Lower Extremity Arterial Testing
Normal blood flow velocities decrease as you go from proximal to distal. These are some common normal peak systolic velocities:
- External iliac artery 119 cm/s
- Common femoral artery 114 cm/s
- Superficial femoral artery 91 cm/s
- Popliteal artery 69 cm/s
Peripheral artery stenosis is considered significant when the diameter reduction is 50% or greater, which corresponds to 75% cross sectional area reduction. The stenosis PSV to pre-stenotic PSV is 2.0 or greater.
Per University of Washington duplex criteria:
- 1-19% stenosis: Triphasic waveforms with minimal spectral broadening. Ratio is less than 1.3 (or 30% increase in PSV in the stenosis)
- 20-49% stenosis: Triphasic waveforms but significant spectral broadening. Proximal and distal waveforms are normal. Ratio is <2.0
- 50-99% stenosis: Monophasic waveforms. There is no reverse or forward flow components. Spectral broadening is present. Ratio > 2.0. Distal PSV is reduced with monophasic waveforms.
- Occlusion: No flow in the occluded segement with water hammer, pre-occlusive thump proximally. Distal waveforms are monophasic with low PSV.
Post-Angioplasty Surveillance
| Stenosis | PSV | Vr | EDV | Distal Waveform |
| <50% | <180 | <2.0 | 0 | Normal |
| >50% | 180-300 | 2.0-3.5 | >0 | Monophasic |
| >70% | >300 | >3.5 | >45 | Dampened, monophasic |
| Occlusion | - | - | - | Dampened, monophasic |
Postoperative Graft Surveillance
The velocity criteria used in bypass graft surveillance is similar to above, except that EDV is not used and mean graft velocity, which is just the average PSV of 3-4 PSV of non-stenotic segments of the graft, is used.
| Stenosis | PSV | Vratio | ABI Change | Mean Graft Flow | Category |
| >70% | >300 | >3.5 | >0.15 | <45 | I - Highest Risk, repair immediately |
| >70% | >300 | >3.5 | <0.15 | >45 | II - High Risk, repair in 2-3 weeks |
| 50-70% | 180-300 | >2.0 | <0.15 | >45 | III - Moderate Risk, repeat duplex 4-6 weeks |
| <50% | <180 | <2.0 | <0.15 | >45 | IV - Low risk, duplex in 6-12 months |
Upper Extremity Arterial Testing
Wrist-Brachial Index (WBI):
Wrist brachial index: Normal around 1.0
Normal finger to brachial index: 0.8
Digital Pressure and PPG
- Digital pressure 30 mmHg less than brachial pressure is considered abnormal.
- PPG waveforms should have the same morphology as lower extremity wavforms, with sharp upstroke and dicrotic notch.
- In obstructive disease, waveform is monophasic and dampened
- In spastic syndrome, the waveform has a rounded peak and early shift of the dicrotic notch. The amplitude is decreased but not as much as obstructive waveforms.
Cold challenge test:
- Patient’s hand is immersed in ice water for 30-60 seconds. Serial temperatures measured until finger returns to pre-test temperature, with recovery time of 10 minutes or less being normal. Rarely used and not specific to disease, with 50% false positive rate.
- Nielsen’s test involves using a finger cuff perfused by cold fluid. Serial finger pressures measured while perfusing cold fluid until pressure is reduced by 17% compared to a reference finger without cold perfusion.
Upper Extremity Duplex:
- No specific velocity criteria
- Loss of triphasic waveforms, presence of spectral broadening, and post stenotic turbulence are signs of significant stenosis.