Fainting is the sudden loss of consciousness.

Causes

In general, fainting is caused by decreased blood flow to the brain.

This can occur due to:

• Vasovagal spells (most common cause) – simple fainting that can occur:

• • During medical procedures

• • During times of high stress, trauma, or fright

• • After standing still for a long period of time

• Low blood pressure, especially when standing (called orthostatic hypotension)

• Dehydration

• Anemia due to blood loss

• Side effect of a medication

• Seizure

• Stroke or transient ischemic attack

• Too rapid or too slow heart rhythm

• Organic heart problems such as:

• • hypertrophic cardiomyopathy

• • pulmonary stenosis

• • constrictive pericarditis

Risk Factors

A risk factor is something that increases your chance of getting a disease or condition.

• Heart disease, especially congestive heart failure or abnormal rhythms

• Blood loss

• Medications, including:

• • Blood pressure medications

• • Drugs that enlarge blood vessels

• • Antidepressants

• • Drugs that regulate the heart's rhythm

• • Water pills (diuretics)

Symptoms

Symptoms include:

• Sudden loss of consciousness

• Inability to remain standing or sitting

• Consciousness regained without any need for intervention

• Dizziness or lightheadedness before losing consciousness

Diagnosis

The doctor will ask about your symptoms and medical history, and perform a physical exam.

Tests may include (in order of importance):

Blood Tests – to look for anemia, hypoglycemia, low potassium, and low magnesium

Electrocardiogram (EKG) – a test that records the heart's activity by measuring electrical currents through the heart muscle

Holter Monitoring – a mobile EKG test that is performed over 24 hours while you go about your usual daily activities

Head CT Scan – a type of x-ray that uses a computer to make pictures of the brain

MRI Scan of the Brain – a test that uses magnetic waves to make pictures of the brain

Echocardiogram – a test that uses high-frequency sound waves (ultrasound) to examine the size, shape, and motion of the heart

Cardiac Catheterization – a tube-like instrument inserted into the heart through a vein or artery (usually in the arm or leg) to detect problems with the heart and its blood supply

Electroencephalogram (EEG) – a test that records the brain's activity by measuring electrical currents through the brain

Treatment

Treatment will depend on the underlying condition that has caused fainting. For example:

• Abnormal heart rhythms can be treated with medications or by implanting a pacemaker.

• If a medication is causing syncope, it may need to be changed or discontinued.

• Anemia or other blood abnormalities should be treated.

Prevention

If you feel any warning signs, such as dizziness or lightheadedness, sit or lie down immediately so that you don't get hurt falling during a fainting spell.

In a recent randomized trial involving 223 patients with vasovagal syncopy, training to perform certain maneuvers during warning signs of an impending spell reduced the risk of recurrent symptoms. (J Am Coll Cardiol. 2006 Oct 17;48(8):1652-7. 2006 Sep 26.) These physical counterpressure maneuvers, designed to rapidly raise blood pressure and increase blood flow to the brain, included:*

• Crossing the legs while tensing the muscles of the legs, abdomen, and buttocks

• Forcefully squeezing a rubber ball or any other available object as hard as possible in the dominant hand

• Gripping one hand with the other while tensing both arms and raising the elbows slightly

If you are prone to fainting:

• Get up slowly and carefully from lying down. Start by sitting up. Don't ever jump to a standing position.

• Ask your doctor if you should be on a high-salt diet.

• Drink lots of fluids.

RESOURCES:

American Heart Association
http://www.americanheart.org

References:

Cecil Textbook of Medicine. 21st ed. W.B. Saunders Company; 2000.

Griffith's 5-Minute Clinical Consult. 2001 ed. Lippincott, Williams, and Wilkins; 2001.

Updated Treatment section on 2/6/2007 according to the following study, as cited by DynaMed's Systematic Literature Surveillance: van Dijk N, Quartieri F, Blanc JJ, et al. Effectiveness of physical counterpressure maneuvers in preventing vasovagal syncope: the Physical Counterpressure Manoeuvres Trial (PC-Trial). J Am Coll Cardiol. 2006;48(8):1652-1657.