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What is a heart murmur?
A
heart murmur is an extra or abnormal sound produced by the heart and heard with
the stethoscope.
How
does it occur?
In
most cases the abnormal sound is the result of noisy or turbulent blood flow in
the heart. The turbulence may be caused by the shape of the heart or by
abnormalities of specific heart structures, such as the valves or the heart
walls.
Heart
murmurs can be caused by congenital abnormalities (that is, abnormalities
present at birth). Murmurs can result from heart infections when a person has
rheumatic fever from streptococcal infections, such as strep throat; however,
this occurs less often now than in the past. Some murmurs do arise from heart
muscle damage resulting from coronary artery disease or hypertension.
How
are murmurs classified?
The
classification of heart murmurs is based on their loudness, where in the heart
pumping cycle they occur, and where on the chest they are best heard. From
these characteristics the likely cause of a murmur can be predicted.
Loudness is on a scale of I (faint) to VI (loud enough
to be heard even if the stethoscope is not touching the chest).
Each
pump of the heart is a two-phase process. Systole is the name for the pumping
phase. Diastole is the name for the resting, filling phase. A murmur heard
during systole is systolic; likewise, a murmur heard during diastole is
diastolic.
Murmurs are not always significant. A murmur is called
functional or benign if no symptoms are associated with it and its sound and
location do not indicate a heart problem. Such murmurs are usually found
incidentally during a physical exam. They require no further evaluation.
The
intensity and timing of a murmur, and sometimes-associated symptoms, may suggest
that the murmur is significant. Such a murmur needs to be evaluated to
determine the underlying structural problem. Many heart abnormalities can be
corrected before the heart muscle is permanently damaged.
What are the symptoms?
The
symptoms of a significant heart murmur depend on the heart abnormality and its
severity. Possible symptoms include:
- Shortness of breath
- Lightheadedness
- Inability to
tolerate exertion
- Frequent episodes
of rapid heart rate
- Chest pain
How
is it diagnosed?
Technology has made great progress beyond the simple
stethoscope in the diagnosis of heart murmurs. For example:
An
electrocardiogram can detect any associated electrical abnormalities.
A
chest x-ray screens for an enlarged heart, signs of heart muscle failure, and
certain congenital abnormalities.
An
echocardiogram uses sound waves to create images of the heart structure. The
images may show a hole in the wall of the heart or an abnormal valve.
In
some cases cardiac catheterization may be necessary to determine the structural
problem. This technique also allows measurement of the pressures in the heart
chambers and of valve function.
How
is it treated?
Some
murmurs do not require treatment. The decision for treatment depends on several
factors:
- The symptoms
- The risk of heart
damage over time if the abnormality is not corrected
- The risk of sudden
complications, such as stroke or cardiac arrest
The
treatment for correcting a defect causing a heart murmur is open heart surgery.
What can be done to help prevent heart murmurs?
Little
is known about how to prevent heart murmurs present at birth. However, the
conditions of coronary artery disease or hypertension, which can cause heart
muscle damage, can sometimes be prevented, delayed, or minimized by healthy diet
and exercise habits, and by not smoking.
Always
get prompt treatment for strep infections to prevent rheumatic heart disease.
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