What is an echocardiogram? Cardiology Basics

What is an echocardiogram? Cardiology Basics

Echocardiogram is ultrasound imaging of the heart. Ultrasound is high frequency sound wave which is not audible to the human ear. The machine sends out ultrasound beams intermittently to the heart and listens for the echo. For example, if duration of a pulse of ultrasound is about 1 microsecond, the next 999 microseconds are spent for receiving echoes from the body structures. This goes on in a cyclical fashion.

Computer synthesised images are then produced from the echoes received from various parts of the heart. It is similar to the location of aeroplanes in the sky by a radar system. The ultrasound signals are sent and received by a probe or transducer placed on the chest at specific locations.

If a single narrow beam is sent, only a one dimensional image is obtained, known as M-Mode or Time-Motion mode. Modern machines use an array of ultrasound crystals to send multiple narrow beams so that a live two dimensional image can be obtained. Now there are three dimensional transducers which can produce live three dimensional images of cardiac structures.

This is an echocardiogram showing all four cardiac chambers along with mitral and tricuspid valves. Left ventricle can be seen as a more muscular and larger chamber than the right ventricle. The right and left atria are seen as chambers with much thinner walls than the ventricles.

Opening and closing of tricuspid valve on right side and mitral valve on left side have been marked here.

The interventricular septum has been marked in this view.

Here the interatrial septum has been marked.

Doppler imaging is by analysing the echoes of the ultrasound beam from moving red blood cells.

You will be familiar with the difference between the sound of a moving train when it comes towards you and when it moves away from you. The same principle is applied in Doppler echocardiography.

Signals from blood moving away from the probe is colour coded blue and that moving towards the probe is colour coded red. This colour Doppler shows downward flow of blood in the descending aorta. As the probe is kept in the upper part, in the suprasternal notch, the downward flow in the aorta is colour coded blue.