Echocardiography is a non-invasive technique for imaging the heart.
Essentially it is a very sophisticated development of the same technology as sonar used for years in submarines and fishing boats. The basic principal is to direct a beam of very high frequency sound waves at the subject and each structure that the beam encounters reflects some of these waves back. The probe (transducer) collects these reflected sound waves and these are analysed principally in terms of the delay in bouncing off the structures (to give depth information) and the amount reflected (to give information about the density of the tissue reflecting the sound waves). Most women of today's generation are very familiar with this type of technology through having their babies scanned in the womb.
Cardiac ultrasound (Echocardiography) has developed enormously over the past 25 years and is now a very sophisticated technique. At its best it gives information not only as to the structure but also the function of the heart. It can be used to identify problems with the heart muscle (cardiomyopathies and scar tissue from heart attacks), valvular heart problems, problems involving the sac that contains the heart (pericadium) and developmental abnormalities of the heart (congenital heart disease).
Most scans are conducted by pressing the probe up against the chest wall. This is called Transthoracic Echocardiography (TTE). To improve the transmission of the ultrasound waves through the chest wall a water soluble gel is applied to the skin. Usually scans are taken from a number of different positions on the chest wall and the best positions are just to the left of the breast bone (sternum) and under the left breast. Unfortunately the ultrasound waves do not penetrate bone well so the probe has to positioned to get 'windows' of access between the ribs. Furthermore the ultrasound waves scatter in air and therefore people with certain lung diseases where there is a lot of lung tissue around the heart may not be good subjects. It may also be difficult to obtain adequate images in overweight patients.
In all people certain areas of the heart are very difficult to see as they are either too deep in the chest or 'sit' in the wrong plane to reflect the ultrasound waves. For certain structures, therefore, we need to approach the heart from a different position and here it can be very useful to conduct a study from the back of the heart. To achieve this we use a special probe called a Transoesophageal probe which is inserted into the gullet in a similar fashion as when someone is having a gastroscopy. This is called Transoesophageal Echocardiography (TOE). The oesophagus (the muscular tube connecting the back of the throat to the stomach) runs directly behind the left atrium of the heart and therefore this technique is particularly good for looking at structures in the left atrium, the mitral valve and the wall between the two atria. This procedure is often carried out with the patient lightly sedated.
Unfortunately the coronary arteies are too small for us to get any meaningful information about coronary artery disease and therefore if we need to find out if there is significant coronary artery disease the we need to use other methods. Coronary Heart Disease