Ultrasonic Measurements of Coronary Blood Flow

Abstract

Measurements of coronary blood flow have been made for approximately a century, but within the last few decades ultrasonic measurements of flow, based on the Doppler Principle, have been applied towards the quantitative measurement of blood flow in the coronary circulation. The Doppler Principle maintains that as sound waves are reflected from a moving object, the frequency of the reflected wave is shifted to a higher or lower sonic frequency, depending on the direction of movement of the particle. The precise frequency shift of the sound waves is proportional to the velocity of the moving object. Modern ultrasonic flowmetric techniques use the Doppler Principle to enable quantitative measurement of coronary blood flow or coronary blood flow velocity. For accurate measurements of coronary blood flow using ultrasonic flowmetry, several details must be known: (1) the angle between the flowing red cells and the sound beam axis; (2) the position of the ultrasonic flow probe with respect to the longitudinal axis of blood flow; (3) the cross-sectional area of the blood vessel or tube; and (4) the constant position of the piezoelectric crystal relative to the blood vessel. If these details are known or satisfied, accurate quantitative measurements of coronary artery inflow or coronary venous outflow may be made. This chapter summarizes ultrasonic flowmetric techniques that have been used to document regulation of coronary blood flow during physiological and pathophysiological conditions.