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Echocardiogram
What is Ultrasound:
Sound is made up of several different
frequency waves. The very high frequency range is inaudible to the
human ear and is known as ultrasound. Ultrasound was used by
the Navy during World War II to detect submarines, and is widely
used by fisherman to help find schools of fish.
In each case, an ultrasound
machine is used. With the help of a
microphone-shaped device (known as a transducer) ultrasound waves
are created and beamed through water. When the beam encounters a
boundary or interface between liquid (water) and a solid (submarine
or fish) with a different density or compactness, part of the beam
is reflected back to the transducer. The remaining waves move
through the object and reach the back boundary between solid and
water. Here, some more of the ultrasound waves are reflected back to
the transducer. In other words, the transducer transmits ultrasound
and constantly receives waves that are reflected back every time the
beam travels from one density to another. The reflected
ultrasound waves are collected and analyzed by the machine. Knowing
the amount of time it took for the beam to travel from and to the
transducer, the ultrasound machine can determine the shape, size,
density and movement of all objects that lay in the path of the
ultrasound beam. The information is presented on a monitor screen
and can also be printed on paper. That is how ships detected
submarines during World War II, fishermen identify choice fishing
spots, an obstetrician can evaluate the fetus of a pregnant woman,
and a cardiologist can examine the heart of a patient.
What is an Echocardiogram: An echocardiogram is a test
in which ultrasound is used to examine the heart. The equipment is
far superior to that used by fishermen. In addition to providing
single-dimension images, known as M-mode echo that allows accurate
measurement of the heart chambers, the echocardiogram also offers
far more sophisticated and advanced imaging. This is known as two-
dimensional (2-D) Echo and is capable of displaying a
cross-sectional "slice" of the beating heart, including the
chambers, valves and the major blood vessels that exit from the left
and right ventricle
An
echocardiogram can be obtained in a physician's office or in the
hospital. For a resting echocardiogram (in contrast to a stress echo
or TEE, discussed elsewhere) no special preparation is necessary.
Clothing from the upper body is removed and covered by a gown or
sheet to keep you comfortable and maintain the privacy of females.
The patient then lies on an examination table or a hospital bed
Sticky patches or electrodes are attached to the chest and
shoulders and connected to electrodes or wires. These help to record
the electrocardiogram (EKG or ECG) during the echocardiography test.
The EKG helps in the timing of various cardiac events (filling and
emptying of chambers). A colorless gel is then applied to the chest
and the echo transducer is placed on top of it. The echo
technologist then makes recordings from different parts of the chest
to obtain several views of the heart. You may be asked to move form
your back and to the side. Instructions may also be given for you to
breathe slowly or to hold your breath. This helps in obtaining
higher quality pictures. The images are constantly viewed on the
monitor. It is also recorded on photographic paper and on videotape.
The tape offers a permanent record of the examination and is
reviewed by the physician prior to completion of the final
report.
What is a
Doppler Examination? Doppler is a special part of the
ultrasound examination that assess blood flow (direction and
velocity). In contrast, the M-mode and 2-D Echo evaluates the size,
thickness and movement of heart structures (chambers, valves, etc.).
During the Doppler examination, the ultrasound beams will evaluate
the flow of blood as it makes it way though and out of the heart.
This information is presented visually on the monitor (as color
images or gray-scale tracings and also as a series of audible
signals with a swishing or pulsating sound)..
What
information does Echocardiography and Doppler provide?
Echocardiography is an invaluable tool in providing the doctor
with important information about the following:
- Size of the chambers of
the heart, including the dimension or volume of the cavity and the
thickness of the walls. The appearance of the walls may also help
identify certain types of heart disease that predominantly involve
the heart muscle. In patients with long standing hypertension or
high blood pressure, the test can determine the thickness and
"stiffness" of the LV walls. When the LV pump function is reduced
in patients with heart failure, the LV and RV tends to dilate or
enlarge. Echocardiography can measure the severity of this
enlargement. Serial studies performed on an annual basis can gauge
the response of treatment.
- Pumping function of the
heart can be assessed by echocardiography. One can tell if the
pumping power of the heart is normal or reduced to a mild or
severe degree. This measure is known as an ejection fraction
or EF. A normal EF is around 55 to 65%. Numbers below 45%
usually represent some decrease in the pumping strength of the
heart, while numbers below 30 to 35% are representative of an
important decrease.
Echocardiography
can also identify if the entire heart is pumping poorly due to a
condition known as cardiomyopathy , or if one or more isolated areas have
depressed movement (due to prior heart attacks). Thus,
echocardiography can assess the pumping ability of each chamber of
the heart and also the movement of each visualized wall. The
decreased movement, in turn, can be graded from mild to severe. In
extreme cases, an area affected by a heart attack may have no
movement (akinesia), or may even
bulge in the opposite direction (dyskinesia). The latter is seen in patients with
aneurysm of the left ventricle
or LV. It must be remembered that LV aneurysm due to an old heart
attack does not usually rupture or "burst."
-
The
top diagram on the monitor shows an ultrasound beam (gray
triangular area) traveling through the right (RV) and left (LV)
ventricle. You can also see the aorta (Ao), left atrium (LA),
aortic valve (AV) and mitral valve (MV).
- Valve Function:
Echocardiography identifies the structure, thickness and movement
of each heart valve. It can help determine if the valve is normal,
scarred from an infection or rheumatic fever, thickened, calcified
(loaded with calcium), torn, etc. It can also assess the function
of prosthetic or artificial heart valves.
The
additional use of Doppler helps to identify abnormal leakage
across heart valves and determine their severity. Doppler is also
very useful in diagnosing the presence and severity of valve
stenosis or narrowing. Remember,
unlike echocardiography, Doppler follows the direction and
velocity of blood flow rather than the movement of the valve
leaflets or components.. Thus, reversed blood direction is seen
with leakages while increased forward velocity of flow with a
characteristic pattern is noted with valve
stenosis. Echocardiography is used to diagnose
mitral valve prolapse (MVP), while Doppler identifies whether it
is associated with leakage or regurgitation of the mitral valve
(MR). The presence of MR frequently prompts the use of antibiotics
prior to any dental or non-sterile surgical procedure. Such action
helps reduce the rare complication of valve infection.
Volume
status: Low blood pressure can occur in the setting of poor
heart function but may also be seen when patient's have a reduced
volume of circulating blood (as seen with dehydration, blood loss,
use of diuretics or "water pill.", etc.). In many cases, the
diagnosis can be made on the basis of history, physical
examination and blood tests. However, confusion may be caused when
patients have a combination of problems. Echocardiography may help
clarify the confusion. The inferior vena cava (the major vein that
returns blood from the lower half of the body to the right atrium)
is distended or increased in size in patients with heart failure
and reduced in caliber when the blood volume is reduced.
- Other Uses:
Echocardiogarphy is useful in the diagnosis of fluid in the
pericardium (the sac that surrounds the heart). It also determines
when the problem is severe and potentially life-threatening. Other
diagnoses (plural for diagnosis) made by Doppler or
echocardiography include congenital heart diseases, blood clots or
tumors within the heart, active infection of the heart valves,
abnormal elevation of pressure within the lungs, etc.
How safe is
echocardiography? Echocardiography is extremely safe. There are
no known risks from the clinical use of ultrasound during this type
of testing.
How long does
it take? A brief examination in an uncomplicated case may be
done within 15 to 20 minutes. The additional use of Doppler may add
an additional 10 to 20 minutes. However, it may take up to an hour
when there are multiple problems or when there are technical
problems (for example, patients with lung disease, obesity,
restlessness, and significant shortness of breath may be more
difficult to image).
When can I expect
to receive the results? If a doctor is present during the
test or reviews it while you are still in the office, you may be
able to get the results before you leave. However, the doctor is not
routinely present during the test and you may have to wait from one
to several days before the images have been reviewed by a physician
and the results are sent to you by phone or mail. Some
physicians will discuss your case before the study is performed and
will contact you if there are significant unexpected findings. For
example, if you are expected to have a finding or known to have a
given disease, your physician may indicate that he or she will call
you only if there are significant unexpected findings. You may also
be contacted if echocardiography reveals a finding that influences a
change in treatment. For example, the presence of a distended
inferior vena cava (discussed above) may result in increasing the
dose of your diuretic or water pill, if it is indicated by other
aspects of your condition. If you are
anxious or confused about the results feel free to contact the
physician's office staff. They can usually clarify the question for
you
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