Section: CME Category: Diabetic Foot Vascular

The Neuro-Ischemic Diabetic Foot - Recognize, Confirm, Revascularize, and Save the Limb

Robert Frykberg, DPM, MPH

Robert Frykberg, DPM, MPH discusses how to perform a complete diabetic foot exam and how to identify and treat peripheral artery disease to improve outcomes in diabetic foot disease.

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Goals and Objectives
  1. Understand how peripheral artery disease effects diabetic foot ulcer outcomes
  2. Appropriately perform a comprehensive diabetic foot exam
  3. Interpret non-invasive arterial studies and Understand how their results effect wound healing
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    Release Date: 03/16/2018 Expiration Date: 12/31/2020

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  • Lecture Transcript
  • Male speaker: Unfortunately, you have to listen to me again but I didn't wanna give up the subject of PAD. As we’ve mentioned several times today, Peripheral Arterial Disease is ever-growing problem in our diabetic patients. And our job is to detect ischemia where and when it lies. Because many of our foot ulcer patients are now complicated with this and it can be limb-threatening especially if we choose to do a major reconstruction on an ischemic limb. We know that we're going to have trouble for sure as it’s often the case. So I want to talk about the neuro-ischemic diabetic foot. This won't be a terribly long presentation but I think it's important for you to have a good appreciation for ischemia in the diabetic foot. I trained in Boston and one of my favorite papers was by Elliot Joslin, this was published in 1934. It was the "Menace of Diabetic Gangrene". And he said in that paper that diabetic gangrene has been increasing as a menace to my patients. Well it is increasing as a menace to my patients, 80 years later. So now it continues to haunt us all, and we need to understand what are the causes of diabetic gangrene. And hopefully by understanding the causes, we can help to address these problems before they necessitate completion of that causal pathway to gangrene and the necessary amputation. I'm going to show this again especially for Dr. Helfam in the back who wanted me to mention that the PAD’s increasing in our patients. It is. But the underlying problems even though they are more frequent, the underlying problems haven't changed in the last 20 years. So it serves us well to consider all the various interrelated, underlying comorbidities associated with the diabetic lower extremity. Again we talked about neuropathy, not just sensory neuropathy but motor neuropathy and autonomic neuropathy. How autonomic neuropathy relates to microvascular disease and sympathetic failure. How macrovascular disease which is what we're talking about here at PAD can complicate everything and complicate that high-risk, neuropathic deformed foot that leads to ulceration and infection in the presence of trauma and ulceration and subsequent gangrene. So it serves us all to think about all these underlying problems because it portends a very difficult patient to manage and if we're going to effectively manage these patients, you need to have a good thorough understanding of what's underlying in their problems. So we're gonna talk right now about vascular disease. We talked a lot about neuropathy earlier. But vascular disease is our concern at this point and primarily large vessel disease or macrovascular occlusive disease, arterial occlusive disease, what we commonly call PAD. This paper by Propers who's published in 2008. This comes from the Euro-Diab, or excuse me the Euro Dials Study which was a European study of 14 recognized diabetic foot centers. As I said in Europe, where they did a prospective cohort study where a thousand patients with DFU and they followed them for one year and assessed predictors for healing or non-healing. So the study was over at one year's time. And they examined the difference between patients with or without PAD. They diagnosed almost 50% of their patients at presentation with the DFU, almost 50% had PAD. Infection was present in 58% and PAD and infection, 31%. Now at one year, 23% of these people had not healed. These are unadjusted odds to ratios here, but as we can see PAD 2.31 over two-fold increase risk for not healing infection and PAD with infection, almost a three-fold risk for not healing. So PAD and infection, very tragic cohorts for preventing healing and often they only follow these patients for a year so many of these patients would have gone onto amputation as well if they remain non-healing.


    So it really just portends the importance of PAD and managing these patients and I mentioned another European study earlier today. Stephan Morbach’s study where the most significant predictor for amputation in his 10-year study was of course Peripheral Arterial Disease and the mortality effects of PAD in these diabetic patients. I think you should all be aware of the comprehensive diabetic foot exam paper that was published in 2008 by the American Diabetes Association, Andrew Bolton was the lead author on this paper and it was a multi-disciplinary task force that I participated in. And what we said for the key components of the diabetic foot examination, derm-, musculo-skeletal-, neurologic assessment but also vascular assessment. And this is where many people fail including residents including my own residents and students because many residents and students can take a pulse on a table, feel their own pulse. What we said and what has been said earlier not by us, was that it's a worn skill, especially when the pulses might be weak or when you have an edematous foot due to CHF or what have you. So also we recognized the importance of getting in ABI, Ankle-Brachial Index, recognizing fully well the shortcomings of ABI but just think about the strengths of an ABI when it's below normal. It's below normal and you’ve diagnosed somebody who otherwise might not had been diagnosed with PAD. In this last panel that we see just are risk classification scheme where we’ve kind of modified the VA pattern, the international working group risk categorization, recognizing the important role of PAD with or without loss of protective sensation. And really usually, this Category 2 should be loss of protective sensation with or without PAD. When you have PAD in the presence of neuropathy and protective, loss of protective sensation, you’re at elevated risk, obviously for ulceration, and gangrene infection, etcetera. So you should be familiar with this paper as well as different categorization schemes for diabetic risk categorization. So let's talk more about Peripheral Arterial Disease and this is not an exhaustive talk unfortunately. But I think it's certainly important so over a year, over our break I just put together some, what I figured important things for you to consider. We're all aware, I'm sure in this room of various non-invasive arterial studies that we can order. ABI measurements with and without toe pressures, usually with toe pressures are the baseline measurement that we should always be obtaining on our patients. Pulse Volume Recording, I wanna revive from the past, go back to the future. I think PVRs are extremely helpful and we'll talk a little bit about this later on. Segmental pressure measurements go along with the ABI so you get segmental level pressures, colored duplex ultrasound. We're starting to use more colored duplex ultrasound as a pre-angiography modality to help detect sites of stenosis or sites of occlusions so that they can minimize the amount of dye necessary when we’re doing an angiogram. And then neuro people are using duplex colored ultrasound as a primary way to detect ischemia in diabetic patients as well. Of course Laser Doppler Flux Imaging is more of a research tool, not clinical. All of us have used TCPO2 or Transcutaneous oxygen tensions. And I think skin perfusion pressure using Laser Doppler is actually a far more sophisticated method and I think far more reliable. You can see the SPP curve, down below. Pretty much, pretty much the same as T-coms except more reliable and when you have a skin perfusion pressure of 30 millimeters of mercury or less it predicts wound healing failure. So we're using that more commonly now as well. And then of course, there's quantitave indocyanine green angiography despite technique which I really don't have any experience with and high-perspectual imaging which has been taking off of the market but I'm hoping that high-perspectual imaging will come back because that was a nice regional screening tool to detect the underlying ischemia. Then we have our invasive or pre-revascularization studies, our arteriography, the DSA, MRA or CTA, the computer tomography, angiography, we also have CO2 angiography available for those patients with renal insufficiency.


    So there’s a number of ways that we can diagnose or identify areas of PAD but what we need to know primarily as podiatrists are those areas are non-invasive studies. And what we should be doing and when we should be using those. And I'm very, very much in favor of being over aggressive in terms of getting or at least baseline studies. We always have a baseline to which we can compare because remember these patients are frequent flyers. We see them one month then we might heal them we might not. We see them in the next few months later, or the next year, we always need to have something to compare them to because these people, as they get older, and as more years of diabetes, their PAD is going to worsen. So many people always say, well don't get the ABI because we know that the ABIs are often falsely elevated because of medial arterial calcification in diabetic patients. This is why the ADA in 2003 convened a consensus conference on PAD. And they recommended that an ABI should be performed on a patient with diabetes who's over 50 years of age. Why? Just to get a baseline study. And because they recognize that many times people with impending PAD might be asymptomatic will be detecting at that time prior to the development of gangrene or an ulcer or an infection or what have you. We routinely get ABIs on any patient that we admit to the hospital with ulceration or with an infection. A lot of times for diagnosis of an undiagnosed PAD but oftentimes, even if I have palpable pulses on, I'll just get a baseline so I get formal arterial studies because as I’ve said these are usually frequent flyers for us and I'd like to have some comparative studies from year to year on these patients. And the PAD consensus conference had repeated every 5 years if normal, I tend to repeat them whenever there's somebody that comes back into the hospital or if there's been a change in their condition. Now, I think Nick mentioned earlier in his morning talk the Society for Vascular Surgery APMA consensus documents on management of the diabetic foot. I participated in that. It was a 3 or 4-year undertaking and the several other podiatrists participated in conjunction with the Society for Vascular Surgery. And it was published in Journal of Vascular Surgery in January; I think it was co-published in the JAPMA journal as well. And I'm just isolating what we’ve talked about for Peripheral Arterial Disease and the diabetic foot ulcers. These are patients with DFUs and they made a series of recommendations and used the grading technique to make recommendations based on the strength of evidence. So the first recommendation on PAD and the DFU patients was that patients with diabetes have an ABI measurement performed when they reached 50 years of age. Now this goes right along of course with the ADA consensus document. And then any patient with a prior history of DFU prior abnormal vascular exams, or intervention or known disease have an annual vascular examination in lower extremities including ABI and toe pressures. I'm saying this, that I think you all should all download this document. It should be free, free for all and you should follow this because this is gonna be a new guideline for not just the US but for the world to be following how to approach these difficult patients. Also recommended the patients with an active DFU. Pedal perfusion assessed by ABI, ankle, and pedal Doppler arterial waveforms, and either toe systolic pressure or TCPO2 annually. Now I think all of us, especially those of us who work in a wound care center or have hospital vascular laboratories are free to use TCPO2 as quite frequently. I know I do as well, I've also gone to skin perfusion pressures I think those are more reliable. We all are familiar with the waveform analysis and Doppler pressure outputs that we see on the panel on the bottom right. The panel in the center is what I wanna turn your attention to as well. Those are PVR waveforms. All those waveforms that you see on your usual Doppler output, those are not Doppler waveforms generally unless you're looking at a colored duplex Dopplers. Those are usually your pulse volume recordings and I think I'm relying on those more and more and more now.


    Much more than I had in the past because of the difficulties and sometimes assessing a patient’s ability to heal and the amputation of the forefoot, a toe, or more proximal. But talking about TCPO2s which are probably the most common microvascular assessment of oxygen perfusion. I'm going to refer you to Pecoraro's second important paper. The first one was the causal determinants of limb amputation that was in 1990 May in Diabetes Care 1990. And Diabetes the following year, he published the Chronology and determinants of tissue repair in diabetic lower-extremity ulcers. And the finding was that patients with TCPO2 less than 20 millimeters have a 39-fold increase risk of early wound healing failure. It seems fairly commonsensical, this is the case, but the important point is that if patient has low T-coms which is TCPO2 levels, they're very, very unlikely to heal. And these are the ones you that need to move right over into your vascular surgeon's hands so that they could do appropriate investigations, diagnosis, and management of these patients. But you should all be aware of these papers as well because it was one of the first that really, really, became associated with early wound healing failure in diabetic patients. Now I’m gonna move on to Pulse Volume Recording because I think those of you haven't been trained in Boston at the Deaconess Hospital like several of us in this room had been. Give the PVR waveform short-shrift. And I think it's a very valuable way to assess macrovascular flow into an extremity and I say that because the PVR is unaffected by calcified arteries. It was really a volume displacement with a systolic pulse on the foot. There's a volumetric expansion. And the PVR cough which is like a normal dismography cuff or blood pressure cuff just expands and these expansions are recorded. And I find them useful in assessing inflow to ischemic feet, as I said always provide a concurrent with your ABIs. Almost all tests with ABIs gave you the waveforms which are actually PVRs. And it's a qualitative waveform and you can interpret it qualitatively but actually quite easy. As you can see on the top there, that's a PVR waveform, somewhat diminished but still it's a not a bad waveform. And I think, I said go back to the future because I'm going back to a paper in 1979 and I remember reading early in my career. It also came from Garry Gibbons some of you might know that name, Frank Wheelock, Carl [Horr] [17:53]. They were at my institution in Boston and they looked, this was in the days before TCPO2. They had ABIs, and they had pulse volume recording some of the older people remember oscillometry. PVR has replaced oscillometry. So they looked at 66 diabetic patients undergoing a forefoot amputation: a toe, or TNA array. And they based it on clinical examination. They usually did the procedure which they felt based on clinical examination would heal at that level. Very much like old time doctors, where you had to use the clinical acumen to make your decisions. They all underwent non-invasive testing with Doppler, segmental leg pressures, and PVRs and they analyzed the 55 healed and the 11 who failed. And basically what they determined for the most part, that only 1 out of 27 patients represent where the moderate or strong forefoot PVR failed to heal. So what that means to me, if you have a PVR waveform like you see in this central panel on your study, those patients are more likely than not to be able to heal an amputational procedure done at that level. Hopefully this doesn't sound as rhetoric but I'm using this clinical decision tool every day in my practice. And yes I get the ABIs, yes I have my handheld Doppler so I can listen to the quality of the Doppler signals. Yes, I get TCPO2s. Yes, I might get SPP, but also in my calculus I'm looking at the PVR waveforms. I'm looking if there is a sharp upstroke and the peak, does it have a down stroke with that characteristic dichromic notches you could see, and if that's the case I know I've got good blood flow on that area. This is an old time, not a high-tech test but one that's extremely, extremely useful. So their conclusion on this paper was that favorable clinical science in this, clinical science, that means clinical examination, strongly positive forefoot PVR trace are the best predictors of successful forefoot amputation.


    So I've been using this more and more and more frequently in our practice. Now when we are dealing with more and more ischemic or neuro-ischemic patients and I have to make a decision, will a toe amputation heal? Will a ray amputation heal? Can this patient get by with a TMA or do I need to go to a Chopart or do I need to go to a Syme amputation? Or is there no hope for limb salvage? So I’m using this kind of simplified waveform as my calculus or when I'm assessing patients with PAD. And usually we're pretty successful in making those determinations but of course not always. So let's go back to the Society for Vascular Surgery Diabetic Foot Guidelines. Where now they are talking about recommendations of patients who have DFU with PAD and they recommended revascularization by either surgical bypass or endovascular therapy. That's a strong recommendation with pretty good evidence there. And predictions of patients most likely require benefit revascularization was from the Society of Vascular Surgery WIfI classification scheme. It was published by Joe Millson, Dave Armstrong. I don’t use the WIfI. I think that that doesn’t really matter so much. But what I want to show you is the panel right in the center, it's hard to see but it's Chuck Anderson has published this in the past. And I often use this slide where you can see as you go towards the right the pressures increase based on TCPO2, toe pressures and the ABI in yellow. And as you go up on the y-axis their probability of healing is greater, so obviously as you would say, the higher your pressures, whether it'd be toe pressures, TCPO2 or ABI, the more likely you are to heal. But there's no absolute pressure at which everybody will heal, that Gibbons paper from 1979 also show that. Patients who you expect to heal often don't, patients who you don't expect to heal often will. So it's not clear-cut, black and white, when you're talking about diabetic patients with limb-threatening problems. They also recommend a combination of clinical judgment and careful interpretation of your objective test and of course getting proper angiography, doing appropriate therapy. I am not a vascular surgeon so I can't make the decision. Does this patient need endovascular or open bypass but I think all of us have experienced now that says that more people are not initially getting a PTA or angioplasty or proximal stenting before they’re going to bypass unless they have rather a severe disease. And this is where you defer to your vascular surgeon. From our perspective, my job is to diagnose ischemia in patients who otherwise don’t have a diagnosis of PAD. That's your job as well because we don’t wanna let people out of our hands who have undiagnosed PAD and we certainly don’t wanna operate on people on whom we have no idea that they might have underlying PAD because the results might be disastrous. We have so many in the hospital right now who lost his leg because somebody did a fancy reconstructive procedure for a foot deformity and a diabetic with a history of prior amputation. The tendon transfers, subtalar fusion, guy got infected, he was ischemic, and now he lost his leg. You don't wanna be put in that position because it's not serving you or your patients well at all. This diagram again is kind of busy but this also was published within that guideline as I said freely available and you should be aware of. Just when we have a patient with a diabetic foot ulcer assess for ischemia, infection and neuropathy. That's really what this means. And in yellow you can say assess for ischemia by physical exam, ABI, plus TCPO2 or TBI or skin perfusion pressure and proceed with imaging if indicated. If they have severe critical endo ischemia or significant drops in their pressure then you move on to your angiography. In clinically significant PAD, you need some type of revascularization. Obviously you would expect this from the Society of Vascular Surgery but it's a good coalescence of what we now know how to approach the management and diagnosis and management of diabetic patients. So again I would refer you to that document because I think it's gonna become one of the guidelines that are often used in assessing appropriate management for a diabetic feet. So what are the basic tenets of limb salvage2016? I don’t think they've changed. Certainly not in the last 6, 7, or 8 years. Understand the disease, early and aggressive management is key.


    Pay attention to the basic tenets. Treat infection early and aggressively. Diagnose and treat ischemia with early referral, early angiogram, and early revascularization when indicated. That allows us to do foot-sparing surgery like bone resections like partial foot amputations or what have you and save the person's limb. Our job is to save legs. The hardest part is knowing when to give up and when to move on, but our job is to diagnose ischemia so that we can save the limbs by doing partial foot amputations or reconstructive procedures. Proper practice of prevention with therapeutic footwear, podiatric care, education critically important these had not changed at all. And of course multidisciplinary management. The first person who practiced multidisciplinary management was Elliott P. Joslin. Back in the 20s or 30s so it's nothing new. There's nothing new under the sun. It's just now we understand these things further and now people have recognized the important role of multidisciplinary management in these patients. So in summary, going back to Joslin, he also said in his classic 1934 paper "Consequently, it has been forced upon me that gangrene is not Heaven-sent but is earth-born". Meaning if you understand the underlying pathophysiology, know how to diagnose the pathophysiology or metabolic perturbations, the PAD, the infection, and intervene early and aggressively, you'll be much more successful, have much better outcomes with these very difficult patients. Okay. Thank you very much. Hopefully that was of some use to you all. Okay. Thank you.