Laboratory Studies
In addition to clinical evaluation of patients with suspected popliteal artery occlusive disease, laboratory tests should be performed, including a complete blood count (CBC) and blood chemistries. If a hypercoagulable state is suspected to be the underlying cause of thrombosis, a hypercoagulability profile should be ordered as well. In addition, chest radiographs should be ordered and electrocardiography (ECG) performed. Laboratory studies are used to assess intraoperative and postoperative morbidity and mortality risk.
Angiography
Conventional angiography
Conventional angiography is the criterion standard evaluation for identifying popliteal occlusion. It also allows visualization of possible targets for distal bypass. It is invasive and uses ionizing radiation and contrast material. It is two-dimensional (2D).
Magnetic resonance angiography
Magnetic resonance angiography (MRA) is a modality that does not require conventional contrast agents and often yields good arterial images. It is more sensitive than conventional angiography in imaging distal runoff vessels. Combined with arterial duplex scanning, MRA has the potential to replace contrast arteriography in the assessment of patients with distal arterial occlusive disease. MRA images can be reformatted into three-dimensional (3D) angiographic images; however, MRA has lower spatial resolution than computed tomography (CT) angiography (CTA) does.
Computed tomography angiography
CTA has become increasingly used and has evolved into a very effective imaging modality for patients with peripheral artery disease (PAD). [12] Besides being used for treatment decision and planning of the procedure, it is very useful for identifying graft failure and related complications. CTA is similar to MRA with respect to ease of use and clinical outcomes for initial imaging of PAD.
CTA makes use of ionizing radiation, and contrast material is used. The images it yields can be reformatted into 3D angiographic images. Total diagnostic cost is lower than that of MRA. [13] CTA uses the largest volume of contrast agent of all modalities and is relatively contraindicated in patients with renal insufficiency.
Duplex Ultrasonography
Examination of the popliteal region with duplex ultrasonography (US) is helpful for establishing the diagnosis of popliteal artery aneurysm (PAA), popliteal artery entrapment syndrome, and cystic degeneration of the popliteal artery. In comparison with angiography, the main benefit of duplex US is the noninvasive nature of the study. Duplex US shows less anatomic detail than angiography does.
A study by Martinelli et al found that duplex US had good diagnostic concordance with CTA in the femoropopliteal region and suggested that it could be a reliable alternative to CTA in patients undergoing endovascular revascularization. [14]
Ankle-Brachial Index
The ankle-brachial index (ABI) is used to assess the amount of blood going to the distal leg relative to that in the brachial vessels. It is capable of identifying the presence and severity of occlusive disease.
Normally, the ABI is greater than 1.0 because ankle pressures are slightly higher than arm pressures. A correlation is found between the severity of signs and symptoms of arterial insufficiency and the ABI. Generally, the ABI is decreased to 0.4-0.8 in patients with claudication. An ABI lower than 0.4 is seen in patients with critical limb ischemia (CLI), or chronic limb-threatening ischemia [CTLI]; signaled by rest pain or tissue necrosis). (See Table 1 below.)
Table 2. Clinical Category and Ankle-Brachial Index (Open Table in a new window)
Clinical Category |
ABI |
Normal |
>0.97 (usually 1.10) |
Claudication |
0.40-0.80 |
Rest pain |
0.20-0.40 |
Tissue loss |
0.10-0.40 |
Acute ischemia |
< 0.10 |
A normal ABI does not absolutely rule out the possibility of occlusion. A falsely elevated ABI can be recorded in diabetic patients and patients with renal failure because of incompressible calcified lower leg arteries. In these patients, inspection of flow velocity waveform recording from the pedal arteries in conjunction with toe pressure measurement can be used to determine the degree of ischemia. In addition, patients with mild PAD may have normal ABIs at rest and may require provocative testing with exercise to diagnose their PAD.
Tables
Rutherford Classification |
Fontaine Classification |
|||
Grade |
Category |
Clinical |
Stage |
Clinical |
0 |
0 |
Asymptomatic |
I |
Asymptomatic |
I |
1 |
Mild claudication |
IIa |
Mild claudication |
I |
2 |
Moderate claudication |
IIb |
Moderate to severe claudication |
I |
3 |
Severe claudication |
|
Ischemic rest pain |
II |
4 |
Ischemic rest pain |
III |
Ischemic rest pain |
III |
5 |
Minor tissue loss |
IV |
Ulceration or gangrene |
III |
6 |
Major tissue loss |
|
|
Clinical Category |
ABI |
Normal |
>0.97 (usually 1.10) |
Claudication |
0.40-0.80 |
Rest pain |
0.20-0.40 |
Tissue loss |
0.10-0.40 |
Acute ischemia |
< 0.10 |
Stage |
Presentation |
Diagnostic/Therapeutic Interventions |
0 |
No signs or symptoms |
Never justified |
I |
Intermittent claudication (1 block) without physical changes |
Usually unjustified |
II |
Severe claudication (< 50% blocked), dependent rubor, decreased temperature |
Sometimes justified, not always necessary; patient may remain stable |
III |
Rest pain, atrophy, dependent cyanosis, decreased temperature |
Usually indicated, but patient may do well for long periods without revascularization |
IV |
Nonhealing ischemic ulcer or gangrene |
Indicated |
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- Overview
- Presentation
- Workup
- Treatment
- Approach Considerations
- Medical Therapy
- Preoperative and Intraoperative Considerations
- Surgical and Endovascular Therapy for Popliteal Artery Occlusion
- Surgical and Endovascular Therapy for Popliteal Artery Aneurysm
- Surgical and Endovascular Therapy for Emboli, Popliteal Entrapment Syndrome, and Cystic Adventitial Disease
- Postoperative Care
- Complications
- Long-Term Monitoring
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- Guidelines
- Tables
- References
