Symptoms

Before a faint due to vasovagal syncope, you may experience some of the following:

• Skin paleness
• Lightheadedness
• Tunnel vision — your field of vision is constricted so that you see only what's in front of you
• Nausea
• Feeling of warmth
• A cold, clammy sweat

When to see a doctor
Because fainting can be a sign of a more serious condition, such as heart or brain disorders, you may want to consult your doctor after a fainting spell, especially if you never had one before.

Causes

Vasovagal syncope occurs when the part of your nervous system that regulates heart rate and blood pressure malfunctions in response to a trigger, such as the sight of blood. Your heart rate slows, and the blood vessels in your legs widen. This allows blood to pool in your legs, which lowers your blood pressure. This drop in blood pressure and slowed heart rate quickly diminish blood flow to your brain, and you faint.

Although vasovagal syncope can occur at any age, it's being recognized as an increasingly important cause of fainting in the elderly.

Common triggers for vasovagal syncope include:

• Standing for long periods of time
• Heat exposure
• The sight of blood
• Having blood drawn
• Fear of bodily injury
• Straining, such as to have a bowel movement

Preparing for your appointment

It's a good idea to prepare for your appointment to make the most of your time with your doctor.

What you can do

• Write down a detailed description of your symptoms, including any triggers that may have precipitated your faint.
• Make a list of all your medications, including vitamins and supplements.
• Write down questions to ask your doctor, including what types of tests you might need and what treatments might be helpful.

What to expect from your doctor
Questions your doctor might ask you include:

• What were you doing just before you fainted?
• What signs and symptoms, if any, did you experience before you fainted?
• Have you ever fainted before?
• Have you recently started taking a new medication?
• Have you ever had a head injury?
• Has anyone in your family died suddenly from heart problems?

During the physical exam, your doctor will listen to your heart and take your blood pressure. He or she may also massage the main arteries in your neck to see if that causes you to feel faint.

Tests and diagnosis

The diagnosis of vasovagal syncope often involves ruling out other possible causes of your fainting — particularly heart-related problems. These tests may include:

• Electrocardiogram. This test records the electrical signals your heart produces. It can detect irregular heart rhythms and other cardiac problems that can cause fainting. In some cases, you may need to wear a portable monitor for at least a day or as long as a month.
• Echocardiogram. This test uses ultrasound imaging to view the heart and look for conditions, such as valve problems, that can cause fainting.
• Exercise stress test. This test studies heart rhythms during exercise. It's usually conducted while you walk or jog on a treadmill.
• Blood tests. Your doctor may look for conditions, such as anemia, that can cause or contribute to fainting spells.

Tilt table test
If there appear to be no heart problems causing your fainting, your doctor may suggest you undergo a tilt table test. For a tilt table test:

• You lie flat on your back on a table.
• The table changes position, tilting you upward at various angles.
• A technician monitors your heart rhythms and blood pressure to see if the postural changes affect them.

Treatment and drugs

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. However, if you experience vasovagal syncope often enough to interfere with your quality of life, your doctor may suggest trying one or more of the following remedies.

Medications
Drugs that might help prevent vasovagal syncope include:

• Blood pressure drugs. Beta blockers such as metoprolol (Lopressor) are designed to treat high blood pressure. They are also the type of drug used most often to prevent vasovagal syncope because they block some of the signals that can lead to fainting.
• Antidepressants. Selective serotonin reuptake inhibitors, such as paroxetine (Paxil), fluoxetine (Prozac) and sertraline (Zoloft), also have been successful in preventing vasovagal syncope.
• Blood vessel constrictors. Drugs to treat low blood pressure or asthma are sometimes helpful in preventing vasovagal syncope.

Therapies
Your doctor may recommend specific techniques to decrease the pooling of blood in your legs. These may include foot exercises, wearing elastic stockings or tensing your leg muscles when standing and increasing salt in your diet if you don't have high blood pressure. Avoid prolonged standing — especially in hot, crowded places — and drink plenty of fluids.

Surgery
The insertion of an electrical pacemaker, which helps regulate the heartbeat, helps some people with vasovagal syncope.

Prevention

If you feel like you might faint, lie down and lift your legs. 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 until you feel better.