There are many possible causes of heart murmurs.
People can categorize murmurs according to what causes them:
- Flow murmurs: Exercise, pregnancy, and anemia can all cause a high blood flow, as can hyperthyroidism, fever, and rapid growth spurts. This could lead to an innocent murmur.
- Valve disease-related murmurs: Problems with a valve in the heart, such as aortic stenosis or a bicuspid aortic valve, can lead to a heart murmur.
- Murmurs due to ventricular problems: Conditions that affect the ventricles and the flow of blood through them, such as functional mitral regurgitation, may cause a murmur.
- Murmurs due to complications of other conditions: Some conditions that affect the heart, such as endocarditis and lupus, may also cause a heart murmur.
- Murmurs related to congenital heart disease: Problems with the heart that are present from birth, such as a hole in the heart, can result in a murmur.
People with abnormal heart murmurs may have congenital heart disease or a heart valve disease.
Heart valve disease is the result of a defect in the heart’s structure. Some of these conditions can be present at birth or acquired.
Heart defects can affect the following parts of the heart:
- the aortic valve, which can be bicuspid (two leaflets) instead of tricuspid (three leaflets)
- the pulmonary valve
- the atrial septum, which separates the atria
- the ventricular septum, which separates the ventricles
Another heart defect is a patent ductus arteriosus. This occurs when the opening between the aorta and pulmonary artery does not close after birth, as it should.
When heart valve defects occur in adults, heart murmurs can be the result of age, tumors, or infections. For example, calcium can build up in the heart valves with age. This reduces the opening of the valves, making it harder for blood to pass through them.
Sometimes, the aortic valve becomes dilated or stretched and stops working properly. This causes blood to leak backward, producing a heart murmur. Doctors call this condition aortic regurgitation.
It is also possible to develop infective endocarditis. This is a bacterial infection of the lining of the heart, which can also affect the valves. The growth of bacteria will narrow the opening of the valves and affect blood flow through them.
Another condition that can affect the heart is chronic rheumatic heart disease. People with this condition have chronic inflammation in the heart valves, which affects the function of the valves and therefore the blood flow through those valves.
Tumors can also form on a heart valve. Tumors in other parts of the heart, such as the left atrium, can cause a heart murmur by affecting the blood flow through the heart.
Other conditions that can cause heart murmurs, include:
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