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The mean velocity in the aorta varies over the cardiac cycle. During systole the mean velocity rises to a peak, then it falls during diastole. This pattern is repeated with each squeezing pulse of the heart. The highest velocities are found at the exit of the valve during systole.
One parameter to quantify this difference is the pulsatility index (PI), which is equal to the difference between the peak systolic velocity and the minimum diastolic velocity divided by the mean velocity during the cardiac cycle. This value decreases with distance from the heart. [20]
In ultrasound it is usually measured from the velocity gradient SR = (v 2 - v 1)/L where v 2 and v 1 are the myocardial velocities at two different points, and L is the instantaneous distance between them. This is thus equivalent to the velocity difference per length unit (the spatial derivative of velocity) and has the unit s −1. Strain is ...
The slope of ESPVR (Ees) represents the end-systolic elastance, which provides an index of myocardial contractility. The ESPVR is relatively insensitive to changes in preload, afterload, and heart rate. This makes it an improved index of systolic function over other hemodynamic parameters like ejection fraction, cardiac output, and stroke volume.
Single spectral tissue velocity curve from the mitral annulus. The curve shows velocities towards the probe (positive velocity) in systole, and away from the probe (negative velocities) in diastole. The most useful measures are the peak velocities, in systole S' and in early diastole (e') and late diastole during atrial contraction (a').
The E/A ratio is the ratio of the early (E) to late (A) ventricular filling velocities. In a healthy heart, the E velocity is greater than the A velocity. In certain conditions, especially ventricular hypertrophy, and with aging, the left ventricular wall can become stiff, increasing the back pressure as it fills, which slows the early (E ...
Decreased aqueduct stroke volume and peak systolic velocity could be detected through CSF flow to diagnose a patient with aqueduct stenosis. Normal pressure hydrocephalus (NPH) looks at CSF flow values and velocities, which is important for diagnosis because NPH is idiopathic and has varying symptoms amongst patients including urinary ...
u: is the longitudinal flow velocity, : r: is the radial coordinate, : t: is time, : α: is the dimensionless Womersley number, : ω: is the angular frequency of the first harmonic of a Fourier series of an oscillatory pressure gradient,