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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]
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').
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 ...
Applying spectral Doppler to the renal artery and selected interlobular arteries, peak systolic velocities, resistive index, and acceleration curves can be estimated (Figure 4) (e.g., peak systolic velocity of the renal artery above 180 cm/s is a predictor of renal artery stenosis of more than 60%, and a resistive index, which is a calculated ...
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 ...
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 ...
Major factors influencing cardiac output – heart rate and stroke volume, both of which are variable. [1]In cardiac physiology, cardiac output (CO), also known as heart output and often denoted by the symbols , ˙, or ˙, [2] is the volumetric flow rate of the heart's pumping output: that is, the volume of blood being pumped by a single ventricle of the heart, per unit time (usually measured ...