When the heart pumps blood into the aorta, the pressure
gradient—the difference between the blood pressure inside the
heart and the blood pressure in the artery—is an important
diagnostic measurement. A direct measurement of the pressure
gradient is difficult, but an indirect determination can be made by
inferring the pressure difference from a measurement of velocity.
Blood is essentially at rest in the heart; when it leaves and
enters the aorta, it speeds up significantly and—according to
Bernoulli’s equation—the pressure must decrease. A doctor using 2.5
MHz ultrasound measures a 6000 Hz frequency shift as the ultrasound
reflects from blood ejected from the heart.
What is the speed of the blood in the aorta?
What is the difference in blood pressure between the inside of
the heart and the aorta? Assume that the patient is lying down and
that there is no difference in height as the blood moves from the
heart into the aorta.
