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PRINCIPLES OF ECHOCARDIOGRAPHY

• Use of ultrasound 2-5MHz waveform to assess cardiac conditions from a piezo-electric crystal which acts as a transducer (converting electrical to mechanical energy and vice-versa)

• Dynamic stress echo: chemical (dobutamine) or exercise (Bruce protocol) - gives information about myocardial viability and regional perfusion
• Resting akinesis / dyskinesis and failure of segment to thicken during systole suggests segment infarction
• Reduced wall motion during stress in a segment that otherwise contracts suggests flow limiting disease
• Improvement in function in a segment that is impaired at rest suggests stunned or hibernating myocardium
• Papillary muscle ischaemia may cause MR as a result of an inducible septal or posterior wall motion defect

Types of Echocardiography

B-mode

• Brightness mode, 2D or real-time
• 2D grayscale picture of a single plane across the heart
• Intensity of the echo is related to the brightness of the signal

M-mode

• Motion mode (more accurate than B-mode: used in measurements)
• Yields only one dimensional image of structures plotted on the y-axis

D-mode

• Doppler mode using frequency shift: reflected waves from a moving target changes frequency (toward shorter wavelenght, increased fequency) - therefore the shift is proportional to the velocity of the object
• Determines velocity and calculates gradients and valve areas
• Colour flow imaging is a colour enhanced duplex doppler echo giving blood AWAY as BLUE and TOWARD the transducer as RED - B.A.R.T

Duplex ultrasound

• Combines doppler and grayscale images to give flow and anatomical characteristics

Normal Cardiac dimensions

• Echo allows precise measurements of cardiac dimensions

Echocardiographic views

Assessment of Left ventricular function

• Quantitative methods
• Qualitative methods - scoring regional wall motion and categorising LV function as mild, moderate or severe