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Heart murmurs are extra sounds that occur when blood flow through the heart or nearby blood vessels becomes turbulent. They are most often detected when a doctor listens to the heart with a stethoscope. Many heart murmurs are harmless, while others may be signs of conditions such as heart valve disease, congenital heart defects, anemia or infections. The murmur itself usually does not cause any symptoms, but the underlying condition may sometimes cause shortness of breath, reduced exercise capacity or chest pain.
Causes of heart murmurs
A heart murmur occurs when blood flow through the heart or the major blood vessels becomes turbulent, creating sounds that can be heard with a stethoscope. Heart murmurs can be completely harmless, known as physiological or functional murmurs, but they can also be caused by changes in the heart valves or other parts of the heart.
Common causes of heart murmurs include:
- Heart valve disease – narrowing or leakage of a heart valve is a common cause of heart murmurs. Examples include aortic stenosis, mitral regurgitation and aortic regurgitation.
- Congenital heart defects – congenital changes affecting the walls, valves or major blood vessels of the heart can alter blood flow and cause a heart murmur.
- Changes in the heart muscle – in conditions such as hypertrophic cardiomyopathy, the structure of the heart muscle can affect blood flow through the heart and cause a murmur.
- Increased blood flow through the heart – conditions such as anemia, fever or hyperthyroidism can increase blood flow and cause a functional heart murmur without there being a problem with the heart valves themselves. Analysis of CBC Test and Vitamin B12 can be used as part of the evaluation when anemia is suspected.
- Endocarditis – an infection of the inner lining of the heart or the heart valves can damage the valves and cause a new or altered heart murmur.
- Prosthetic heart valves – mechanical or biological valve prostheses can produce audible sounds or murmurs as a result of blood flowing through the prosthetic valve.
A heart murmur is not something you would normally hear or feel yourself. It is most often detected when a doctor listens to the heart with a stethoscope. The character of the murmur, when during the cardiac cycle it occurs and where it is heard most clearly can provide information about the possible cause.
If it is not possible to determine whether the murmur is physiological or may be caused by heart disease, further evaluation may be needed. This may include an echocardiogram, ECG or assessment by a cardiologist.
Symptoms that may occur with underlying heart disease
A heart murmur itself usually does not cause any symptoms. Any symptoms are instead related to the condition causing the murmur. Many people with heart murmurs have no symptoms at all, while more significant valve disease or other heart conditions can cause symptoms.
Depending on the underlying cause, symptoms may include:
- shortness of breath, particularly during physical activity
- reduced exercise capacity or unusual fatigue
- dizziness or fainting
- chest pain or discomfort
- palpitations
These symptoms are not specific to heart murmurs and can occur with many other conditions. A heart murmur therefore needs to be assessed together with symptoms, medical history, a clinical examination and, when necessary, further cardiac investigations.
