A doctor can evaluate heart sounds by listening with a stethoscope. They can be further evaluated with an echocardiogram to see what the exact cause of the murmur is. The heart has four chambers -- two upper chambers (called atria) and two lower chambers (ventricles). The heart has valves that temporarily close to permit blood 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 are produced 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 can happen when a valve does not close tightly (such as with mitral regurgitation -- the backflow of blood through the mitral valve), or when the blood is flowing through a narrowed opening or a 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 with grade I being 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.
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