Murmurs are sounds made by blood circulating through the heart's chambers or valves, or through blood vessels near the heart.
Heart murmurs
may be caused by a number of factors or diseases, including:
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defective heart valves
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holes in the heart walls (atrial septal defect or ventricular septal defect)
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pregnancy (increased blood volume)
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fever
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anemia (a decrease in the red cells in the blood)
All murmurs are analyzed for pitch, loudness, and duration. They are also graded according to their intensity (on a scale of one to six, with one being very faint and six being very loud).
Types of heart murmurs include:
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systolic murmur - occurs during a heart muscle contraction. Systolic murmurs are divided into ejection murmurs (due to blood flow through a narrowed vessel or irregular valve) and regurgitant murmurs.
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diastolic murmur - 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.
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continuous murmur - occurs throughout the cardiac cycle.