The external carotid artery (ECA) typically shows what type of resistance waveform?

The external carotid artery (ECA) typically shows what type of resistance waveform?

• A. Low
• B. Moderate
• C. High
• D. Pulsatile

Answer: (C)

The ECA shows a high-resistance waveform because it supplies tissues with a relatively high distal vascular resistance (faces, scalp, muscles) and has numerous muscular branches that limit continuous diastolic flow. In Doppler, this appears as a strong, sharp systolic peak with a rapid falloff and little or even reversed flow during diastole—the classic high-resistance pattern (often triphasic at peripheral arteries). In contrast, the internal carotid artery feeds the brain, which has a low-resistance downstream bed, yielding forward flow throughout diastole. So, the external carotid’s waveform is best described as high resistance.

The ECA shows a high-resistance waveform because it supplies tissues with a relatively high distal vascular resistance (faces, scalp, muscles) and has numerous muscular branches that limit continuous diastolic flow. In Doppler, this appears as a strong, sharp systolic peak with a rapid falloff and little or even reversed flow during diastole—the classic high-resistance pattern (often triphasic at peripheral arteries). In contrast, the internal carotid artery feeds the brain, which has a low-resistance downstream bed, yielding forward flow throughout diastole. So, the external carotid’s waveform is best described as high resistance.