Carotid Artery Ultrasound Interpretation Using a Pattern Recognition Approach
Section snippets
General principles
Stroke is the third leading cause of death in the Western world, after heart disease and cancer [1]. The most common identifiable cause of stroke is thromboembolic clots from the heart. Another important identifiable cause of new stroke is atherosclerotic plaque causing stenosis of the carotid bifurcation extending into the internal carotid artery [2]. Physical examination findings, such as a neck bruit, the presence of extensive atherosclerotic disease elsewhere, or clinical symptomatology
General
The patient should be examined in the supine position with arms by the sides. The shoulders should be lowered to increase access to the neck if needed. It is often helpful to tell the patient to reach for the feet if they have a short or thick neck. The head should be turned slightly away from the side being examined. In general, the patient is not scanned with a pillow under the head. If adequate access to the neck is still difficult, a pillow under the shoulders may help hyperextend the neck.
Normal carotid ultrasound waveform pattern analysis
The brain requires oxygen and nutrients throughout systole and diastole of the cardiac cycle. Thus, the internal carotid artery has a low-resistance waveform pattern. There is a tall and sharp upstroke in systole with a moderate amount of diastolic flow. The entire waveform shows antegrade flow throughout the cardiac cycle [Fig. 1A].
In contradistinction, the muscles of the face do not require blood flow in diastole. Therefore, the flow in the external carotid artery is high-resistance flow.
Summary
A high-quality ultrasound examination can be readily achieved using the techniques and principles discussed above. Once the hemodynamics of the carotid system are understood, the arterial waveforms encountered become understandable and predictable. A pattern recognition approach to waveform analysis makes accurate interpretation more likely, with a greater chance of avoiding the various pitfalls commonly encountered.
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