An invaluable tool to augment the stethoscope and clinical sense
- The use of very high-frequency sound waves to identify cardiac structures is
based on the fact that the probe used by the operator both sends and detects
high-frequency sound waves and the speed at which they are reflected back gives
the operator information of the distance the structures are from the probe
and a 2-dimensional picture can be built up.
- The echocardiogram only works as we have piezoelectrical chips that can both produce and detect high-frequency sound waves (2-10 Mhz). Sound waves bounce back "they echo" from the interfaces between adjacent media such as blood and a vessel wall or heart cavity. The piezoelectrical crystals can detect these "echoes" bouncing back and can then calculate the distance away from the crystal that the echo came from as the speed of sound remains almost constant.
- The heart is a constantly moving structure and the first echos involved just a single fixed cut through the heart showing the changing position of structures. This single-dimensional echo was called M mode and is still used to measure structures in a normal echo examination. However present echos are 2 dimensional as there is a whole array of microprocessors so a complex picture of underlying structures can be shown with respect to time.
- Echo waves travel best across a fluid medium and are hindered by lungs and bone. Transthoracic echocardiography is non-invasive but is sometimes troubled by those in whom a good window to see structures is difficult to attain due to obesity, chest disease or discomfort. Tranoesophgeal echocardiography is a far more sensitive test and allows very high-resolution inspection of the left atrium, the mitral valve and the aorta and associated structures. It is however invasive and requires some sedation.
- Doppler echocardiography uses the basic physics that blood moving towards the probe will be seen to be at a higher velocity than that moving away and this can be reflected in the display and help to show intracardiac flow and from that can be used to measure pressures across valves. It can also show the direction or absence of flow through a shunt.
- Murmur with symptoms or abnormal ECG changes or history of rheumatic fever
- Stroke in a person under 45 (also consider Transoesophageal echo)
- Stroke in a person over 45 and suspicious of the cardioembolic source
- Assessment of LV function and valves in suspected CCF
- Arrhythmias e.g. VT and assessment of LV function
- Acute assessment of LV function and regional wall anomalies in the setting of ACS
- Cardiogenic shock - suspected VSD, MR, Tamponade
- Suspected pericardial tamponade
- Suspected cardiomyopathy e.g. dilated, restrictive, HCM
- Screening for Hypertrophic cardiomyopathy
- Suspected Infective endocarditis (also consider Transoesphageal echo)
- Atrial myxoma
- Atrial fibrillation where echo will alter management
- Suspected pulmonary hypertension
- Pregnancy and suspected non-innocent murmur
- Routine valve disease follow up
- Initial assessment and follow up of congenital heart disease
- Dobutamine stress echo to look for Ischaemic heart disease