Free
E-newsletter
Subscribe to Housecall
Our weekly general interest
e-newsletter keeps you up to date
on a wide variety of health topics.
close window
Mayo Clinic Housecall
Stay up to date on the latest health information.
What you get
- Free weekly e-newsletter
- Mayo Clinic expertise
- Recipes, tools and other helpful information
- We do not share your e-mail address
Causes
By Mayo Clinic staffVasovagal 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.
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
References
- Syncope. The Merck Manuals: The Merck Manuals for Healthcare Professionals. http://www.merckmanuals.com/professional/cardiovascular_disorders/symptoms_of_cardiovascular_disorders/syncope.html#v1145025. Accessed Jan. 15, 2013.
- Humphries RL, et al., eds. Current Diagnosis & Treatment: Emergency Medicine. 7th ed. New York, N.Y.: The McGraw-Hill Companies; 2011. http://www.accessmedicine.com/content.aspx?aID=55749292. Accessed Jan. 14, 2013.
- Jardine DL. Vasovagal syncope: New physiologic insights. Cardiology Clinics. 2013;31:75.
- Aminoff MJ, et al. Clinical Neurology. 7th ed. New York, N.Y.: The McGraw-Hill Companies; 2009. http://www.accessmedicine.com/resourceTOC.aspx?resourceID=66. Accessed Jan. 14, 2013.
- Angaran P, et al. Syncope. Neurology Clinics. 2011;29:903.
Find Mayo Clinic on