Updated 22 May 2015

Heart murmurs

Heart murmurs are abnormal heart sounds.


What are heart murmurs?

Heart murmurs are abnormal heart sounds. They are quite common and often are harmless, but they may be caused by irregular blood flow through defective heart valves.

  • Heart murmurs can occur in healthy children, who may outgrow them as adults, or during pregnancy.
  • Heart murmurs can be a symptom of a defective heart valve or a congenital heart defect.
  • Treatment depends on the cause.

A physician can hear the normal “lub-dub” double beat of the heart through a stethoscope. He can also hear if the precise two-step of the “lub-dub” is “blurred”, producing any of an array of abnormal heart sounds. With a heart murmur either the “lub” or “dub” can sound like the static, crackling noise of a radio not quite tuned to the correct frequency or a distorted whoozing sound.

Heart murmurs can occur in healthy children, who may outgrow them as adults, or during pregnancy. If they are not associated with a disease or heart conditions, do not require treatment and are called "innocent" heart murmurs. Even if they get louder during physical activity, there is no cause for concern.

Innocent or “natural” murmurs may also occur as a result of fever, anaemia or an overactive thyroid.

However, some heart murmurs may be a symptom of serious underlying heart problems. It may be caused by blood flowing through any of the heart’s four valves that have been made leaky or have narrowed as a result of disease or an overworked and damaged heart valve. Congenital cardiac defects (heart problems present at birth) can also cause heart murmurs. These often can be repaired with surgery.


Most people do not notice innocent heart murmurs and are unaware that they have it until it is detected during a routine physical examination.

Heart murmurs that result from a heart condition may be accompanied by other signs and symptoms, including:

  • Chest pain
  • Rapid heartbeat (palpitations or arrhythmias)
  • Bluish skin colour or fingertips (sometimes seen in babies with congenital heart defects)
  • Shortness of breath
  • Lightheadedness or fainting
  • Fatigue with exertion
  • Signs of congestive heart failure

See you doctor if you have any of these symptoms.


Heart murmurs can be a symptom of a defective heart valve or a congenital heart defect. Heart-valve defects may be present at birth or may result from rheumatic fever, heart disease, heart attacks, or infective endocarditis.

The following heart valve defects are associated with a heart murmur:

  • Valvular stenosis: a narrowing of one of the heart’s four valves.
  • Mitral valve prolapse: a condition in which the flaps of the mitral valve (between the two left heart chambers) are too large and cannot close properly. As a result, blood may leak back to the left atrium through the valve (mitral regurgitation) during contraction of the left ventricle, when it should only move forward. When the mitral valve balloons out into the atrium, it causes a clicking sound with the heartbeat. In most cases this common condition is not serious, but it may leads to infective endocarditis, a serious condition.
  • Mitral valve or aortic stenosis: The mitral and aortic valves on the left side of the heart can become narrowed by scarring from infections (rheumatic fever damages the valves of many South African children), or may be narrow at birth. The heart has to work harder, and if untreated, stenosis can lead to heart failure.
  • Aortic regurgitation, in which the aortic valve (between the left ventricle and the aorta) is allowing blood to leak back into the heart.
  • Aortic sclerosis: One in three elderly people have a heart murmur due to the scarring or stiffening of the aortic valve. The valve can still function adequately for years after the murmur is detected.

Other heart defects associated with a heart murmur include:

  • Congenital heart disease: About 5 000 South African babies are born each year with holes in their heart walls, defective heart valves or other heart defects. Many of these defects can be corrected by complicated and delicate surgery.
  • Aortic aneurysm. If left untreated, the ballooned, swollen aortic wall can rupture and lead to death.
  • An enlarged heart due to a tumour.
  • An inflamed heart, due to endocarditis, myocarditis or pericarditis.
  • Increased tempo of blood flow through the heart’s lower chambers.

Some common conditions that can also result in heart murmurs include pregnancy, anaemia, high blood pressure, an overactive thyroid and fever.

Different types of heart murmurs

A heart murmur is categorised according to its occurrence in the cardiac cycle. It can be:
These murmurs occur when the blood is vigorously pumped from the heart. Systolic murmurs may be innocent, or may indicate potential problems such as aortic stenosis or mitral regurgitation.
These murmurs occur during the heart’s resting phase. All of these murmurs must be regarded as serious and may indicate aortic regurgitation or mitral stenosis.

Continuous murmurs occur through both the contraction (systolic) and resting (diastolic) cycles. They may be innocent or they may indicate the presence of heart problems. They should be investigated further.

A heart murmur can also be classified according its loudness, with grade 1 soft and grade 6 real loud.


Heart murmurs can be heard through a stethoscope and often are detected during routine physical examinations. The physician listens to the loudness, frequency, configuration and timing of the patient’s heartbeat and matches it to known and established guidelines.

If a patient has any symptoms of heart disease, or if certain murmurs indicate a more serious underlying condition, your doctor may refer you to a cardiologist (heart specialist). Children may be referred to a paediatric cardiologist for further evaluation.

Further diagnostic tests may include an electrocardiogram (ECG) to record the electrical patterns of the heart, an echocardiogram (sound waves to create a picture of the heart), a Doppler echocardiogram (an ultrasound test providing images that indicate the direction and speed of blood flow), blood tests, chest X-ray to see if the heart is enlarged, and heart catheterisation, if necessary. A heart catherisation involves measuring the pressures inside the heart, coronary angiograms, and coronary arteriograms after injection of a special dye into the coronary arteries through the catheter.


Treatment for heart murmur depends on the cause.

  • Most types of valve disease and congenital heart defects may require medication or surgery. Mitral valve prolapse requires periodic check-ups.
  • Fever (or the associated infection), high blood pressure and an overactive thyroid should be treated.
  • All people with valve disease should use preventive antibiotics before dental work or surgery to reduce the risk of heart infection.
  • Other medication may include: anti-clotting medication, medication to control irregular heartbeat, medication to control palpitations and medication to open the blood vessels.


Heart murmurs cannot be prevented except in cases where an underlying condition, such as high blood pressure, may be detected and treated before heart murmurs develop. It is imperative to prevent rheumatic fever in children and to focus on good overall heart health.


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