Echocardiography is a noninvasive ultrasound procedure used to
evaluate the structure and function of the heart. In diagnostic
ultrasonography, a harmless, high-frequency sound wave emitted from
a transducer penetrates the heart. Sound waves are reflected back
to the transducer as a series of echoes. These echoes are amplified
and displayed on the technologist/technician's screen. The study may
include M-mode recordings, two-dimensional recordings, and a Doppler
study.
M-mode echocardiography is a linear tracing of the motion of the
heart structures over time. This allows the various cardiac structures
to be located and studied regarding their movement during a complete
cardiac cycle (a heartbeat).
Two-dimensional echocardiography angles a beam within one sector
of the heart. This procedure produces a picture of the spatial
anatomic relationships within the heart.
A recent addition has been the use of a color Doppler to
echocardiography. This test detects the pattern of the blood flow
and measures the changes in velocity of the blood flow within the
heart and great vessels. These variations in blood flow and velocity
alter the ultrasound frequency. By assigning computerized weighted
numbers to these altered frequencies, one is able to map and determine
origins of velocity change and blood turbulence. Turbulent blood or
altered velocity and direction of blood flow can then be identified
by changes in color. This is seen in a photograph. In most Doppler
ultrasound, color flow imaging, blue and red represent the direction
of a given stream of blood; the various hues from dull to bright
represent varying velocities. The most useful application of the
color flow imaging is in determining the direction and turbulence
of blood flow across regurgitant or narrowed valves. Doppler color
flow also may be helpful in assessing proper functioning of
prosthetic valves.
Echocardiography, in general, is used in the diagnosis of a
pericardial effusion, valvular heart disease (e.g. mitral valve
prolapse, stenosis, regurgitation), subaortic stenosis, myocardial
wall abnormalities (e.g. cardiomyopathy), infarction, and
aneurysm. Cardiac tumors (e.g. myxomas) are easily diagnosed with
ultrasound. Atrial and ventricular septal defects and other
congenital heart diseases are also recognized by ultrasound. Finally,
postinfarction mural thrombi are readily apparent with this testing.
Another version of this test is also possible with the advances in
electronic miniturization. Echocardiography can now be done by
inserting a small transducer into the stomach via the throat. Because
the heart is so close to the upper wall, ultrasounds taken from this
position are much clearer. This procedure is referred to as
transesophageal echocardiography or TEE.
