Section: CME Category: Vascular

Early Identification of PAD - A Critical Component of Podiatric Care

Charles Andersen, MD

Charles Anderson, MD discusses the role and techniques available to screen for PAD as well as consequences related to failing to identify PAD prior to podiatric intervention.

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Goals and Objectives
  1. Describe the role of screening for PAD
  2. List the techniques available to evaluate PAD
  3. Describe the limitations of the techniques available to evaluate PAD
  4. Describe the consequences of failing to identify PAD prior to performing a podiatric procedure
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  • CPME (Credits: 0.75)

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    Release Date: 04/12/2018 Expiration Date: 12/31/2020

  • Author
  • Charles Andersen, MD

    Chief of Vascular-Endovascular-Limb Preservation Service and Medical Director of the Wound Care Clinic at Madigan Army Medical Center
    Tacoma, Washington
    Clinical Professor of Surgery at the University of Washington and the Uniformed Services University of Health Sciences

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    Charles Andersen has disclosed that he is a consultant/advisor for KCI, Organogenesis and Stryker.

  • Lecture Transcript
  • TAPE STARTS – [00:00]


    Speaker: So I am a vascular surgeon by trade. I have spent majority of my career at Madigan Army Medical Center. We were fortunate at Madigan over 20 years ago now to identify a problem. The problem that we identified is that we were doing too many amputations in patients with diabetes. As a result of that, we established a multidisciplinary program for amputation prevention and that's been a very successful program over the years to prevent amputation in patients with diabetes. It's in that setting that I have had the opportunity to work with some fantastic podiatric surgeons as partners and also to be intimately involved in wound care during that period of time. My partners have included Dr. Vickie Driver, Dr. Tom Lucas [phonetic], Dr. Valerie Shade [phonetic], and Dr. Mario Ponticello. We are going to start this morning talking about vascular disease and again I appreciate the earlier risers just as a quick summary. Vascular disease and podiatric surgery and wound care are really tied at the hip when it comes to the prevention of amputations in patients with diabetes. So if you are involved in that initiative and everybody in here that's practicing podiatry is going to see those patients that are potentially at risk for losing a limb or losing toes or partial foot as a result of the complications of diabetes. In that setting, it's extremely important to realize that vascular disease plays a major role and many times not the cause of the ulceration.

    [02:09]

    But as a factor that can be a major limiting factor in the ability of that wound or toe to heal and hence a major factor that can contribute to amputation. So the first talk this morning we are really going to talk about the identification of PAD. Those of you that have been here before, this is a talk that I have given before, although I have made some modifications. The major modification is one in philosophy. My partner, Dr. Mario Ponticello a few days ago actually said, you know I went to a Seattle Podiatric MNM where podiatric surgeons from across the state come and they talk about their cases where there has been less than favorable outcome. And his statement to me was the most common cause of complications was the inability or a failure to really identify coexisting vascular disease in patients that were having podiatric procedures. So this is not just about limb preservation. This is also about elective podiatric surgery. If you are doing an elective podiatric surgery and you fail to identify vascular disease, then that can lead to a complication. I have no disclosures. As I mentioned, I am a vascular surgeon with a very strong interest in limb preservation. Key is I work for the government. Like you, I actually work for the Department of Defense at Madigan and what I am going to say is not the opinion certainly of the army, the veterans affairs, it's my opinion.

    [04:09]

    And this presentation is not meant to endorse any products, company or programs. So these are objectives we are going to discuss the role of screening for PAD, discuss the techniques available to evaluate PAD, the limitation of those techniques and then discuss the consequences and I have already alluded to that. The consequences of failing to identify PAD prior to performing a podiatric procedure. So the conclusion of this talk, I will start with the conclusion and I will build the case is the timely and accurate assessment of peripheral arterial disease is an important component of routine podiatric care and a critical component of a limb preservation initiative. This close working relationship is something that I have had the privilege of working over 20 years. And I think as all of us taking care of especially high-risk patients, this is very important partnership to build. This was recognized formally in September of 2010 with a publication that was published both in the Journal of Vascular Surgery and the publication of APMA. And the title was "Strategies To Prevent And Heal Diabetic Foot Ulcers Building A Partnership For Amputation Prevention." That partnership between vascular surgery, vascular intervention and podiatric surgery. And that's where some of you have had heard that term "toe and flow."

    [06:04]

    Identification of PAD, sometimes it can be rather obvious when you see a patient just with a history and physical, but other times the diagnosis of PAD or the presence of PAD can be very, very subtle. Certainly, we would all recognize this patient. This is a pallorous foot that obviously has secondary changes of very significant arterial insufficiency. This may not be identified. I will allude to this several times but when you are called to the emergency room to see somebody with erythematous foot, this may be dependent rubor and may be a sign of critical limb ischemia. Oftentimes misdiagnosed as cellulitis, these patients are placed on antibiotics. So a very simple thing to do is take this foot, put it up in the air and if the color goes away, that's an indication of dependent rubor and it’s also an indication that this is not cellulitis. When we are taking a history in somebody that we suspect may have vascular disease, the first presentation is generally claudication. It's important as you have seen your patients, many of our patients have pain in their legs, so the key is how do we distinguish musculoskeletal pain from claudication. And this is where Warren's criteria can help you with claudication. It's very specific pain with ambulation, relieved by rest and reproducible and consistent. When you take each one of those criteria, it's very, very consistent patient don't have good days, they don't have bad days. It doesn't vary during the day and that pattern of relief when they just stop is critical in making the diagnosis of claudication.

    [08:09]

    Rest pain, many times we have patients sent to us with a diagnosis of rest pain that have some kind of muscle cramp in their calf. Rest pain is something very specific. It's across the metatarsal heads. It's pain these patients generally when they go to bed at night, lose the advantage of gravity, they will then have pain in their feet. They also find that again if they put their feet back in the dependent position that that will relieve the pain. So that's true ischemic rest pain. So rest pain are nonhealing wounds, again as part of the history. The key is and I am going to repeat this multiple times that many patients with significant PAD do not have symptoms, hence you will not pick this up on a simple history. The challenge then especially in our patients with diabetes, many of our patients have neuropathy. Many of our patients are not very ambulatory and can have very, very significant PAD that unless you look for it, you are not going to find it. Physical examination certainly everybody that you see in your podiatric practice, if you are planning any kind of intervention especially palpating pedal pulses, this should be part of the physical examination. If they are not clearly palpable and I spend my time teaching residents and they can feel a pulse anywhere. If it's not clearly palpable, it's an indication to do something else. The simplest thing in Dr. Freiburg alluded to this early on Wednesday morning is just take a hand-held Doppler.

    [10:05]

    The hand-held Doppler, you have to not just hear the presence of a signal but be able to evaluate the quality of that signal. So a normal Doppler signal is triphasic. It's sounds -- a first indication of disease is you lose that third part of the triphasic. So it becomes biphasic. As disease progresses, then it becomes monophasic. So if you have that patient that you cannot palpate pulses and you hear a pfoo, pfoo, pfoo [phonetic] even though you hearing a Doppler signal, that can be an indication of very significant vascular disease. What about routine screening? I had an interesting talk with our chief of medicine a few years ago when we were talking about screening for various types of vascular disease and he said, well, you are just looking for more cases in vascular surgery. When you are talking about vascular screening, in general this is not about procedures at all. Early identification of vascular disease is about identifying a systemic disease, atherosclerosis. And when that disease is identified, that's an indication for treatment. The treatment is medical treatment. The majority of those patients would not at that point in time picked up on a screening exam require any kind of endovascular or open procedure for their vascular disease. ADA recommends screening of vascular patients over the age of 50 with diabetes with an ABI. That's worthwhile.

    [12:01]

    We will talk later about the limitations of an ABI. But again, an abnormal ABI is a good indication of a systemic disease. So it's really not about the legs, it's about identifying disease that can lead to significant morbidity. The most serious part or the most serious morbidity is associated with the heart, myocardial infarction or with the carotids causing the stroke. Same disease, different parts of the body. The key is if you pick up disease on a screening exam, that's an indication to get medicine involved or if they pick up the disease. Again, early treatment -- and there is now evidence that early treatment of atherosclerotic vascular disease from a medical perspective can decrease the progression of that disease and the consequences of that disease. This is an interesting cartoon. I have an ulcer on my foot. Why do I need an EKG? Again if you have PAD, a good chance that you have coronary artery disease and you want to be able to pick up that disease because that oftentimes is the fatal part of the atherosclerosis. When we do vascular surgery, for example, if I do a carotid endarterectomy, the most common complication is not a stroke but most common complication after a carotid endarterectomy is a myocardial infarction, which again indicates it's a same disease in different parts of the body. If I have somebody with critical limb ischemia, by definition those patients have coronary artery disease. If you draw parallel lines with the progression of PAD, the same thing is occurring in the coronary artery.

    [14:04]

    So as the PAD progresses, then the coronary artery disease progresses and again that can be a cause of major morbidity and mortality. I call this cause and effect. Oftentimes, if you have progressive vascular disease, it's like an irrigation system. You don't get flow to the very distal part of that system, so you end up with ischemic toes as demonstrated on the left. On the other hand, if you have a diabetic foot ulcer for example and you have associated vascular disease that can become a limiting factor as to whether or not that ulcer will heal. So in general, vascular disease is not the cause of diabetic foot ulcers, but can be a very significant factor. We all in this room understand the etiology of diabetic foot ulcers. In general, there is neuropathy, altered ability to feel the bottom of your foot, so that's the sensory part of the neuropathy. The motor part, altered biomechanics, hammertoes, equinus foot, so different pressure points and then unrecognized repetitive trauma whether it's pressure or over shear and that leads to an ulcer. Once you have that ulcer, the two factors that are confounding factors that can then lead to higher incidence of amputation are ischemia and infection. So testing for vascular disease, why would you do preoperative testing? The two reasons if you are in a podiatric practice that you do preoperative testing.

    [16:04]

    One is to make sure there is adequate perfusion to heal the operation that you are going to perform. The second thing is to risk-stratify that patient. So if the patient has PAD and you are planning a major podiatric procedure, that patient needs to be looked at as a higher risk for a postoperative myocardial infarction. Hence, when you are weighing whether or not you are going to do a complex podiatric procedure or the perioperative management knowing that that patient may have significant coronary artery disease, you may want to do additional studies to evaluate the degree of that coronary artery disease or certainly manage that patient preemptively to make sure that you control the work of the heart. We oftentimes with our residents talk about tipping the balance. So that in order to maintain intact skin, it requires this amount of blood supply. Once you have a wound, then you have higher demand and if you can't meet that demand, then that would is not going to heal. So this is a patient that had pain in the toe, stopped at a Doc-In-The-Box. The physician there felt that was a paronychial problem, did a fairly simple procedure and that was followed by distal gangrene and ultimately this patient had lost part of the foot. The key is that this pain probably didn't have anything to do with the nail but was an early manifestation of vascular disease. Be aware of doing simple procedures on patients with vascular disease.

    [18:01]

    You can end up with major complication. I already mentioned this that in an MNM, the common cause of complication was a failure to identify vascular disease. There is categories of vascular disease, the Fontaine and Rutherford classification. So going from asymptomatic claudication, ischemic rest pain, major or minor tissue loss. A Doppler signal, we have talked about. So if you are fortunate enough in your office or in the vascular practice that you are associated with, if you can do a recording of the Doppler signal, then you have documentation of the type of signal. A trainer hearer is good. It's good to also have the documentation. An ABI, we are all familiar with an ABI. The problems with an ABI is patients with diabetes have medial calcification. Oftentimes, especially if they have associated renal disease, the vessels at the ankle become non-compressible. Therefore, it gives you a falsely elevated ABI. The other thing that many people don't realize is the ABI measures pressure where the cuff is not where you are listening for Doppler signal. So it's the amount of pressure required at the ankle to occlude that signal. So when you see the printout and it has a DP or PT or peroneal, that's talking about the pressure at the ankle not in the foot. So an ABI normally is 1.6 is adequate perfusion to heal a wound, 0.5 is in general indicative of multilevel disease, and 0.3 is the level where you start to see ischemic rest pain and gangrene.

    [20:10]

    Again, a study showing a normal ABI but on the waveforms indicative of significant vascular disease. Toe pressures are more valuable in the patients with diabetes. Sometimes they don't have toes but certainly if they have toes, then getting a toe pressure or TBI is very useful in patients with diabetes. A normal TBI, the ratio of the arm pressure to the toe pressure is not 1, it's 0.75. A TBI less than 0.25 is severe vascular disease. In general, the TBI greater than 0.75 is a pretty good indication that there is adequate perfusion to heal a procedure. An absolute pressure of greater than 0.55 correlates with the ability to heal. Segmental pressures that's where three or four cuffs are placed upon and down the leg and then pressures measured at each level, that is valuable in identifying the location of the disease. So if there is a 15 mm gradient between those cuffs, that will tell you that there is disease in that segment. So when we have identified the patient with disease and now we are trying to look at where that disease is, then segmental pressures can be useful. A stress test if we have patients that have leg pain and we are not sure it's claudication, we can put those patients on a treadmill.

    [22:01]

    They exercise until they get their pain and while they are having their pain, we measure an ABI. If it's vascular disease causing the pain, then the ABI will be at an ischemic level or lower when they are having their pain. This can help sort out patients that may have pseudo-claudication, for example, associated with spinal stenosis versus patients with true vascular claudication. PVR, again, Dr. Freiburg mentioned that this is a test that he still relies on and it's an older test. But it's still a very useful test in identifying both the presence of vascular disease again looking at the waveform or localizing the level of vascular disease. So it can be a good screen and also can help in identifying whether or not those patients have vascular disease, the degree of vascular disease and help determine whether or not a procedure in the foot will heal. If you get to the point where you know there is vascular disease and now you are trying to consider some kind of intervention, that's where you get in into anatomic imaging, velocity detection, that's so-called Duplex scan. Duplex, many times people don't understand what a Duplex machine is or Duplex scan. Duplex means two, so built in one machine, you have Doppler, so you get a Doppler velocity, which also have B-mode built in the machine. So you can see an image of the artery, you can see whether disease is and then with the Doppler velocity, so Doppler is a velocity detector. You can then determine the degree of stenosis, so that's a Duplex scan.

    [24:02]

    Duplex scanning can be very, very accurate in identifying iliac disease, for example, when you are trying to determine -- you have a patient with disease, you are considering intervention, what level, where is the disease located that Duplex scan is very accurate in identifying aortoiliac disease. When you are treating vascular disease, the bigger the vessel is that you are treating, the better the outcome. So if you are treating aortoiliac disease, there is very, very good long-term outcomes. When you get down to the vessels close to the foot and you are treating distal fibular vessels, the outcome is not as good and the incidence of recurrence is much higher. Duplex can also be utilized to evaluate the superficial femoral artery. Again, this you already know from your other studies that there is vascular disease, this can give you an indication, is it a total occlusion, is it a stenosis and what's the level that can be useful information in planning a vascular procedure? The MRI is somewhat institutional dependent. It can be very useful in identifying vascular disease. You can get false positive. You can over estimate vascular disease at times. CTA is a very, very useful modality. CTA should be reserved for patients that you are really consider in some kind of intervention. The non-invasive studies can give you the information of the presence and degree of vascular disease. The problem with going straight to a CTA is that that's 200 mL of contrast and in our patients with diabetes if they have associated renal disease, then that can be a factor that can lead to worsening of their renal disease.

    [26:04]

    They may require pre-procedure hydration before a CTA. So don't jump straight to a CTA to identify vascular disease, use non-invasive modalities to identify vascular disease. Certainly, a standard arteriogram gives you the best visualization of vascular disease. Rarely do we do an arteriogram strictly for the diagnosis of vascular disease. With the other modalities including Duplex scanning and at times CTA, we generally know where the disease is located, the severity of the disease. So when an arteriogram is performed, it's almost always with the intent to treat. So in one procedure, the patient is taken to the either the operating room if you have that capability or the radiology suite or the cardiac cath lab and standard arteriogram is performed. But then the disease is treated at the same setting whether that's an iliac stent and we are getting to treatment in a minute or whether it's a more distal procedure. You know ahead of time where the disease is. You know what you are going to do. The arteriogram just gives you that roadmap so you can then perform that procedure. So it's done with the intent to treat almost always. So again the conclusion of the first talk is that the timely and accurate assessment of peripheral arterial disease is important not only in limb preservation but is very important in the general practice of podiatric surgery. Two big reasons; one is to make sure if you are doing a procedure that that procedure will heal and if they have vascular disease to realize that they may also have coronary artery disease and are at higher risk for perioperative complication.


    TAPE ENDS - [28:15]