Which of the following indicates Doppler waveform abnormalities distal to a significant stenosis?

The presence of blunting of the peak velocity in Doppler waveforms is indicative of significant stenosis and its effects on blood flow. When there is a significant narrowing in a vessel, it disrupts the normal laminar flow and can lead to turbulence, which is reflected in the Doppler signal. Specifically, blunting occurs because the maximum velocity of blood flow is reduced due to the stenosis, and the waveform loses its characteristic sharp peak as a result. This reflects a lack of acceleration during the systolic phase of blood flow, suggesting that the flow is being impeded by the narrowed segment.

In contrast, an increased flow reversal component would typically indicate turbulence and disturbed flow, which is seen in more downstream effects rather than directly indicative of stenosis. Elongation of the peak velocity is more associated with normal variations in waveform morphology or less severe stenosis, while sharp upslopes and downslopes suggest a more normal, unobstructed flow pattern. Therefore, the characteristic of blunted peak velocity is the most direct indicator of Doppler waveform abnormalities that result from significant stenosis.