heart and blood vessel disorders
Fainting
Key Points
Fainting usually results from insufficient blood flow to the brain. Most causes of fainting are not serious. Some less common causes are serious or potentially fatal. If fainting has an apparent trigger (such as strong emotion), is preceded by symptoms (such as light-headedness, nausea, or sweating), and requires a few minutes to recover, it is probably vasovagal syncope and is not serious. Fainting due to heart rhythm disturbances typically occurs abruptly and with a quick recovery. Doctors may ask a person who has fainted to restrict driving and operating machinery until the cause of fainting is determined and treated because if the cause is an unrecognized heart disorder, the next manifestation may be fatal. If fainting is caused by a slow heart rate, a pacemaker may be needed. 