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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.
Typically, blood flow velocities in the common carotid artery are measured as peak systolic velocity (PSV) and end diastolic velocity (EDV). In a study of normative men aged 20-29 years, the average PSV was 115 cm/sec and EDV was 32 cm/sec. In men 80 years and older, the average PSV was 88 cm/sec and EDV was 17 cm/sec. [7]
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]
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]
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.
The physical examination usually shows weakened femoral pulses and a reduced ankle-brachial index. The diagnosis can be verified by color duplex scanning, which reveals either a peak systolic velocity ratio ≥2.5 at the site of stenosis and/or a monophasic waveform.
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 ...
Typically, blood flow velocities in the external carotid artery are measured as peak systolic velocity (PSV) and end diastolic velocity (EDV). [ 4 ] PSV values greater than 200 cm/s are considered to be predictive of more than 50% of external carotid artery stenosis .