When pressure remains reduced for longer periods, disease at several levels is often present. The normal peripheral waveform is triphasic - Rapid forward systolic flow, then a short period of rapid reversed flow, and then a low speed forward flow in late diastole. Velocity will be lower and the waveform becomes progressively more rounded and flattened. Most severe waveform change - slow forward flow with diastolic flow to zero. Display of right and left waveforms schemetically allows easy comparison of sides and often facilitates diagnosis.
Bilateral disease does often occur however.
Below is the display of a patient with severe narrowing of the distal superficial femoral artery. In such cases, exercise or hyperemic testing may be helpful. Waveform changes simply reflect resistance changes and not ischemia. The test environment must be moderate in temperature. The patient must rest for 5-10 minutes to allow muscles to reach the resting state.