Doppler echocardiography and advanced ultrasound techniques
THE CONTEXT
Doppler echocardiography detects the speed and direction of blood flow in cardiac chambers and great vessels, helping assess valvular regurgitation and stenosis.
Display and detection of abnormal flow
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Flow information can be displayed as blood velocity plotted against time at a particular point or as a colour overlay on a two-dimensional real-time echocardiographic image.
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Valvular regurgitation produces reversed blood flow and turbulence.
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Colour-flow Doppler can demonstrate mitral regurgitation as a flame-shaped yellow/blue turbulent jet entering the left atrium.
Aortic stenosis and pressure gradients
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Doppler echocardiography detects pressure gradients across stenosed valves.
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Normal resting systolic flow velocity across the aortic valve is approximately 1 m/sec. Aortic stenosis increases velocity as blood accelerates through the narrowed orifice; peak velocity may reach 5 m/sec in severe stenosis.
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In the illustrated assessment, the Doppler beam passes through the left ventricular outflow tract and aorta into turbulent flow beyond the stenosed valve.
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The maximum blood-cell velocity is used to determine the pressure gradient. The illustrated peak velocity of approximately 4.5 m/sec indicates severe aortic stenosis, with a peak gradient of 81 mmHg.
Advanced techniques
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Advanced techniques include three-dimensional echocardiography.
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Intravascular ultrasound defines vessel wall abnormalities and guides coronary intervention.