The "murmur" is the sound of blood flowing. It may be passing through a heart valve that has problems, for instance. Or it may be that a condition is making your heart beat faster, forcing your heart to handle more blood quicker than normal. Heart murmurs are the result.
Common conditions can make your heart beat faster and lead to heart murmurs. It can happen if you're pregnant or if you have:
It could also be a problem with a heart valve. The valves close and open to let blood flow through the heart's two upper chambers (the atria) and two lower chambers (the ventricles). Valve problems include:
Mitral valve prolapse: Normally, your mitral valve closes completely when the lower left chamber of your heart contracts. It stops blood from flowing back into the upper left chamber. If part of that valve balloons out so that it doesn't close properly, you have mitral valve prolapse. This causes a clicking sound as your heart beats. It's fairly common and it's often not serious. But it can lead to the blood flowing backward through the valve, also called regurgitation.
Mitral valve or aortic stenosis: Your mitral or aortic valves are on the left side of your heart. If they narrow, which doctors call stenosis, your heart must work harder to pump blood out to the rest of your body. If untreated, it can wear out your heart and can lead to heart failure. You might be born with this condition. It can also happen as part of aging, or as a result of scarring from infections, such as rheumatic fever.
Aortic sclerosis and stenosis: One in three elderly people have a heart murmur due to the scarring, thickening, or stiffening (which doctors call sclerosis) of the aortic valve, although it hasn't narrowed. It's usually not dangerous, since the valve can work for years after the murmur starts. Aortic sclerosis is usually seen in people who have heart disease. But over time, the valve can narrow, also called stenosis. This can lead to chest pain, shortness of breath, or passing out. In some cases, the valve may need to be replaced.