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32 Chapter 2: Cardiovascular system
imaged. It requires technical expertise to obtain images Two dimensional is useful for evaluating the anatomical
and clinical expertise to interpret the results appropri- features. Standard views are obtained.
ately. The following features are typically assessed: Left parasternal: With the transducer rotated appro-
Anatomical features such as cardiac chamber size, my- priately through a window in the third or fourth inter-
ocardial wall thickness and valve structure or lesions. costalspace,longandshortaxisviewscanbeobtained.
Ventricular aneurysms or defects such as atrial or ven- Apical: This is a view upwards from the position of
tricular septal defects can be seen. the apex beat and gives a long axis view of the heart,
Functional features including wall motion (any lo- where all four chambers can be seen simultaneously.
calised wall motion abnormality as well as a general M-mode is a way by which the motion of individual
assessment of the overall contractility of the ventri- structures along a narrow path can be carefully studied.
cles, often measured as fractional shortening or ejec- It is a one-dimensional view (depth) with time as the
tion fraction) and valve motion. Doppler ultrasound second dimension on the image produced. Structures
is used to measure the velocity of jets of blood, e.g. to that do not move appear as a horizontal line, whereas
assess severity in valve stenosis. structures that move, e.g. valves, are seen as zigzag lines,
The aortic root may be examined for dilatation or which move in time with the cardiac cycle. The distances
dissection. between structures, or the thickness of structures, can
Pericardialfluidappearsasanecho-freespacebetween therefore be carefully measured at different times of the
the myocardium and the parietal pericardium. cardiac cycle.
Mass lesions such as thrombus or tumour may be seen Doppler allows the analysis of the direction and velocity
within the heart. of blood flow, and therefore is particularly useful in the
The principles of echocardiography are the same as evaluation of valve lesions. It is used to calculate pressure
those of ultrasound. A transducer is used to generate gradients, e.g. in aortic stenosis. It can also be used to
ultrasound waves that are directed at the heart. When generate 2-D images with simultaneous imaging of flow
awaveencounters an interface of differing echogenic- direction and velocity.
ity, some of it is reflected and some absorbed. Any Common indications for echocardiography:
reflected waves (echoes) that reach the transducer are Suspected valvular heart disease, including infective
sensed and processed into an image. The time taken endocarditis.
for the wave to bounce back measures the distance of Heart failure, to assess left ventricular function and
the interface. Tissues or interfaces that reflect the waves look for any valve lesions or regurgitation, and any
strongly such as bone/tissue or air/tissue will appear evidence of a cardiomyopathy.
very white (echogenic) and also prevent any tissues un- Postmyocardial infarction for suspected complica-
derneath from being imaged well. Fluid is anechoic, so tions, such as ventricular septal rupture or papillary
appearsblack.Theribsandlungslimittheabilitytovisu- muscle rupture. It will also identify areas of ischaemic
alise the heart because they cast acoustic shadows. Tran- myocardium or previous myocardial infarction as ar-
soesophagealechocardiography(TOE)isamoreinvasive eas of hypokinetic or akinetic myocardium, as well as
method used when poor views are obtained on transtho- an overall assessment of left ventricular function.
racic echocardiography, or when more detailed views are
required particularly of structures near the oesophagus
such as the atria and great vessels, the mitral valve or Ischaemic heart disease
prosthetic valves. A transducer probe is mounted on the
tip of a flexible tube that is passed into the oesophagus.
The patient needs to be nil by mouth prior to the proce- Ischaemic heart disease
dure, local anaesthetic spray is used on the pharynx, and
intravenous sedation may be required for the procedure Definition
to be tolerated. In the normal heart there is a balance between the oxy-
There are three types of echocardiography: two di- gen supply and demand of the myocardium. A supply of
mensional, M-mode and Doppler. oxygen insufficient for the myocardial demand results