Echocardiography
Echocardiography is simply an ultrasound examination of the heart. The instrumentation and techniques for echocardiography have evolved rapidly over the last 20 years. During the examination, various different ultrasound modes or techniques are employed. 'M' mode produces a graphic tracing of the movement of a cardiac structure such as a valve leaflet over time. Two dimensional echocardiography allows real time cross sectional imaging of the heart from multiple different projections. This technique provides most of the information regarding the anatomy of the heart. Most measurements are obtained using this technique. Doppler echocardiography uses ultrasound to study the velocity, direction and character of flowing blood through the structures of the heart. Echoes returning from a moving target experience a shift in frequency that is proportional to the velocity of blood flow. The frequency shift can be analysed by the systems computer to estimate the velocity of blood flow. Colour Doppler mode superimposes Doppler information on the two dimensional images by colour coding flowing blood according to the direction and velocity of flow. Using a combination of the above techniques, information about the structure and function of the heart is obtained and any abnormalities documented. The examination is performed by a specifically trained ultrasonographer with subspecialty skills in echocardiography. A report is issued to the referring doctor by the radiologist or physician on site.
The procedure
Echocardiography is performed in a standard ultrasound room. The patient lies on the examination couch and is rolled slightly to one side or the other to improve visualization of cardiac structures. Ultrasound gel is applied to the skin surface and the probe is placed in contact with the skin. Various views are obtained from either side of the sternum, from the left lower chest and from beneath the rib cage near the midline. The procedure is recorded on videotape and on hard copy laser film. An examination takes between 30 minutes to an hour depending on the ease of obtaining good images and on the type of pathology being investigated. The technique is completely harmless and does not cause any discomfort.
