Fainting: Uncertain Cause

Fainting (syncope) is a temporary loss of consciousness. It's often associated with a loss of postural tone. It’s also called passing out. It occurs when blood flow to the brain is less than normal. There are other causes of fainting, too. Near-fainting (near-syncope) is very similar to fainting, but you don’t fully pass out.

In most cases, fainting occurs for reasons that aren't necessarily serious or life-threatening. But it may still be dangerous if you fall or if it occurs while driving. Common triggers of less serious types of fainting include:

• Sudden fear

• Pain

• Nausea

• Emotional stress

• Overexertion

Suddenly standing up after sitting or lying for a long time can also cause fainting.

More serious causes of fainting include:

• Very slow or very fast heartbeat (arrhythmia)

• Other types of heart disease, such as heart valve disease or coronary artery disease

• Dehydration

• Loss of blood

• Stroke

• Ruptured blood vessel in the brain

Taking too much high blood pressure medicine can also cause low blood pressure and fainting.

Your healthcare provider may be able to tell why you are fainting by reviewing your health history and hearing about your fainting episodes. If the cause of your fainting remains unknown or if your healthcare provider is concerned about a more serious cause he or she may determine that you need further testing. Testing may include:

• Echocardiogram. This will take ultrasound pictures of your heart to evaluate the heart's structure and function

• Stress test. This will check for abnormalities with you heart function or heart rhythm with exercise

• Tilt table test. This evaluates for changes in blood pressure or heart rate when going from a laying position to standing

• Heart monitoring. This will evaluate for heart rhythms that are too slow or too fast that may be the cause of your fainting

• Lab tests. This can check for abnormalities in electrolytes, blood counts and other things