If you have a harmless heart murmur, more commonly known as an innocent heart murmur, you likely won't have any other signs or symptoms.
An abnormal heart murmur may cause no obvious other signs, aside from the unusual sound your doctor hears when listening to your heart with a stethoscope. But if you have these signs or symptoms, they may indicate a heart problem:
- Skin that appears blue, especially on your fingertips and lips
- Swelling or sudden weight gain
- Shortness of breath
- Chronic cough
- Enlarged liver
- Enlarged neck veins
- Poor appetite and failure to grow normally (in infants)
- Heavy sweating with minimal or no exertion
- Chest pain
When to see a doctor
Most heart murmurs aren't serious, but if you think you or your child has a heart murmur, make an appointment to see your family doctor. Your doctor can tell you if your heart murmur is innocent and doesn't require any further treatment or if an underlying heart problem needs to be further examined.
There are two types of heart murmurs: innocent murmurs and abnormal murmurs. A person with an innocent murmur has a normal heart. This type of heart murmur is common in newborns and children.
An abnormal heart murmur is more serious. In children, abnormal murmurs are usually caused by congenital heart disease. In adults, abnormal murmurs are most often due to acquired heart valve problems.
Innocent heart murmurs
An innocent murmur can occur when blood flows more rapidly through the heart. Conditions that may cause rapid blood flow through your heart, resulting in an innocent heart murmur, are:
- Physical activity or exercise
- Changes in your heart's structure, such as changes from heart surgery
- Not having enough healthy red blood cells to carry adequate oxygen to your body tissues (anemia)
- An excessive amount of thyroid hormone in your body (hyperthyroidism)
Changes to the heart due to aging or heart surgery may also cause an innocent heart murmur. Innocent heart murmurs may disappear over time, or they may last your entire life without ever causing further health problems.
Abnormal heart murmurs
Although most heart murmurs aren't serious, some may result from a heart problem. The most common cause of abnormal murmurs in children is when they are born with structural problems of the heart (congenital heart defect). Common congenital defects that cause heart murmurs include:
- Holes in the heart or cardiac shunts. Many heart murmurs in children are the result of holes in the walls between heart chambers, known as septal defects. These may or may not be serious, depending on the size of the hole and its location. Shunts occur when there's an abnormal blood flow between the heart chambers or blood vessels, which may lead to a heart murmur.
- Heart valve abnormalities. Congenital heart valve abnormalities are present at birth, but sometimes aren't discovered until much later in life. Examples include valves that don't allow enough blood through them (stenosis) or those that don't close properly and leak (regurgitation).
Other causes of abnormal heart murmurs include infections and conditions that damage the structures of the heart and are more common in older children or adults. For example:
- Rheumatic fever. Rheumatic fever is a serious condition that can occur when you don't receive prompt or complete treatment for a strep throat infection. Untreated rheumatic fever can permanently affect the heart valves and interfere with normal blood flow through your heart.
- Endocarditis. This is an infection and inflammation of the inner lining of your heart and valves. Endocarditis typically occurs when bacteria or other germs from another part of your body, such as your mouth, spread through your bloodstream and lodge in your heart. Left untreated, endocarditis can damage or destroy your heart valves. This condition usually occurs in people who already have heart abnormalities.
- Valve calcification. This hardening or thickening of valves, called mitral or aortic valve stenosis, can occur as you age. These valves may become narrowed (stenotic), making it harder for blood to flow through your heart, resulting in murmurs.
- Mitral valve prolapse. In this condition, the valve between your heart's left upper chamber (left atrium) and the left lower chamber (left ventricle) doesn't close properly. When the left ventricle contracts, the valve's leaflets bulge (prolapse) upward or back into the atrium, which may cause a regurgitation of blood and hence a murmur.
There aren't any risk factors for developing an innocent heart murmur.
There are risk factors that increase your chance of having an underlying condition that can cause a heart murmur from birth. These include:
- Family history of a heart defect. If blood relatives have had a heart defect, that increases the likelihood you or your child may also have a heart defect and heart murmur.
- Illnesses during pregnancy. Having some conditions during pregnancy, such as uncontrolled diabetes or a rubella infection, increases your baby's risk of developing heart defects and a heart murmur.
- Taking certain medications or illegal drugs during pregnancy. Use of certain medications, alcohol or drugs can harm a developing baby, leading to heart defects.
Factors that can increase your risk of a heart murmurs later in life include:
- Uncontrolled high blood pressure (hypertension)
- A history of rheumatic fever
- Past radiation treatment involving the chest
- A previous infection of the lining of the heart (endocarditis)
- A past heart attack
- High blood pressure in the lungs (pulmonary hypertension)
- A weakened heart muscle, which is sometimes caused by a condition known as cardiomyopathy
While there's not much you can do to prevent a heart murmur, it is reassuring to know that heart murmurs are not a disease and are often harmless. For children, many murmurs go away on their own as they grow. For adults, murmurs may disappear as the underlying condition causing them improves.