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Often expressed in cm/s. This value is inversely related to the total cross-sectional area of the blood vessel and also differs per cross-section, because in normal condition the blood flow has laminar characteristics. For this reason, the blood flow velocity is the fastest in the middle of the vessel and slowest at the vessel wall.
At this stage the majority of the flow can be described with velocity vectors normal to the entrance, but in plane velocities tangent to the flow are present. [3] As the path starts to curve in the ascending aorta, the blood towards the outside of the arch tends to rotate towards the inner wall, causing a helical pattern that is observed in ...
The product of average velocity and ejection time gives the stroke distance (how far the blood travels in each heart cycle). Flow time (FT) is the time difference between the sudden increase in velocity (T0) and the return to near zero velocity (T1). Stroke distance (SD) can calculated from the plug flow like velocity (v(t)):
Blood ultrasound velocity (1560–1585 m/s) is a function of total blood protein concentration—sums of proteins in plasma and in red blood red cells—and temperature. Injection of body-temperature normal saline (ultrasound velocity of saline is 1533 m/s) into a unique AV loop decreases blood ultrasound velocity, and produces dilution curves.
Blood viscosity is a measure of the resistance of blood to flow. It can also be described as the thickness and stickiness of blood. This biophysical property makes it a critical determinant of friction against the vessel walls, the rate of venous return, the work required for the heart to pump blood, and how much oxygen is transported to tissues and organs.
The E/A ratio is a marker of the function of the left ventricle of the heart. It represents the ratio of peak velocity blood flow from left ventricular relaxation in early diastole (the E wave) to peak velocity flow in late diastole caused by atrial contraction (the A wave). [1]
Velocity Time Integral is a clinical Doppler ultrasound measurement of blood flow, equivalent to the area under the velocity time curve. The product of VTI (cm/stroke) and the cross sectional area of a valve (cm2) yields a stroke volume (cm3/stroke), which can be used to calculate cardiac output.
The theory of the velocity of the transmission of the pulse through the circulation dates back to 1808 with the work of Thomas Young. [9] The relationship between pulse wave velocity (PWV) and arterial wall stiffness can be derived from Newton's second law of motion (=) applied to a small fluid element, where the force on the element equals the product of density (the mass per unit volume ...