From the SIR Residents and Fellows Section (RFS)
Teaching Topic: Position Statement on Noninvasive Imaging of Peripheral Arterial Disease by the Society of Interventional Radiology and the Canadian Interventional Radiology Association
Dhanoa D, Baerlocher MO, Benko AJ, Benenati JF, Kuo MD, Dariushnia SR, Faintuch S, Midia M, Nikolic B. Position statement on noninvasive imaging of peripheral arterial disease by the Society of Interventional Radiology and Canadian Interventional Radiology Association. J Vasc Interv Radiol. 27: 947-51.
This manuscript reviews and provides recommendations for noninvasive lower-extremity imaging of PAD. This includes both functional and anatomic tests. The functional or physiologic tests include the ankle-brachial index (ABI), segmental limb pressures, pulse volume recordings (PVRs), segmental Doppler waveforms, and oxygen testing. The anatomic tests include duplex ultrasound (US), computed tomography (CT), and magnetic resonance (MR) imaging. Because of the complexities and degree of discussion needed for each study, CT and MR imaging will be discussed in a future manuscript. Given changes to our delivery of healthcare in the United States, the manuscript serves an important role in defining the appropriate use of noninvasive imaging to improve patient selection and documenting post-procedure outcomes.
What imaging modalities constitute a complete noninvasive examination of peripheral arterial disease?
The implementation of the Affordable Care Act has brought about drastic changes to the reimbursement models for medicine. Alternative methods have emerged to enact the intended paradigm shift towards value-based and outcome-oriented delivery of healthcare instead of the standard, traditional merit-based fee-for-service model. Thus, the appropriate use of noninvasive imaging to improve pre-procedural patient selection, as well as to objectively document post-procedure outcomes, is of critical significance.
Questions to Consider
If there is a >15mmHg discrepancy between the upper extremity systolic blood pressures, hemodynamically significant disease should be considered to be present proximal to the brachial artery with the lower systolic blood pressure.
Stielger et al. proposed an ABI-Based Grading Scale as follows:
- >1.3 : Falsely high value (suspicious for medial sclerosis)
- 0.9-1.3 : Normal
- 0.75-0.9 : Mild PAD
- 0.4-0.75 : Moderate PAD
- <0.4 : Severe PAD
What are the four phases of a normal typical waveform in segmental PVR?
The four phases are:
1. A rapid systolic upstroke
2. Rapid diastolic downstroke
3. Prominent dicrotic notch (*The dicrotic notch denotes the closing of the Aortic Valve)
4. Normalization to baseline before the next cycle
How do you interpret arterial Doppler waveforms?
Normal arterial Doppler waveforms are triphasic consisting of a sharp systolic upstroke, reversal of flow below baseline and then a short forward component in late diastole. Mild PAD leads to a bisaphic waveform in which the short forward component in late diastole is lost. As PAD progresses to severe disease, the waveform continues to flatten and becomes monophasic with loss of the flow reversal. The waveform becomes rounded with a slow upstroke and slow downstroke creating the classic postobstructive tardus parvus signal.
Andrew Niekamp, MD
Diagnostic Radiology Resident, PGY-3