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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 ...
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 ...
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.
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 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.
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.
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 ...
The peak mitral annular velocity during early filling, e' is a measure of left ventricular diastolic function, and has been shown to be relatively independent of left ventricular filling pressure. [ 12 ] [ 13 ] [ 14 ] If there is impaired relaxation ( Diastolic dysfunction ), the e' velocity decreases.