In this video, you'll learn how to recognize pathology in the carotid arteries using ultrasound, how to deal with unusual waveforms, and what to do when you think you may have missed something significant.
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In this Medmastery lesson, you will learn how to recognize pathology in the carotid arteries. The typical site for atheroma is the carotid bifurcation. It's less common for atheroma, or plaque buildup to occur in the CCA, but it's important to check the entire length the CCA in both the transverse and longitudinal planes using B-mode and document any areas of irregularity or plaque.
Alternative imaging planes should be used to distinguish between a plaque and an imaging artifact. The B-mode image provides a lot of useful information. In the normal CCA, we saw that there is a clear gap between the intima and media in the walls of the artery. Early disease in the carotid territory can be recognized by thickening of the intima layer, which causes the clear gap to disappear.
This can be visualized and documented with a high frequency probe. If the atheroma is more significant, meaning that it causes a greater than 50 percent reduction in the diameter of the lumen, then this should be apparent with the color flow and pulsed Doppler. When the diameter is reduced by 50 percent, velocities will start to increase through the narrowing and will be shown in the lighter shades of red on the color flow map.
A tight stenosis, or high velocity jet just beyond a stenosis may also cause aliasing to occur in the color flow image. The mark changes from reds to blue associated with aliasing will make tight stenosis easy to identify. The pulsed Doppler waveforms and velocity measurements should then confirm the findings from the B-mode and color flow.
For example, a raised peak systolic velocity in the CCA is rare, but may indicate a significant stenosis in the CCA. A peak systolic velocity in the narrowed area that is more than double the velocity just proximal to this site would indicate a greater than 50 percent stenosis in the CCA. If this is the case, then the narrowing should have been observed on the B-mode and color flow images.
Additionally, a very low velocity waveform in the CCA may be observed. Proximal disease would be suspected If this occurs in one archery only. But, if observed in both CCas, this may indicate a significant aortic arch disease. It is more difficult to quantify the degree of narrowing in the ECA, as this usually occurs close to the origin, so obtaining accurate velocity measurements to compare with isn't possible.
However, significantly raised peak systolic velocities together with plaque found on the B-mode image suggests a significant stenosis, and this is enough information to include in the report. In the ICA, peak systolic velocity is greater than 125 centimeters a second, and increased diastolic velocities, indicate the presence of significant disease.
It is important to walk the Doppler sampling volume through the area of stenosis to ensure that the highest velocities are detected, which may occur in a jet just distal to the stenosis. In addition, a waveform demonstrating turbulent flow may be observed in the ICA, distal to a significant stenosis.
If a stenosis hasn't been found on the B-mode and color flow images, but a turbulent waveform is detected, you must go back and confirm that a stenosis hasn't been missed. You may also come across some unusual waveforms. It is important to remember that if a waveform doesn't have the normal expected characteristics, there is an underlying reason for this.
You must report this finding and be able to suggest possible causes. For example, we have already learned that a high resistant waveform in a CCA may be observed when the ICA is occluded. It is rare, but a high resistant waveform with no flow in diastole may also be observed throughout the ICA. In this case, a more distal obstruction is suspected. This might be in the intracranial part of the ICA or above, which can't be assessed with ultrasound.