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A heart murmur is an abnormal sound caused by turbulent blood flow. They can occur as a result of any various heart valve defects or type of congenital heart disease. The first normal sound of the heart results from the closure of the tricuspid and mitral valves at the exits from the upper chambers of the heart. The second normal heart sound is caused by the closure of the pulmonary and aortic valves at the exits from the ventricles when they have finished contracting. With a stethoscope the second heart sound is heard to consist of a double sound, especially in children and young adults. This is caused by a slight delay between the closure of the aortic and pulmonary valves. This is a normal sound. In children and young adults that is often a normal low pitched third heart sound after the second sound. But in people over the age 40, this sound is abnormal and a sign of heart failure.

If there is any abnormality of the heart muscle a fourth sound that is low pitched will often precede the first sound. An opening snap is also abnormal and may occur during the opening of the mitral valve. This is a high pitched sound that is heard shortly after the second heart sound and may be accompanied by a presystolic murmur. This is associated with mitral stenosis. An ejection sound or click is a high pitched sound caused by the abrupt halting of the valve opening. These are known to occur in hypertension or high blood pressure and in the heart valve defects such a mitral valve prolapse, aortic stenosis or pulmonary stenosis. Any abnormalities of the heart valves or heart structures can create turbulent blood flow that causes characteristics sounds that are called murmurs. Turbulent blood flows usually occur as blood moves through narrowed or leaking valves. Research has shown that not all heart disease will cause murmurs and not all murmurs indicate heart disease.

In most cases women that are pregnant will usually have heart murmurs that are caused by the normal increase in blood flow. There are also harmless heart murmurs that are common in infants and children cause by the rapid flow of blood through small structures in the heart. The vessel walls, valves and other tissues gradually will stiffen in the elderly sometimes causing turbulent blood flow even without any serious heart disease. A physician can tell by placing the stethoscope over arteries and veins elsewhere in the body and listening for sounds of turbulent blood flow. This type of blood flow is called bruits and is caused by narrowing of the vessels or abnormal connections between the vessels. Then the physician will feel the abdomen to determine if the liver is enlarged from a backup of blood in the major veins leading to the heart. He will also check the pulse and size of the abdominal aorta. If any abnormal abdominal swelling from fluid retention is present, this may indicate heart failure.