If fast upstroke and no diastolic flow is observed in CCA, where is the disease likely located?

The observation of a fast upstroke and the absence of diastolic flow in the common carotid artery (CCA) suggests a significant degree of stenosis, particularly from a more proximal location. In vascular ultrasound, a fast upstroke typically indicates increased systolic flow velocity, which is often a response to either a narrowing or obstruction in the vessel. When there is significant stenosis, especially proximal to the monitored segment, it can lead to a rapid acceleration of blood flow during systole due to the pressure differential created by the narrowed area.

The absence of diastolic flow implies that the blood is not able to flow back during diastole, which is often seen in cases of severe stenosis. Instead, the flow remains predominantly unidirectional during the cardiac cycle, leading to diminished or absent diastolic component.

In summary, when these characteristics are present in the CCA, it indicates that the disease affecting the blood flow is most likely located distal to the CCA, where the effects of a proximal stenosis are being observed. Thus, the conditions observed are consistent with a blockage or significant narrowing that is influencing the flow dynamics downstream from the stenosis, reflecting the nature of the disease.