Breathing too fast (hyperventilation)
  • Severe dehydration
  • Severe pain
  • Heat exposure

Other types of fainting
Heart problems are another, less common cause of fainting. A temporary drop in blood flow to your brain can occur if your heart's electrical system malfunctions, which can cause your heart rate to be very slow (bradycardia) or very fast (tachycardia). A temporary drop in blood flow to your brain also can occur if there's an obstruction of blood flow from your heart, as can be caused by a thickening of the aortic valve (aortic stenosis), or if you have a heart attack.

Fainting can also occur due to neurological problems, such as brain tumors or bleeding into the brain. In addition, there are many other conditions that can lead to fainting, such as severe blood loss. Fainting that occurs due to one of these causes is no longer considered to be vasovagal syncope.

In some cases, the cause of fainting can't be determined, and it sometimes can be difficult to distinguish fainting from other causes of altered consciousness, such as epilepsy.

Risk Factor :
The following may increase your tendency to faint :

  • Certain heart conditions, such as blood flow obstructions and arrhythmias
  • Illnesses that affect your autonomic nervous system, such as Parkinson's disease
  • Anxiety or panic disorders
  • Diabetes
  • Alcohol use or drug use, or both
  • Dehydration
  • Certain prescription medications, such as some high blood pressure medicines that cause your blood pressure to drop
  • Low blood sugar

When to seek medical advice :
In many cases, fainting isn't serious — especially if you've fainted in the past under similar circumstances and no other medical cause was found.

Still, it's important to take fainting seriously. In some cases, fainting may indicate another health problem, such as a heart rhythm disorder. Visit your doctor if you experience fainting and you :

  • Have fainted more than once in a single month
  • Have heart-related problems, diabetes or high blood pressure
  • Are older than age 50
  • Had no warning signs leading up to the faint
  • Faint when you turn your head
  • Are taking a new medication
  • Experience chest pain, an irregular heartbeat, shortness of breath or blurred vision before or after fainting
  • Are pregnant
  • Injured yourself from a fall as a result of fainting
  • Take longer than a few seconds to regain consciousness

If you have slurred speech or difficulty moving an arm or leg after fainting, get immediate medical help. These signs may indicate a stroke.

Symptoms :
Before a faint due to vasovagal syncope, you may have warning signs and symptoms, such as:
  • Pale appearance to your skin
  • Feeling of warmth
  • Weakness
  • Lightheadedness
  • Nausea
  • Yawning
  • Sweating
  • Rapid breathing (hyperventilation)
  • Blurred vision
  • Field of vision "blacking out" or "whiting out"
  • Difficulty hearing or ringing in your ears

The signs and symptoms above may precede either a near faint (pre-syncope) or total loss of consciousness (syncope). But in either situation, you recover or regain consciousness on your own. Adults who faint often have a history of fainting during childhood.

Dignosis :
Your doctor will discuss with you your history of fainting and conduct a physical exam. The goal is to determine the cause of your fainting.

During the history, your doctor will ask about the details of your fainting, including :

  • What you were doing just before you fainted
  • What signs and symptoms, if any, you experienced before you fainted
  • How you felt after you fainted
  • Whether you've had other recent fainting episodes, or if this was your first

During the physical examination, your doctor will listen to your heart and lungs, and check your blood pressure.

In some cases, your doctor will be able to determine the cause of your fainting episode based on the history and physical exam. However, if the reason is still unclear or your doctor needs to verify a diagnosis, he or she may recommend one or more of the following tests to help determine if a heart-related problem is causing or contributing to your fainting :

  • Chest X-ray. In this test, radiation passes through your body to produce an image on a piece of film or a digital plate.
  • Electrocardiogram (ECG). This test records the electrical signals produced by your heart.
  • Echocardiogram. This test uses ultrasound imaging to view the heart and look for conditions, such as valve problems, that can cause fainting.
  • Heart rhythm monitoring. Your doctor may use different monitoring devices to diagnose rhythm problems. A Holter monitor is a portable device that you wear and which records your heart rhythms for an entire 24-hour period as you go about your regular routine. An event recorder keeps a record of heart rhythms just when the symptoms are happening.
  • Exercise stress test. This test studies heart rhythms during exercise (physical stress). It's usually conducted while you walk or jog on a treadmill.
  • Tilt table test. In this test, you are tilted on a special table while your blood pressure and heart rate are monitored. In vasovagal syncope, this test often reproduces your symptoms.

Complication :
Because fainting can lead to falls, injuries — ranging from bumps and bruises to serious blows to the head — can occur. If a serious injury occurs, contact your doctor or go to the emergency room right away.

For many people, repeated fainting episodes can be worrisome. If you're feeling anxious or depressed about frequent fainting, talk with your doctor or a mental health professional.

Treatment:
In most cases of vasovagal syncope, treatment is unnecessary. Your doctor may help you identify your fainting triggers and discuss ways you can avoid them.

Your doctor may recommend specific techniques to decrease the pooling of blood in the legs (orthostatic training). This may include foot exercises, wearing knee- or thigh-high, elastic stockings (compression stockings), or tensing your leg muscles when standing.

Occasionally, a doctor may prescribe medications called beta blockers, which may diminish the chance that triggers will cause vasovagal syncope.

If fainting is caused by another condition — such as heart or neurological problems, your doctor will suggest a specific treatment for that condition.

Prevention:
It may be possible to prevent a fainting episode — even when you're already experiencing the telltale signs and symptoms. When you feel like you're going to faint, find a safe place to lie down and if possible, lift your legs up. This allows gravity to keep blood flowing to your brain. If you can't lie down, sit down and put your head between your knees. Don't stand up until you no longer feel like you're going to faint.

Another method to prevent passing out is to stand with your legs crossed and thighs squeezed tightly together (scissors position). This position can help prevent blood from pooling in your legs.

If you're prone to fainting, these tips may help prevent further episodes :

  • Avoid your triggers for fainting. Talk to your doctor to help determine your specific triggers.
  • Drink plenty of water and don't skip meals. Dehydration and not eating can lower your blood pressure and intensify blood pressure changes due to changes in position.
  • Rise slowly from a lying or sitting position. Rising gradually will give your body time to adjust.
 
Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.
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