Health Library : Cardiovascular Disorders

Heart Murmurs

What is a heart murmur?

Murmurs are extra or unusual sounds made by blood circulating through the heart's chambers or valves, or through blood vessels near the heart.

What causes a heart murmur?

Heart murmurs may be caused by a number of factors or diseases, including the following:

• Defective heart valves
• Holes in the interior heart walls (atrial septal defect or ventricular septal defect)
• Congenital (present at birth) heart defects
• Fever
• Anemia (a decrease in the red blood cells)

What are the different types of murmurs?

Your child's health care provider will evaluate a murmur based on several factors. Murmurs are analyzed for pitch, loudness, and duration. They also are graded according to their intensity (on a scale of one to six, with one being very faint and six being very loud).

Types of murmurs include the following:

• Systolic murmur. A heart murmur that occurs during a heart muscle contraction. Systolic murmurs are divided into ejection murmurs (often due to blood flow through a narrowed vessel or irregular valve) and regurgitant murmurs (typically due to mitral or tricuspid regurgitation where the blood leaks back into the atria from the ventricles). 
• Diastolic murmur. A heart murmur that occurs during heart muscle relaxation between beats. Diastolic murmurs are due to a narrowing (stenosis) of the mitral or tricuspid valves, or regurgitation of the aortic or pulmonary valves.
• Continuous murmur. A heart murmur that occurs throughout the cardiac cycle.

Murmurs related to a congenital (present at birth) heart defect or other problem involving the heart structures will be heard the loudest in the area of the chest where the problem occurs. Some large defects have almost no murmur in the newborn due to normally elevated pressures in the blood vessels in the lungs. Murmurs may be inconsistent and difficult to hear in an infant who is agitated or crying. Thus, murmurs may be missed or not detected.

Do all murmurs signify heart disease?

Not all heart murmurs are symptoms of heart disease. Sometimes, a murmur may be heard in a normal child who has a fever or who is anemic; these murmurs often go away when the underlying problem is treated.

Some children have what is known as an innocent murmur. These murmurs are not related to congenital heart defects, and usually resolve by the time a child reaches adulthood. If your child's health care provider hears an innocent murmur, he or she may want to perform additional tests to ensure a heart defect is not present. A child with an innocent murmur can live a normal life and be as active as any other healthy child.

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