Diagnostic ultrasound ( PDFDrive )

936 PART III Small Parts, Carotid Artery, and Peripheral Vessel Sonography
A
B
C
FIG. 26.27 Abnormal Doppler Waveforms Caused by Heart
Disease. (A) Patient with aortic valvular disease and atrial ibrillation
shows irregular pulsed Doppler rhythm with varying velocities and
a delayed upstroke consistent with aortic stenosis. (B) Pulsed Doppler
waveforms in a patient with an 80% to 99% ICA stenosis and
combined aortic stenosis/insuficiency show a striking disparity in
peak systolic and end diastolic velocities due to severe aortic insuficiency.
(C) Doppler waveform from CCA in patient with aortic valve
insuficiency. Note reversal of low in diastole.
Pitfalls and Adjustments
Although absolute velocity determinations are valuable in assessing
the degree of vascular stenosis, these measurements are less
reliable in certain patients. 1 Variations in cardiovascular physiology
may afect carotid velocity measurements. 143,144 For example,
velocities produced by a stenosis in a hypertensive patient may
be higher than those in a normotensive individual with comparable
narrowing, especially in the setting of a wide-pulsed
pressure. 145 On the other hand, a reduction in cardiac output
will diminish both systolic and diastolic velocities (Fig. 26.26).
Cardiac arrhythmias, aortic valvular lesions, and severe
cardiomyopathies can cause signiicant aberrations in the shape
of carotid low waveforms and alter systolic and diastolic velocity
readings 146 (Fig. 26.27). Use of an aortic balloon pump can also
distort the Doppler velocity spectrum 147 (Fig. 26.28). hese
alterations can invalidate the use of standard Doppler parameters
to quantify stenoses. Bradycardia, for example, produces increased
stroke volume, causing systolic velocities to increase, whereas
prolonged diastolic runof causes spuriously decreased end
diastolic values resulting in underestimation of carotid stenosis. 148
FIG. 26.28 Abnormal Doppler Waveform Caused by Aortic Balloon
Pump. ICA pulsed Doppler trace shows the effect of an aortic balloon
pump on carotid waveforms. Inlation of the device in systole (arrow)
produces a second systolic peak, whereas delation produces low reversal
(arrowhead) in end diastole.