Murmurs are blowing, whooshing, or rasping sounds produced by turbulent blood flow in or near the heart. Often, they are caused by turbulent blood flow through the heart valves.
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 arteries 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 contract 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 are blowing, whooshing, or rasping sounds. They are the result of vibrations caused by turbulent blood flow patterns. This can happen when a valve does not close tightly (such as with mitral regurgitation), 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 all heart disorders do not 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.
Murmurs can be caused by:
- mitral regurgitation - chronic
- mitral regurgitation - acute
- mitral stenosis
- aortic regurgitation
- aortic stenosis
- tricuspid stenosis
- tricuspid regurgitation
- pulmonic stenosis
- pulmonic regurgitation
Murmurs in children are more likely to be caused by:
- patent ductus arteriosus (PDA)
- atrial septal defect (ASD)
- ventricular septal defect (VSD)
- coarction of the aorta
- anomalous pulmonary venous return
Children often have murmurs that are a normal part of development and do not require treatment. These innocent murmurs include:
- Still's murmur
- venous hum
- pulmonary flow murmurs
Regarding other heart sounds:
- Left ventricular hypertrophy (enlargement) may cause a split S2.
- Emotional stress can sometimes cause a temporary change in the heart sounds.
Call your health care provider if:
This finding is usually detected during examination by a health care provider.
What to expect at your health care provider's office
This finding is usually discovered by a health care provider during a physical examination. The patient 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 are present -- such as cyanosis, liver enlargement, distended neck veins, or lung sound changes (rales)?
Diagnostic testing to determine the cause of a "new" murmur or other abnormal heart sound may include:
- chest X-ray