Murmurs are blowing, whooshing, or rasping sounds produced by turbulent blood flow through the heart valves or near the heart.

A doctor can check heart sounds by listening with a stethoscope. These sounds can be further tested with an echocardiogram to find the exact cause of the murmur.

The heart has four chambers -- two upper chambers (atria) and two lower chambers (ventricles). The heart has valves that temporarily close to limit blood flow to only one direction. The valves are located between the atria and ventricles, and between the ventricles and the major vessels from the heart.

Normal heart sounds are called S1 and S2. They are the "lubb-dupp" sounds that are thought of as the heartbeat. These sounds occur when the heart valves close.

Because the heart is also divided into a "right side" and a "left side," sometimes these sounds may be somewhat divided. Most commonly noted is a "split S2," caused when the right and left ventricles relax, and valves close at very slightly different times. This is normal, but occasionally the nature of the split can indicate an abnormality, such as enlargement of one of the ventricles.

Murmurs occur when a valve does not close tightly (such as with mitral regurgitation) and blood leaks backward, or when the blood flows through a narrowed or stiff valve (such as with aortic stenosis).

A murmur does not necessarily indicate a disease or disorder, and not all heart disorders cause murmurs. Murmurs are classified ("graded") depending on their ability to be heard by the examiner. The grading is on a scale in which grade I is barely detectable. An example of a murmur description is a "grade II/VI murmur." (This means the murmur is grade 2 on a scale of 1 to 6).In addition, a murmur is described by the stage of the heartbeat when the murmur is heard.

The following are important clues to the cause of the murmur:

• Does the murmur occur in the resting stage (diastole) or contracting stage (systole)?
• Does it occur early or late in the stage?
• Does it occur throughout the heartbeat?

For example, a presystolic murmur is heard just BEFORE systole and is usually caused by narrowing of the mitral or tricuspid valve (the valves between the atria and the ventricles).

The location where the health care provider hears the murmur loudest is also often noted.

Significant murmurs can be caused by:

• Aortic regurgitation
• Aortic stenosis
• Mitral regurgitation - acute
• Mitral regurgitation - chronic
• Mitral stenosis
• Pulmonary regurgitation (backflow of blood into the right ventricle, caused by failure of the pulmonary valve to close completely)
• Pulmonary stenosis
• Tricuspid regurgitation
• Tricuspid stenosis

Significant murmurs in children are more likely to be caused by:

• Anomalous pulmonary venous return (an abnormal formation of the pulmonary veins)
• Atrial septal defect (ASD)
• Coarctation of the aorta
• Patent ductus arteriosus (PDA)
• Ventricular septal defect (VSD)

Children often have murmurs that are a normal part of development and do not require treatment. These murmurs include:

• Pulmonary flow murmurs
• Still's murmur
• Venous hum

A health care provider will usually discover a heart murmur during a physical examination. You may or may not have been aware of its presence. The physical examination will include careful attention to heart sounds.

The doctor may ask the following questions:

• Have other family members had murmurs or other abnormal heart sounds?
• Is there any family history of heart problems?
• What other symptoms do you have, such as bluish skin color (cyanosis), liver enlargement, distended neck veins, lung sound changes, weight gain, swelling, or shortness of breath?

Diagnostic testing to determine the cause of a "new" murmur or other abnormal heart sound may include:

• Chest x-ray
• ECG
• Echocardiography