What can an absence of systolic window in a spectral display indicate?

An absence of a systolic window in a spectral display is typically indicative of turbulence or obstruction within the vascular system. When blood flows smoothly, particularly in healthy arteries, there is a clear systolic window, representing laminar flow with minimal disturbance. However, when there is turbulence, often caused by narrowing or blockage in the vessel, the smooth flow is disrupted.

This disruption results in a chaotic flow pattern that can obscure the typical systolic window seen in the spectral Doppler waveform. Conditions such as atherosclerosis or significant stenosis can lead to these turbulent flow patterns. In contrast, a normal arterial condition would present with a distinct systolic window, and sustained high velocity flow, while it may affect the waveform's appearance, usually still allows for a recognizable window. Additionally, while the presence of collateral flow might alter waveforms, it typically does not eliminate the systolic window entirely but could rather change its characteristics.

Thus, the absence of the systolic window is closely associated with abnormalities in the hemodynamics of the vessel, highlighting potential issues such as turbulence or obstruction.