By Richard N. Fogoros, M.D., About.com
Created: December 01, 2003
About.com Health's Disease and Condition content is reviewed by our Medical Review Board
Figure 4 - Into the left atrium
Are your symptoms merely irritating, or could they be a sign of allergies? More >
The best way to treat a headache is to prevent it. Learn how. More >
©2009 About.com, a part of The New York Times Company.
All rights reserved.