The "murmur" is the sound of blood flowing. It may be passing through a problem heart valve, for instance. Or it may be that a condition makes your heart beat faster and forces your heart to handle more blood quicker than normal.

Most are innocent and don't require any treatment.

But there are exceptions. Murmurs can be linked to a damaged or overworked heart valve. Some people are born with valve problems. Others get them as a part of aging or from other heart problems.

Common conditions can make your heart beat faster and lead to heart murmurs. They can happen if you're pregnant, or if you have:

    Anemia
    High blood pressure
    Overactive thyroid
    Fever

A murmur 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 -- called 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 your upper left chamber. If part of that valve balloons out so it doesn't close properly, you have mitral valve prolapse. This causes a clicking sound as your heart beats. It's fairly common and often not serious. But it can lead to the blood flowing backward through the valve, which your doctor may call regurgitation.

Mitral valve or aortic stenosis:
Your mitral and aortic valves are on the left side of your heart. If they narrow, which doctors call stenosis, your heart has to work harder to pump blood to the rest of your body. If left untreated, it can wear out your heart and lead to heart failure. You might be born with this. It can also happen as part of aging, or because of scarring from infections such as rheumatic fever.

Aortic sclerosis and stenosis:
One in three elderly people have a heart murmur because of the scarring, thickening, or stiffening of their aortic valve. That’s aortic sclerosis. It's usually not dangerous, since the valve can work for years after the murmur starts. It’s usually seen in people who have heart disease. But the valve can narrow over time. This is called stenosis. It can lead to chest pain, shortness of breath, or you may pass out. Sometimes, the valve needs to be replaced.

Many children and adults have harmless heart murmurs, which don't need treatment.

If another condition, like high blood pressure, is causing yours, your doctor will treat the cause.

Some types of heart valve disease may require:

    Medicines to prevent blood clots, control irregular heartbeat or palpitations, and lower blood pressure
    Diuretics to get rid of excess salt and water from your body, making it easier for your heart to pump
    Surgery to correct heart defects you’re born with
    Surgery to correct certain types of heart valve disease

https://www.webmd.com