How can the normal Doppler waveforms of the ICA and ECA be compared?

The comparison of the normal Doppler waveforms of the Internal Carotid Artery (ICA) and the External Carotid Artery (ECA) is based on their hemodynamic characteristics. The ECA demonstrates higher resistance compared to the ICA due to its primary function, which supplies blood to the face and neck. This higher resistance results in lower diastolic flow because the demand for blood supply in these areas is less constant, leading to more pulsatile and intermittent flow patterns.

In contrast, the ICA typically shows lower resistance and maintains a more consistent diastolic flow, reflecting its role in supplying blood to the brain — an organ that requires a steady and continuous blood supply. Therefore, when comparing the two, the characteristic of the ECA exhibiting higher resistance and less diastolic flow accurately reflects how these vessels function under normal conditions.

Understanding these differences in Doppler waveform characteristics helps in the assessment of vascular health and the identification of potential abnormalities in carotid blood flow, which can be crucial in diagnosing conditions such as carotid artery stenosis or occlusion.