WCJC #7 New CPG for CLTI
Clinical Practice Guideline Document: Global Vascular Guidelines on the Management of Chronic Limb-Threatening Ischemia.
Michael S. Conte, et al.
Eur J Vasc Endovasc Surg (2019) 58, S1-S109
Much of what we do in medicine these days is based on clinical practice guidelines. This is good, and it should be evident that getting together an international group of experts in a field is likely to come up with the best evidence-based practice. When I saw this article discussing critical limb-threatening ischemia, I knew it was important. Unfortunately, some patients who are referred to my practice with lower extremity ulcerations have either been undiagnosed or undertreated for critical limb ischemia. Hopefully, these new clinical practice guidelines will help improve the prognosis and treatment of patients with peripheral arterial disease.
The authors in this article prefer the term chronic limb-threatening ischemia (CLTI) over the previously used term critical limb ischemia (CLI) because they feel that CLI implies that there is a threshold value for diagnosis versus CLTI approaches it as a continuum. They define CLTI as a clinical syndrome with the presence of peripheral arterial disease in combination with rest pain, gangrene, or limb-threatening ulceration of greater than two weeks duration. Any patient who meets these criteria should be referred urgently to a vascular specialist.
They endorse using the wound, ischemia, and foot infection (WIfI) grading system from the Society for Vascular Surgery Threatened Limb Classification System. They propose a new Global Anatomic Staging System (GLASS), which will be relevant to vascular specialists planning intervention but not of too much importance to providers referring to vascular specialists.
I am reviewing this article from the standpoint of a wound specialist who is not a vascular specialist, and the recommendations I will highlight below are what I think is new or essential for a wound specialist to know.
The first recommendation they make is to use objective hemodynamic tests to determine the presence and severity of CLTI. CLTI requires objectively documented atherosclerotic peripheral arterial disease. The parameters they cite include an ankle-brachial index (ABI) < 0.4, a toe pressure < 30 mm Hg, transcutaneous partial pressure of oxygen (TcPO2) < 30 mm Hg, and flat or minimally pulsatile pulse volume recording (PVR) waveforms. They caution relying on the ABI in patients with diabetes mellitus (DM) and end-stage renal disease (ESRD) because of the frequently falsely elevated values in medial calcinosis. For this reason, a combination of tests is preferred in patients with DM and ESRD.
Furthermore, they note that some patients may have relatively normal hemodynamics when evaluating the limb or the foot as a whole but have ulceration as a result of diminished local perfusion. This is an area where the current tools to assess regional ischemia require further development.
The second part of their first recommendation is to use a lower extremity threatened limb classification system to guide clinical management in all patients with suspected CLTI. For the wound specialist, this means referring all suspected CLTI patients to a vascular specialist to perform this classification, but I will list it here.
The WIfi classification is useful for stratifying the risk of amputation. The system has wound, ischemia, and foot infection grading. For the wound portion:
· Grade 0(W)
o No ulcer or gangrene
o Ischemic rest pain.
· Grade 1(W)
o Shallow small ulceration on the distal leg or foot without exposed bone
o No gangrene.
o If the ulceration is on the distal phalanx, there is allowed to be exposed bone.
· Grade 2(W)
o Deeper ulcer with exposed bone joint or tendon that is generally not involving the heel.
o If heel ulcer is present, it needs to be without exposed bone.
o If there is gangrene, it must be limited to the digits
· Grade W(3)
o Ulcer is extensive and deep involving the forefoot and/or midfoot.
o If involving the heel, it is full thickness with or without bone involvement.
o IF based on gangrene
§ The gangrene is extensive, involving the forefoot and/or midfoot
§ Any full-thickness necrosis of the heel.
For the ischemia grading:
· Grade 0(I)
o ABI > 0.8
o Ankle pressure (AP) > 100 mm Hg
o Toe pressure (TP) or TcP02 > 60 mm Hg.
· Grade 1(I)
o ABI 0.6-0.79
o AP 70-100 mm Hg
o TP or TcPO2 40-59 mm Hg.
· Grade 2(I)
o ABI 0.4-0.59
o AP 50-70 mm Hg
o TP or TcPO2 30-39 mm Hg.
· Grade 3(I)
o ABI <0.4
o AP < 50 mm Hg
o TP or TCPO2 < 30 mm Hg.
For the foot infection grading:
· Grade 0(fI) is uninfected.
· Grade 1(fI) is mildly infected.
· Grade 2(fI) is moderately infected.
· Grade 3 (fI) is severely infected. Mildly infected is just local infection. Moderately infected has erythema > 2cm or the presence of an abscess, osteomyelitis, septic arthritis, fasciitis, or other deep infection. Severely infected will have systemic inflammatory response syndrome with signs of local infection.
As would be imagined, the risk of amputation goes up, the higher the individual scores go up.
Skipping ahead to their recommendation #3, all patients with suspected CLTI should have a detailed history with a complete cardiovascular physical examination. A complete examination of the foot should be performed, including the assessment of neuropathy and proper bone test for any open ulcers. When explicitly discussing patients with DM and chronic kidney disease (CKD), they discuss that it is crucial to recognize incompressibility due to medial calcinosis and that it affects all values of the ABI, even those in the normal range. This should be suspected if the ABI falls in the normal range but is associated with monophasic waveforms. Toe pressure should be used when a falsely elevated ABI is detected or suspected, particularly when nonconcordant with the acoustic or visual waveform. Toe pressures < 30 mm Hg and toe brachial index (TBI) < 0.7 are associated with advanced ischemia.
If toe pressure or TBI is not available, consider using other non-invasive assessments of perfusion such as PVR, TcP02, or skin perfusion pressure. After evaluation, in patients who are still suspected of having CLTI, duplex ultrasound imaging is the test of choice. CT angiography and Magnetic Resonance Angiography (MRA) are also choices. MRA has the advantage of not exposing the patient to ionizing radiation or iodinated contrast material, and contrast-induced nephropathy is extremely rare.
Any patient with CLTI who is considered a potential candidate for revascularization should undergo an angiogram.
Recommendation #4 covers medical management. All patients with CLTI should be treated with an antiplatelet agent and statin therapy. Blood pressure should be controlled to less than 140/90. For patients with DM, hemoglobin A1c of < 7% should be considered controlled, and metformin should be the primary hypoglycemic agent for type 2 DM. Smoking cessation should be discussed every visit with smokers. Appropriate analgesics should be prescribed as needed, and opioids may be necessary for pain control.
Recommendation #9 discusses amputation. They recommend considering transmetatarsal amputation (TMA) in CLTI patients who would require more than two digital ray amputations for digital necrosis, especially if the Hallux is involved. Primary amputation should be considered in patients who have pre-existing dysfunctional or unsalvageable limb with poor functional status or a short life expectancy. All amputation decisions should be a shared decision between the patient and the healthcare team.
Secondary amputation should be considered in patients who have failed revascularization or have an ineffective reconstruction in whom no further revascularization is possible, and the patient has incapacitating pain, nonhealing wound, or uncontrolled sepsis in the affected limb.
Revascularization should be considered to increase the likelihood of healing a more distal functional amputation, particularly in patients with a high likelihood of rehabilitation and continued ambulation.
Overall, I think this is a very well done clinical practice guideline published by over 50 different authors representing many international societies. I believe anyone involved in drafting policies for a wound care center, limb salvage center, or vascular center should read it in detail. Also, vascular specialists should be well familiar with all of the recommendations in the article. Wound care specialists should be aware of all the areas that I highlighted. Reading the other recommendations may not be necessary as they are specific to vascular proceduralists. However, I do think it is helpful for wound care specialists to understand the rationale behind the decisions interventionalists make.
Two specific areas that I think would be helpful for all practitioners who see patients at risk for CLTI be aware of, not just wound specialists, has to do with ABI and ultrasound. Over the years, I have seen numerous practitioners rely upon falsely normal ABIs in patients with diabetes mellitus and ulceration. As many other published articles in the past have made clear and has been discussed in this article, a normal ABI in the presence of rest pain, tissue loss, or gangrene in a patient with diabetes mellitus cannot be excluded from having CLTI. These patients require additional non-invasive testing, which could include toe pressure, pulse volume recording, skin perfusion pressure, TcPO2, or duplex ultrasound.
Additionally, over the years, I’ve had numerous patients who had lower extremity duplex ultrasounds, where the interpretation noted the presence of monophasic waveforms but did not show any specific stenosis. Many ordering providers have incorrectly assumed that the absence of reported stenosis despite the finding of monophasic waveforms means that the test is negative and does not require further evaluation and vascular consultation. Something is causing the monophasic waveform, and patients in this situation may not heal until appropriate vascular consultation and intervention have occurred.