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 over the surface of the chest. An echocardiogram can 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 close with each heart beat, causing blood to flow in 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. Normally, there is no sound when the heart valve opens. In a person with congenital heart disease or heart valve disease, a "click" sound may be heard during a physical exam.

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

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

The health care provider can often identify the valve involved and whether you have regurgitation or stenosis during the exam. The location, quality, and timing of the murmur are all important. The doctor may ask you to squat, stand, or hold your breath while bearing down or gripping something with your hands to listen to your heart.

A murmur does not necessarily mean that you have 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. Grade I can barely be heard. An example of a murmur description is a "grade II/VI murmur." (This means the murmur is grade 2 on a scale of 1 - 6).

In addition, a murmur is described by the stage of the heartbeat when the murmur is heard. When a murmur is more prominent, the doctor may be able to feel it with the palm of the hand over the heart.

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?
• Does it change when the doctor uses physical maneuvers?
• Can the murmur be heard in other parts of the chest?

For example, a presystolic murmur is heard just before systole. It 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
• Hypertrophic cardiomyopathy (idiopathic hypertrophic subaortic 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 as a normal part of development. These murmurs do not require treatment, and may include:

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