Fainting (Syncope)

Syncope is a sudden, short loss of consciousness that usually causes the body to go limp



When you faint, you do not respond to outside stimuli and your body goes limp. You may feel faint, dizzy or light headed just before you lose consciousness. A person with those symptoms is more likely to faint if he or she is standing upright. The person usually recovers spontaneously.

There are variations in the symptoms depending on what caused the fainting:

  • If the fainting is caused by cardiovascular issues, the fainting usually begins and ends suddenly without warning. It is most often due to an arrhythmia. Other types of arrhythmias may cause fainting after or with heart palpitations.
  • Fainting after an unpleasant physical or emotional shock such as being hurt, frightened or seeing blood. This type of fainting usually affects someone who is standing. Warning signs such as nausea, feeling weak, yawning, anxiety, blurring vision or swearing usually come on first.
  • When blood pools in the legs either because a person has been standing motionless for a long time or in bed for a long time and then stands up, fainting can be triggered. This type of fainting can also occur because of severe varicose veins or certain types of drugs.
  • Seizures may cause fainting. In this case, the unconsciousness is also accompanied by jerking muscles, convulsions, an inability to control the bladder or bowels or tongue biting. A person may feel confused when he or she regains consciousness.


Causes and Risk Factors

The most common cause of fainting is a sudden loss of blood flowing to the brain. This may be a result of any or a combination of the following:

  • A reduction in the amount of blood being pumped out of the heart
  • Certain drugs such as digitalis, calcium blockers and others
  • Heart conditions such as sick sinus syndrome, ventricular tachyarrhythmias, aortic stenosis
  • Heart rates that are either too low (fewer than 30 to 35 beats per minute) or too high (more than 150 to 180 beats a minute). Fainting may occur with less extreme heart rates if there is heart disease present.
  • Irregular heart rhythms (arrhythmias) or electrical abnormalities in the pacing of the heart's beats
  • Low blood sugar
  • Lung disease
  • Malfunction of a replaced heart valve

Older persons who have a greater risk of having heart or blood vessel disease are at a greater risk of fainting.



Your doctor will do a physical examination and get your medical and family history. He or she will take into consideration:

  • Your age when the fainting began
  • Your posture (standing, sitting, etc.) at the time of the fainting
  • Other health conditions you may have
  • Drugs that may have been prescribed for you, such as drugs to prevent high blood pressure, diurectics, blood vessel-opening drugs, ones that prevent abnormal heart rhythms or affect the electrical conduction and pacing of the heart
  • Warning signs or symptoms that may occur before you faint
  • Anything that may make those symptoms go away or which will prevent fainting from happening.

He or she will pay particular attention to factors that involve the heart, blood vessels, brain and nerves. This, in turn, will help define what specific tests may be needed to confirm a diagnosis.

Some of the test that your doctor may order include:

  • A fasting blood glucose test, if low blood sugar is a possibility
  • An electrocardiogram to check for electrical abnormalities in your heart or to see if you have irregular heart rhythms (arrythmias)
  • Echocardiogram to see if you have heart disease or a problem with a mechanical heart valve
  • Electroencephalogram if a seizure disorder is suspected


If you are young and have no signs of cardiovascular disease, taking simple steps like lying down or putting your feet up may be all that is needed.

In older persons, however, the fainting may be due to a combination of factors that affect the heart's ability to maintain the flow of blood to the brain.

If the fainting is a result of a heart condition, treatment may require:

  • A pacemaker, to regulate the heart beat
  • Carotid sinus radiation
  • Avoiding hypoglycemia (better management of blood sugar)
  • Treating anemia
  • Regulating electrolytes
  • Valve repair or replacement surgery
  • Drugs to treat hypertrophic cardiomyopathy and some arrhythmias
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