Contents
Introduction
Often just called an ‘echo’, echocardiography is ultrasound of the heart. It gives a reasonably accurate picture of the valves and chambers of the heart, and also gives an idea of the velocity of blood flow in certain areas (aka Doppler – thus helping you to determine if there is backflow / reduced flow in valve defects).
Echocardiogropahy is very widely used, and is performed in almost all patients with any suspected cardiac disease. The test is usually performed by either ultrasonographers specifically trained for echo, or by cardiologists.
As well as assessing valve (valve defects) and heart wall function (usually a marker of coronary artery disease, also useful for cariomyopathies), echo can be used to look for tamponade, vegitations in infective endocarditis (can be seen in 70% of cases)
Structures visualized
- Valves
- All 4 chambers
- Heart wall thickness
- Amount of muscle contraction
- Pericardium
- Intracardiac masses
- Ascending aorta
Types of echo
Transthoracic (TTE)
- The patient lies of their left hand side with their arm behind their head. The transducer is placed at various intercostal spaces to the left of the sternum, and at the anterior axillary line.
- This is the preferred test for valve defects
- It is also often the first line investigation when echo is required. If sufficient images are not obtained, then other methods may be attempted
Transoesophageal (TOE)
(TOE –Trans-Oesophageal Echocardiogram)
- Usually performed under sedation (e.g. with midazolam), and with facilities for resuscitation
- It provides high resolution due to the probes proximity to the heart.
- Provides good views of the posterior part of the heart – i.e. the left atrium, and descending aorta.
- This is the investigation of choice for infective endocarditis, prosthetic valve management, and searching for causes of thromboembolism.
- This is an invasive procedure, and usually performed by a cardiologist
Stress echocardiogram
- You would normally do this is conjunction with a normal transthoracic echo and compare images. You can either stress the heart with exercise, or you can give an infusion of dobutamine.
- It is used to evaluate CHD, however, you should bear in mind that the Gold Standard test for assesment of coronary artery disease is angiography.
- The presence of reversible systolic regional wall motion abnormalities are characteristic of CHD. Where angiogram might give you an indication of the level of obstruction of the coronary vessels, echo can give an indication of the existing heart damage (either due to ischaema or infarct).
- Stress echo is an alternative to ETT (exercise tolerance testing) – and is typically more sensitive and specific, although typically less sensitive than CT coronary angiogram
Uses of echo
- Find valve dysfunction
- Asses prosthetic valve function
- Assessment of left ventricular function – can be used to estimate left ventricular ejection fraction
- Atrial fibrillation
- Congenital heart disease
- Cardiomyopathy
- IE
- After embolic stroke – to try and find a possible cause; e.g. patent foramen ovale.
- Pericardial disease
Results
Ejection Fraction
- Normal value 55-70%
- 40-55% is often clinically insignificant
- <40% indicates clinically significant dysfunction
Valvular Function
- Each valve is independently assessed, and noted whether there is any regurgitation or stenosis. If present, these are usually given a rating of mild, moderate or severe
Myocardial Function
- Areas of hypokinesia (reduced movement) are noted. This indicated ischaemic muscle tissue
- Akinesic areas also noted (no movement). This indicates infarcted tissue
- Dyskinesic areas also noted (floppy areas of heart wall tissue that bulge outwards). This indicates infarcted tissue
- Heart wall thickening
- Useful as a screening tool for Hypertrophic Cardiomyopathy, where signs include assymetrical hypertrophy of the septum and LV outflow tract obstruction.
Other stuff
Some specific features are not always visualized, and if you want to assess these areas, when requesting en echo, you may need to specifically ask for them. Right ventricular function
- Diastolic function. In heart failure patients with normal systolic function, diastolic dysfunction should be assessed
- Cardiac causes of stroke
- Right ventricle