There are four valves located in the heart. Each valve consists of either two or three folds of thin tissue. When closed, the valve prevents blood from flowing backwards to its previous location. When open the valve allows blood to flow freely. Valve problems can occur because of inborn (congenital) abnormalities, rheumatic fever, infection, or other causes.
Reviewed By: Michael A. Chen, MD, PhD, Associate Professor of Medicine, Division of Cardiology, Harborview Medical Center, University of Washington Medical School, Seattle, WA. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.
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