What statement about the spectrum characteristic of the ECA is TRUE?

The statement that the ECA (external carotid artery) contains a prominent dicrotic notch is true because the dicrotic notch is a characteristic feature seen on the arterial waveform. This notch corresponds to a brief increase in pressure following the closure of the aortic valve, indicating a phase of diastole, and is prominent in the peripheral arterial systems, including the ECA. The waveform for the ECA typically shows a rapid upstroke during systole followed by a gradual downstroke, where the dicrotic notch becomes evident, highlighting the different phases of the cardiac cycle.

In contrast, high diastolic flow is more characteristic of the internal carotid artery, which often has a sustained flow through diastole due to its supply to the brain. Extensive post-stenotic turbulence is commonly associated with significant stenosis and is again more notable in other vessels where turbulence is more evident. The mention of a flat peak suggests a waveform with less distinct features, which is not representative of the typical dicrotic notch seen in the ECA. This understanding of the waveform properties is crucial in vascular assessments, particularly when evaluating hemodynamics within the ECA.