What are the Doppler waveform patterns seen when there is distal stenosis?

Doppler waveform patterns can change significantly in the presence of distal stenosis. Here are the typical changes you might see:

1. Monophasic Waveform: This is a common sign of distal stenosis. The blood flow is forward throughout the cardiac cycle, but there is no reverse flow component. This indicates a significant reduction in peripheral resistance due to the stenosis.

2. Reduced Peak Systolic Velocity (PSV): The PSV may be reduced distal to the stenosis. This is due to the reduced blood flow caused by the narrowing of the vessel.

3. Delayed Systolic Upslope: The systolic phase of the waveform may have a slow, rounded peak instead of a sharp one. This is another sign of reduced blood flow.

4. Prolonged Systolic Deceleration: The deceleration phase of the waveform may be prolonged, indicating that blood is taking longer to flow through the stenosis.

5. Absent or Reversed Diastolic Flow: In severe cases of distal stenosis, the diastolic flow may be absent or even reversed. This is a sign of very high resistance in the distal vessel.

Remember, these are general patterns and can vary based on the severity and location of the stenosis. Always correlate with clinical findings and consider further imaging if the Doppler findings are inconclusive.