Heart valve disease occurs if one or more of your heart valves don't work well. The heart has four valves: the tricuspid, pulmonary, mitral,and aortic valves.
                
These valves have tissue flaps that open and close with each heartbeat. The flaps make sure blood flows in the right direction through your heart's four chambers and to the rest of your body.
                
Healthy Heart Cross-Section
                

                
Birth defects, age-related changes, infections, or other conditions can cause one or more of your heart valves to not open fully or to let blood leak back into the heart chambers. This can make your heart work harder and affect its ability to pump blood.
                
Overview
                
How the Heart Valves Work
                
At the start of each heartbeat, blood returning from the body and lungs fills the atria (the heart's two upper chambers). The mitral and tricuspid valves are located at the bottom of these chambers. As the blood builds up in the atria, these valves open to allow blood to flow into the ventricles (the heart's two lower chambers).
                
After a brief delay, as the ventricles begin to contract, the mitral and tricuspid valves shut tightly. This prevents blood from flowing back into the atria.
                
As the ventricles contract, they pump blood through the pulmonary and aortic valves. The pulmonary valve opens to allow blood to flow from the right ventricle into the pulmonary artery. This artery carries blood to the lungs to get oxygen.
                
At the same time, the aortic valve opens to allow blood to flow from the left ventricle into the aorta. The aorta carries oxygen-rich blood to the body. As the ventricles relax, the pulmonary and aortic valves shut tightly. This prevents blood from flowing back into the ventricles.
                
For more information about how the heart pumps blood and detailed animations, go to the Health Topics How the Heart Works article.
                
Heart Valve Problems
                
Heart valves can have three basic kinds of problems: regurgitation, stenosis, and atresia.
                
Regurgitation, or backflow, occurs if a valve doesn't close tightly. Blood leaks back into the chambers rather than flowing forward through the heart or into an artery.
                
In the United States, backflow most often is due to prolapse. "Prolapse" is when the flaps of the valve flop or bulge back into an upper heart chamber during a heartbeat. Prolapse mainly affects the mitral valve.
                
Stenosis occurs if the flaps of a valve thicken, stiffen, or fuse together. This prevents the heart valve from fully opening. As a result, not enough blood flows through the valve. Some valves can have both stenosis and backflow problems.
                
Atresia occurs if a heart valve lacks an opening for blood to pass through.
                
Some people are born with heart valve disease, while others acquire it later in life. Heart valve disease that develops before birth is called congenitalheart valve disease. Congenital heart valve disease can occur alone or with other congenital heart defects.
                
Congenital heart valve disease often involves pulmonary or aortic valves that don't form properly. These valves may not have enough tissue flaps, they may be the wrong size or shape, or they may lack an opening through which blood can flow properly.
                
Acquired heart valve disease usually involves aortic or mitral valves. Although the valves are normal at first, problems develop over time.
                
Both congenital and acquired heart valve disease can cause stenosis or backflow.
                
Outlook
                
Many people have heart valve defects or disease but don't have symptoms. For some people, the condition mostly stays the same throughout their lives and doesn't cause any problems.
                
For other people, heart valve disease slowly worsens until symptoms develop. If not treated, advanced heart valve disease can cause heart failure, stroke, blood clots, or death due to sudden cardiac arrest (SCA).
                
Currently, no medicines can cure heart valve disease. However, lifestyle changes and medicines can relieve many of its symptoms and complications. 
                
These treatments also can lower your risk of developing a life-threatening condition, such as stroke or SCA. Eventually, you may need to have your faulty heart valve repaired or replaced.
                
Some types of congenital heart valve disease are so severe that the valve is repaired or replaced during infancy, childhood, or even before birth. Other types may not cause problems until middle-age or older, if at all.