Good evening, everyone. Good evening. My name is Laurie Lozansky, and I'm the chairperson for the SVU eLearning Educational Committee. With the start of the new year, I just want to take a minute to restate the mission of our committee for everyone, which is to offer at least six webinars on cutting-edge topics for SVU members during the year, and we want to feature a variety of knowledgeable speakers. This year, besides cutting-edge, we're going to try to cover topics from head to toe, like literally. So, to put our best foot forward at the start of this year, we have a very dynamic speaker, Ms. Jill Somerset, who's going to present on infrapotential and pedovascular ultrasound. Before we begin, I have a couple of notes from the SVU office to share with you. First, this webinar will be recorded and available online for attendees through the SVU website at no charge in the near future. Moving forward, SVU will be using Zoom for our webinars, so many of you may be more familiar with how to use this program already. I'm going to ask that you please use the Q&A feature, not chat, not raise your hand, to ask any questions that come to mind during this presentation, and then at the end of the presentation, we should have some time for discussion, or we may pause in the middle of tonight's presentation if we have a lot of questions for Jill. To receive your CME from tonight's lecture, you're going to need to wait for an email from the SVU office containing an evaluation. You should get that email in about seven days, so wait for the email, and when you get it, complete the evaluation, and then your CME certificate will automatically pop up. So, that's it for announcements, so let's begin. Tonight, we're honored to have Jill Somerset as our speaker. Jill has dedicated much of her clinical time working towards the development of tools and skills that we can use in our profession, such as fetal acceleration time, and all to help decrease the rate of amputation for patient population. Jill is currently the technical director at Advanced Vascular Centers in Portland, and she also works at Hope Vascular and Podiatry in Houston. Before that, she led a multidisciplinary limb salvage program at PeaceHealth for five years, worked in other practices in the Vancouver, Washington area, and Jill has over 20 years experience with a deep interest and passion for CLTI, or chronic limb-threatening ischemia. She teaches and works with others from around the world. She's dedicated time to research, has many publications to her credit, speaks frequently at meetings, and even has posted YouTube videos on limb salvage. So, a short list of Jill's contributions to SVU now include serving on the SVU Board of Directors and chairing the SVU Annual Conference in recent years. In 2022, Jill was awarded a fellowship from SVU honoring her contributions and service to the profession of vascular ultrasound. Jill spends her free time outdoors, and if you didn't already know, she has a side hustle as the owner and designer of Flow Socks, which are colorful socks, you've got to check them out. They're stitched with vascular anatomy, which she created to build a sense of unity among specialists for limb-saving salvage programs, or maybe just for plain vascular geeks like us. So, yeah. So, please, if you will, join me in welcoming our speaker tonight, Jill Somerset. Well, thank you, Lori, for that very nice introduction. And thank you, Missy, and really the SVU for the opportunity to share some information on infrapopatile and fetal duplex scanning. I'll go ahead and share my screen, but I wanted to thank all of the attendees for really taking time out of your evening. I'm sure all of us had a busy workday, so I really appreciate you taking the time to join us for this call, this webinar. We'll probably take a break midway to answer any questions, and then always happy to share my email if there's any material or questions that I can answer. I always love to talk about cases, so if something's perplexing, always reach out. I see, Andy, you're on the call from Canada. We have talked about cases before, so I love to talk about it. With that said, we'll get started. Here are my disclosures and our CME activity. So the impact of CLTI is huge. If we recall, the mortality and morbidity rate is staggering. When elderly patients have an amputation below the knee, the likelihood of death is three to five years. And when they have an amputation above the knee, it's looking at one to three years. And the healthcare cost, just in the United States, is over $4.3 billion. And unfortunately, if you look at the upper right statistic, 40% of patients in the United States go straight to amputation without even a diagnosis. So we have a lot of work to do globally to address these patients with CLTI and peripheral arterial disease. So vascular technologists, we're really at the forefront. We get a lot of these patients sent right to us first. And therefore, we play an integral role in the multidisciplinary approach to handling these patients with CLTI and even just PAD. So these patients oftentimes now more so come to us with already a contralateral amputation, a forefoot wound, a forefoot amputation. So I feel like I started doing vascular scan in 1999, fast forward to 2025, and these patients are getting more challenging to scan. They're getting younger, and they're difficult. They have a lot of comorbidities. And so these are the patients that I see in the vascular lab, probably similar to what you see as well. And these wounds go untreated, and therefore, to prevent amputation is really challenging. We know that time is tissue. You can almost play out some of the story of these patients that you see over time. The first two pictures on the left and in the middle was taken just two weeks apart. So we have to act quickly and really be involved in the care of these patients. So vascular ultrasound has been around for decades, and we've had these noninvasive tests, ABI, segmental pressures, PVRs, TCPO2. We've had these noninvasive tests for decades. And of course, lower extremity arterial duplex, but really stopping at the level of the ankle. And in 2017, I started scanning my own foot and realized that we can see these pedal vessels with duplex ultrasound, and it really has become a valuable tool in patients like this that you see on the far right, is our other tools may not help us to determine what the perfusion is like in the foot. However, I'm not here just to talk about PAT, because I really believe in a tailored approach to the patient in front of us. A lot of these tools, PVRs, segmental pressure, they have a role, no doubt. However, when we now take a look at these patient population that are diabetic, have renal failure, have a forefoot wound, now we can insert a new tool such as pedal duplex imaging into our algorithm and really into our toolbox to assess the patient right in front of us. Because these patients deserve higher level testing. These patients oftentimes can't undergo the traditional ABIs, or maybe they're false, or they don't have any toes for toe pressure. And maybe you don't have TCPO2. So in this webinar, we'll talk about infrapopliteal, but a lot of it is inframalleolar scanning as well. So I'd like to highlight a couple of publications. This wound zone paper was published in early 2024, and this was 188 global authors of all specialists, podiatry, vascular surgery, interventional radiology, and interventional cardiology. And really, you know, highlighting the role of this multidisciplinary approach, but really this concept of a wound zone. So we have a nice, you know, I contributed to this paper to talk about PAT has really gained some global adoption, because we have to be able to scan right to the edge of the wound bed to understand what the flow is like at the wound bed. We don't just stop at the ankle anymore, and these authors all agreed with that concept. And we're getting more and more detailed approach into endovascular techniques in going around the petal arch or evaluating flow in the foot, and ultrasound should keep up with that. So I just wanted to highlight that vascular ultrasound should keep up with the interventionalists or vascular surgeons as well. So when we talk about peripheral arterial duplex scanning, I'm just going to ask you to be flexible in your thinking. I take a modern approach that is a little different. And so this is an algorithmic thinking, in my opinion, to the CLTI patient, and you're almost like mapping the case in your mind. So you know, you think like a surgeon, think like an interventional radiologist or cardiologist, and really this is an art form. I don't believe we live in this proximidistal world anymore, because duplex ultrasound is so good. They've advanced so much. The imaging quality is so good that we can assess far more things than just a peak in an end-diastolic velocity. We can evaluate access for safety. We can look at the cap morphology of an occlusion. We can understand disease pattern, and we can really map the target artery pathway to the wound. And we cannot forget about mapping the great saphenous vein, because we know, based on the BEST-CLI trial and the BASEL trial, that there is a role for open bypass. And I think the pendulum is swinging kind of back towards open bypass, but certainly endovascular is also a very good option. So I suggest everyone read this paper. It's one of my favorite papers, because it tells us a lot about why we take a history and physical. So you can almost predict the disease pattern that you are going to find in the patient right in front of you, because this paper does a nice job at outlining the prediction. So in a non-smoker, long-term diabetic patient, we anticipate the disease to be infrapoplateal and even into the foot, versus a non-diabetic and long-time smoker, we expect more aortic iliac, femoral popliteal disease. So I'm always getting a very good history of the patient's comorbidities, because it lends itself to knowledge of being efficient with your scanning and maybe thinking about what you're going to find as the disease pattern. So when you understand that comorbidities, and you maybe ask them what their A1C is, do they have any osteomyelitis, you unwrap the foot, always look at the wound, you customize your approach. So in this particular patient, what I would call regional ischemia, this patient has really terrible flow to that fifth toe. Flow in the actual petal arch is not that bad. But this is a scenario where we have to think outside the box a little bit and go to the wound zone. And I'm going to talk to you about, you know, my approach to scanning the foot first, getting a sense of what the perfusion is like, and then finishing the lower extremity. And you'll notice these diagrams that I create. They're very helpful. It's a visual representation, basically, of the target artery pathway to the wound bed. And in this webinar, we're going to talk about the communicating arteries off the perineal artery. And then you'll always see, generally, a GSV mapping because maybe this patient would be better suited for a distal bypass, maybe not. But that's not up for us to determine. But we can save time and map the GSV in the same setting. Now I will say that is also, that's an internal conversation to have with your medical director to write it into your policy. So just be thinking about that. It saves a patient time from coming back. So before we get into the infrapopliteal and inframalleolar scanning, I just want to just highlight, like in my brain, how I approach these patients. So I'm always going to start at the foot. Now we can absolutely do your other diagnostic tests like ABI and TBIs. This is just my approach. So we're going to start with petal acceleration time at the wound bed. And you're going to complete scanning the entire petal arch. Once you know that this perfusion to the wound beds is very abnormal, this would be class IV PAT, and we'll talk about the criteria. Once you know that the perfusion is that reduced, it's going to change my approach to how I'm going to map this patient because this is ischemia. And if it is a class I PAT or normal, it's a neuropathic wound, that's a very different mindset of how we're mapping the case. So when we scan the foot, we understand flow dynamics around the petal arch, which we'll talk about, and then the communicating arteries off the perineal. You'll see my red line here showing that the anterior tibial artery is occluded, that the hemodynamic pathway to this wound bed is actually through the communicating artery on top of the foot through the second dorsal metatarsal artery. So you can almost map the pathway of how we're going to get blood flow to those wound beds. And then, of course, the infrapopliteal detail and possible petal access. And then I'll run through these real quick because it's not quite directed at this webinar, but we can give a lot of information about cap morphology, endovascular approach, what is the safety? Is the common femoral anterior wall clean for a closure device? So there's so much information that we can provide to the vascular specialist, vascular surgeon before they even walk into a case. And then at the very end of this webinar, I'm going to talk about disease pattern recognition for possible deep venous arterialization, or DVA, as some of you may have heard about. So with infrapopliteal duplex, I'm probably going to tell you, say things that you probably already know, just highlighting that we have a plethora of probes now at our disposable. When I started in 1999, it was on a mechanical scan head on the old ATL. Now we have all of this variety of probes. So use it to your advantage. And you may need to even use the curvilinear probe as we'll pull that out in that TPT region. So when you know the comorbidities, and you can almost anticipate where the disease pattern is going to be, I like to think about isolating the disease. So in a non-smoker and a long-term diabetic, I bet you the flow is going to be probably multiphasic all the way down to the pop. And maybe this patient has a non-healing wound with class 4 PAT or decreased toe pressure. You've isolated the disease. And even if you can't give all the details of the tibials, you're at least telling the physician that you're isolating where the disease is. So it's like efficient scanning. So I scan pretty quickly all the way down to the pop. And then I slow way down and take my time where it counts, which is infrapoplateal and even inframalleolar into the foot. As we know, these tibial vessels can be really challenging. So I don't waste any time proximally. I actually go distal right away and work my way proximal, which is probably what a lot of us do, especially on these patients with large calves. And that TPT can be really challenging. So externally rotating, asking the patient to kind of shift on their hip and imaging that vessel as best as you can, and I know it's difficult. And then for the TPT and perineal, again, sometimes I'll just automatically switch to either a curvilinear or a lower frequency probe like this 7. And then I'll show some imaging here. I like to scan the perineal artery from a lateral approach. You know, I was taught to scan medially for the perineal artery. And honestly, I think the lateral approach is quite nice. And that's where we're also going to see one of the communicating arteries that connects the AT to the perineal artery. And then you can really get fooled with all of these collaterals in the calf, as you know, with the tibial. So always just following that paired vein to prove that you're on the native tibial is really important. So again, this area we know is difficult. So even if you can't see it, you can triangulate and isolate the disease and make an indirect suggestion of hemodynamically significant proximal disease. You know, I think that is okay in some situations. So here's an example of that patient that we saw earlier, non-smoker, diabetic, and it's exactly what we would anticipate, multiphasic flow down to the level of the popliteal. And then I'm gonna slow way down and see we see all of these tandem lesions down the perineal and the anterior tibial artery. And so we can look at vessel diameter, we can see vessel dominance. This perineal artery is pretty small and this anterior tibial artery is much more robust. So I'm also looking at sizes and thinking about the preferential or more dominant tibial vessel that's feeding the wound bed. And if you look at this pathway to the wound bed, if we can just, atherectomy balloon angioplasty, perhaps this anterior tibial artery will indirectly get flowed to the wound bed through the second dorsal metatarsal artery. And yeah, we're probably gonna go in there and clean up the TPT and perineal, but we can probably leave this secluded PT. So a lot of work in the tibials, I think sometimes can be, it's okay to be indirect. So these are some of the, just the tips that I like to give others that I speak with that, sometimes we see retrograde flow in the distal tibial arteries and that's fine. It's probably, it's an indirect suggestion that there's a hemodynamically significant proximal obstruction. And the reason it's retrograde is from a communicating artery from the perineal artery. So when you see retrograde flow, you know that you are going to find some proximal hemodynamically significant obstruction. And I'm always paying attention to the tibial velocities. You know, obviously this distal perineal velocity of 6.5 is really abnormal. So if you cannot isolate the disease, at least we can comment that the velocity in the tibial vessels is abnormally low. And then if you look through the image here, you can see the, this is a communicating artery, but we see a perineal vein with the artery. And so I'm always looking at the calcium burden and the vessel diameter as well. And I feel like the anterior tibial artery is always can get you because there is so many collaterals. I mean, this can be really challenging in a setting of diffuse infrapopliteal disease. And you can get fooled thinking that you're on a patent anterior tibial artery and really it's just a collateral. So just be really mindful to follow that anterior tibial vein right next to that anterior tibial artery because it can really fool you. And I think, again, it's okay to say questionable functional occlusion, poor visualization, or maybe you just can't see, but we've answered the question of this patient. This patient has class four, very poor flow to the wound bed. They have multiphasic flow in the POP. So we've isolated the disease for the interventionalists. And of course, always commenting on calcium burden. While you're down in the distal tibials, always looking at the health and diameter for possible pedal access. More and more operators are really good. We're going retrograde and doing a pedal access, whether it be the anterior tibial or posterior tibial. So I'm always grabbing a AP diameter of the distal tibial and then looking at what the plaque morphology is like. So while you're there, just do a quick diameter. Maybe the vessel is hibernating, but if this is what we need to access to get through this CTO cap, here's the occlusion, they can certainly, you know, these physicians are so good, they can basically stick anything. So give them the advantage of mapping the pedal vessels for pedal access and talk to them, ask them what their preference is. So here's this really nice approach to the perineal artery. Again, for this patient, it started at the wound bed. And then if you go just about two finger breaths above the lateral malleolar bone, locate the anterior tibial artery and just pan laterally, you'll see that perineal artery from this lateral approach. And literally I just slide it right up the lateral side of the shin. Yeah, you might lose it around mid calf and then maybe have to go over to the medial upper calf. That's totally fine. I think just looking at the patient in front of you and being able to switch probes, have the patient move their position and just customize the approach to the patient in front of you to get all of the information that you need, I think is the best advice that I have. So let's talk about the communicating arteries. I think they are undervalued and under-evaluated with ultrasound. And we can see it pretty well. We see it angiographically, but the perineal artery is sort of like the profunda in my mind of the lower leg. The profunda is really the lifeline. Well, the perineal artery in these diabetics is generally in my experience, the last one to go. So the perineal artery has multiple branches, the communicating arteries. So the inter communicating artery connects with the anterior tibial artery. The posterior communicating artery connects with the posterior tibial artery. And there's some other branches a little bit lower here. But once you understand these communicating arteries, the flow direction can be bi-directional. It just depends on the demand of flow, just like kind of the circle of Willis. Think about this is TCD of the foot. So once we understand the status of the communicating arteries, we'll understand more about the hemodynamics around the petal arch. So here's what we see angiographically. This is a very thready, atretic perineal artery, but you can see these communicating arteries. Yeah, they're a little tortuous, but I would suspect because the AT and PT are pretty robust here, flow is headed towards the perineal artery. So we see it angiographically and we can see it with ultrasound. And I'm gonna show you how. But I love this type of situation where we have single vessel runoff via the perineal artery, but you have widely patent, nice communicating arteries to supply the top and plantar aspect of the foot. So to image the anterior communicating artery, you're gonna take the probe about two finger breasts above the lateral malleolar bone and image the anterior tibial artery. And I'm gonna slow this down here. So there's the distal anterior tibial artery. There's an anterior tibial occlusion, but you're gonna start to see a little nub and probably some anterior retrograde flow. And then if you just open your color box and increase your depth, you're gonna see this anterior communicating artery communicate right there with the distal perineal artery. So the flow direction here is antegrade flow down the perineal through the anterior communicating artery out the anterior tibial artery right there towards the foot. So it's very easy to see. You can put a Doppler in there, but really I just care about the flow direction and hemodynamic pathway. When you're here, you can appreciate the cat morphology and you start to see this little nub right here. And then this little nub will kind of tell you that there is probably a communicating artery when you see this little bend. This is the CTO cap. And then if you just keep panning laterally, you're gonna see this beautiful communicating artery and here's the perineal. So just a couple of examples. For the posterior communicating artery, you're gonna do two finger breasts above the medial malleolar bone, and you're gonna image the distal posterior tibial artery and just pan a little bit medial and deep, and you'll see the posterior communicating artery, the perineals down here. And so you can see the flow directions going from PT to the perineal artery in this situation. So when you understand those communicating arteries, it's gonna make a lot more sense of what's happening in the pedial arch. So for example, there is no communicating artery to this posterior tibial artery because it's occluded all the way to the common plantar. But look at this, we have antegrade flow around the pedial arch going retrograde through the lateral plantar artery. This tells us that the pedial arch is intact. And then conversely, if you have the opposite situation, you have no communicating artery to the anterior tibial artery, but look, if there was a great toe wound, the hemodynamic pathway would go around the pedial, through the lateral plantar artery, through the deep and arcuate artery out to the great toe. I love indirect revascularization because we now know about this hemodynamic pathway that we can quantify with pedial duplex. And here's a great example of this patient who underwent a first toe amputation, has an occluded anterior tibial and dorsalis pedis artery, but look at this, the flow goes right to the wound bed for complete healing. So I'm gonna pause right there, Lori, before I get into. Yeah, this is a good point. Like, I don't know if you have a slide for it or maybe, maybe I'm sure you could do it with a whiteboard, but why don't you kind of draw out the anatomy, like from the, you know, the distal calf, like around the ankle joint, just so I think everybody is following along, especially like at the distal end of the perineal and the anterior tibial and the, yeah, maybe you can use one of these. And then there's questions about, are there like multiple communicating arteries that you can have, you know, like multiple anterior, multiple posterior, and is the location of the communicating arteries usually around the ankle joint? Yeah, all great questions. When I go into the pedal duplex, I have more anecdotes. You're coming to it, okay. Yeah, that's okay. But let's talk about those communicating arteries. They generally reside right around the ankle, basically, and we all have them. They just like dormant until we need them. And, you know, sometimes angiographically, like there'll be multiple communicating arteries off the perineal to the posterior tibial artery. There's a lower communicating artery to like the common plantar. So it just depends on everybody's anatomy. Sometimes they're kind of thready. Maybe they're just underdeveloped. So, but in CLTI patients, by and large, you can generally see them pretty well. So just look right around that malleolar area. I usually go about two finger breasts above the ankle to see the communicating arteries. Yeah, I've seen them too. Hey, can I put you on the spot and ask you what waveform terms you use for arterioles? For arterioles, do you use tribi-mono or do you use something else? You know, I kind of use it all, depends on the person that's in front of me. Okay, all right. So, you know, more and more, obviously I try to be in line with the consensus paper. However, you just can't take it out of me. I mean, we've been doing this for so long that, you know, I am, yes, I use multiphasic, but I still like monophasic continuous, this low resistance signal. No, I'm probably, it just depends on the person who I'm having a conversation with. Okay, here's a couple of questions, some additional questions. Like if a patient comes with a wrapped foot, do you take the dressing down and then rewrap it or what do you do? Always. So it depends on your center. Right now I work in OBLs. And so it's really not a problem. And I always, or you can grab an MA. What I would suggest in a CLTI patient is in your institution, talk to the medical director. You need to have the support. Like we don't, if I, when I used to work at PeaceHealth, they didn't want me touching anything. That's fine. I would grab an MA, unwrap, rewrap. But I think it's really important to understand and look where the wound is, what it looks like. We can see tissue granulation. You correlate that with good pedal perfusion. You know, we are a part of this multidisciplinary team just as much as anybody. And so I don't want to be blind and just say, I don't see the wound. So if you can, yes, I know it takes time and we're already up against the clock. The patient's got to go to the bathroom or they were late. I totally get it. But I think we do our best. So in your institution, maybe, you know, have a conversation about how you can best utilize, you know, someone to help you with wraps. Yeah. Here's another question. Does the position of the foot need to be a certain way to get the best image? So for that perineal, like the intercommunicating artery, I usually have their foot kind of straight up and down like this. Obviously, if it's flopped over, like, you know, it's going to be difficult. But, you know, I just have the patient put their foot straight up and down. Yeah. Okay. Carry on. Good. So we're going to go into fetal duplex ultrasound and scanning into the foot is more than just PAT. That's just a small component. We are looking at anatomy. We can understand the calcium burden and we know flow direction around the fetal arch. And we're going to get as close as we can to the wound bed. And it explains a lot. Like, look at this patient with this wound that's not healing after a TMA. Well, it's devoid of flow. This patient really has like regional ischemia to this area. So once you can scan and understand what's happening in the foot to the wound bed, it really helps the physician or care team understand what the heck is going on. And yeah, I know we can order a CT, but these CTs are not great in these calcified patients. Duplex ultrasound is hemodynamic. I mean, as we know, it's a powerful tool that we really should be utilizing in a lot of these difficult patients. So fetal acceleration time or PAT. I scanned my own foot in 2017 and have been on a quest ever since. So this is the original criteria that was published in the Annals of Vascular Surgery. And really, PAT is the extension of the arterial duplex. And a lot of people have questions about billing, and we can talk about that a little later. But for the initial arterial duplex, if it's unilateral, it's just 93926 because we can't charge an extra code for the foot. But it adds a lot of value. So PAT is the measurement of time in milliseconds from the onset of the systolic waveform to the peak of the systolic waveform. It's nothing new into the vascular world. It's been well-published in the renals, in the common femoral, even in the carotid. I just applied it to the foot. And so this criteria was based on 499 limbs that were non-diabetic patients that you could rely on ABIs. And ABIs correlates with PAT, but PAT also correlates with clinical symptoms. In our statistical analysis, it broke it down into four classifications. So class one is absolutely normal. Class two is more consistent with long-distance claudication. Class three is more consistent with short-distance claudication or even non-healing wound. And then certainly class four, which is the worst, which is consistent with tissue loss and rest pain. So this is the established criteria. And take a read. This is a really good paper. This is a group that's also done some work correlating PAT to toe pressure, but they did this really nice paper talking about acceleration time. And there's another publication. People are looking at max acceleration time, really the slope. So just be careful not to confuse slope and acceleration time. But this is a good paper to read. Over the years, we have published many papers on PAT, and we continue to publish this work. And I think a really notable landmark paper is my colleagues at PeaceHealth. This was a landmark paper showing that PAT is predictive of limb salvage. This is Dr. Tesso's vascular surgeon. This was in 2017 when we saw this change on the table during intervention. So we now know that a PAT of class one or class two is indicative of wound healing, and that's outside of any major infection. So we have now three total papers showing this prediction of wound healing. Now, fast forward to 2025, and we have a lot more correlation papers to show that PAT is comparable to not only ABIs, but also toe pressure and a group out of Portugal correlated TcpO2 to PAT. So my hope is to get this into the guidelines, because there really is a role for PAT when we can't use our other noninvasive tests. So these are good references and papers to read if you're curious. Last year, you know, PAT is gaining global adoption. These are my colleagues and friends out of Singapore. Really PAT has changed the way we're approaching these patients from El Salvador to Singapore to Spain, across the country. This is the well-known David Armstrong, a podiatrist. This is how we're going to get it into the guidelines, because there is certainly a role. So it's exciting. It's exciting to see PAT being presented on major international podiums by vascular specialists, interventional radiologists, interventional cardiologists. So the publications go beyond just our group and the Pacific Northwest. There's this Australian group and New Zealand group, and hopefully up in Canada, Andy, there'll be some other papers. So Laurie, this is, I think, what you wanted to get at, right? Was this anatomy? Yes. Yes. Yeah. So this is an oblique view. And just be cautious. The literature is a little, well, if you were to look in an anatomy book, it's a little confusing because they almost show two petal arches right in this area. And if you look angiographically, I'll show you a picture, there's just one major petal arch. There's a second superficial arch here connecting the tarsal artery to the medial plantar. But this is what we can see with duplex ultrasound. So when you're scanning the posterior tibial artery, as you drop down below the medial malleolar bone, this is technically the common plantar artery in this territory. And we have these, sorry, the calcaneal branches off the posterior tibial and perineal artery that feed the heel. And then as we drop below into the foot, we have a bifurcation into the medial and lateral plantar artery. The lateral plantar artery turns into the deep plantar. And that's just like esophageal pump. It's just going to meet the arcuate artery. Some people call this the petal plantar perforator, I call it the arcuate artery and deep plantar. But this is in a sense the oblique view of the petal arch that we can scan with duplex ultrasound. And if we look at the top of the foot, one thing to note here in my experience, we see more anatomical variations on the top of the foot. So the dorsalis pedis artery, if you don't feel a DP pulse, well, it's probably atretic or anatomically absent. And in that situation, you can scan the medial or lateral tarsal artery right here. And oftentimes, there are nice little collateral pathways. So just be aware of the anatomical variations on the top of the foot. Now on the plantar aspect of the foot, we have the medial plantar artery that's in line with the first metatarsal head. The lateral plantar artery, which is in line with the fourth toe, you're going to hear me talk about these landmarks for imaging success as we keep going. So here's that angiographic view that the physicians, you know, we see angiographically, we always get a lateral and AP projection. But this gives you a sense of, you know, there's a discrepancy in those textbooks. So this is what we see angiographically. And I will note here that the medial plantar artery is generally smaller in caliber than the lateral plantar artery. However, if the lateral plantar artery is occluded, the medial plantar artery usually stays open and will plump up. So this is a nice view of the anatomy from an angiographic standpoint. And then, of course, this is the, you know, the ultrasound world of what we can see. So I always like to say in a CLTI patient, we have six sites to test in the foot for PAT. The first one is the most important, which is always at the wound bed. And then we can, you can even apply PAT to the dorsalis pedis, that's fine. You can apply PAT to anything below the level of the ankle. But PAT is not validated in the distal anterior tibial peroneal or distal posterior tibial artery. So just be really cautious, okay? Only apply it below the level of the ankle. So in a setting of a wound, we're going to get the wound bed, auriculate, dorsal metatarsal artery, usually the first, medial and lateral, and deep plantar. And this really gives us a comprehensive look at the entire pedal arch. And a lot of people will be like, well, how long is this going to take you? I mean, just, you know, when you're starting out, it's going to take you a little bit. I mean, think about when we first imaged the circle of Willis and, you know, you were confused about landmarks. But once you do it all the time and you practice, you get efficient. So just like anything, you know, you can scan a foot in like five minutes. So it just takes practice. So here's the steps for success. These go right to the wound bed. And if you need to, put a sterile probe on the probe, sterile probe cover. And I don't necessarily scan over the wound unless it's a full thickness wound. I just scan up to the wound. So in this situation, this is the first dorsal metatarsal artery feeding this hallux wound. This is the fourth dorsal metatarsal artery feeding this fifth toe wound. So go to the wound bed. This would be a lateral tarsal artery feeding this lateral foot wound. A lot of people ask about probes. So I typically use about 90% of the time, I would use a standard linear probe, like a 10 to 12 megahertz that I would scan a carotid with. If the foot is really big or has a lot of callus, I'll switch to like a lower frequency probe or if the foot is tiny and thin, I'll switch to a higher frequency probe. So just adjust accordingly to what the patient is in front of you. So when we talk about landmarks of the foot, we all know where the dorsalis pedis artery is. And there's a bone on the top of the foot called the cuneiform bone. You can all feel it on your own foot. It's the highest bone on the top here. That is a nice anchoring point to evaluate the arcuate artery and the first dorsal metatarsal artery. So this is the distal dorsalis pedis artery. Arcuate artery looks like a waterfall and we see this very nice dorsal metatarsal artery going to the first toe. So if you have trouble seeing the dorsalis pedis artery, go between the first inner space web here and scan back up approximately to the dorsalis pedis artery. Just use that same skill that we use in the tibial vessels. You just have to know the anatomy to understand where you are in the foot. Lori, I'm going to pause right there and ask if you have any questions about this because you and I talked about it briefly. Yeah. So I was telling Jill that when I'm teaching students, they often like put their probe down like right under the big toe and they're calling that the dorsalis pedis artery. And per this drawing, it's not the dorsalis pedis artery. It's probably the dorsal metatarsal artery that you're sampling. So that GPA is not as long as you think it is. Yes. Right. So that's something to change up if you're doing. And yeah, I mean, as our imaging gets better, we correct ourselves. And I don't know if you want to say anything more about it, but I don't know how you teach students. Yeah. Well, I think just everyone should just know the anatomy. I mean, back in the day, before we scanned into the foot, we would do like an ABI and you can't get on the AP or AT distally. You can't get on the DP. So what do we do, Lori? We go between the toes, right? Yeah. And that's the dorsal metatarsal artery. And so as long as you understand where you are in the foot and what vessel you're on, I think that's what's important. I think back in the day, we just always called it the DPA, even though we couldn't know any better. But now you've done all this work and you can tell us that, no, actually we were wrong and there's more things going on down there than we thought. Yes. I totally agree. And if you look through this image, I just want you to note, like I can see, I'm using Power Doppler, of course, but this patient has a low calcium burden. I have really nice full color filling. So I'm always looking through the image and in my mind, what is the calcium burden like in this patient? So from here, this patient has been revascularized. I'm taking a PAT in the first dorsal metatarsal artery to this toe. And we have class 1 PAT. And we know that this patient will likely go on to heal that toe wound. Because we take this criteria and we plug it into the classification. Okay. I'm going to rapid fire here. This is the calcium burden that we see with 2-view x-ray. We can appreciate it with ultrasound. There's no railroad tracks and we don't see it on ultrasound. And sometimes we see it. This is the high calcium burden. We see color skipping. We see, you know, this is a high calcium burden patient. So just be aware of that. When we go to the bottom of the foot, this is the lateral plantar artery and vein. So your landmark here is the fourth toe. Just draw an imaginary line to the fourth toe in the midfoot and start compressing. And you're going to see the lateral plantar veins compressing around the lateral plantar artery. From here, you'll turn the probe in a long axis view. Again, line up with that fourth toe. Turn the center of the probe towards the heel so the toes are always on the right-hand side of the screen. Use those veins as your landmark. If you need to like do an augmentation to get venous flow, do it. But generally, you know, we're not doing a proximal mid and distal of the lateral plantar artery. Just one is sufficient. Here's a nice example of the medial plantar artery. Here's a first met head, a little pressure wound. The landmark here is this hallus longus tendon, and the medial plantar artery and vein will be superficial to that. So again, optimize your image, lower the PRF, increase your gain. And this is by far the most important image or slide to accurately measure acceleration time to lower your baseline down, make your waveform really big so you can accurately measure the onset to the peak of systole. So we don't want a small waveform. So Lori, back to your comment about waveform analysis. In the foot, I don't really care what the waveform is. Yeah, we can say this is biphasic, multiphasic. But in these diabetic patients, they lost the vessel compliancy. One would say, well, this is a, you know, monophasic continuous waveform. Whatever we all decide, it doesn't matter. I just want to know what the acceleration time is in this medial plantar artery. So let's talk about some limitations. PAT is not perfect, but we need to understand the limitations of it. So you cannot rely on PAT in the setting of hemodynamically significant inflow disease in the iliacs. This is when everything below the common femoral artery is wide open. So in this situation, PAT, look at the velocity is really low. It's four centimeters per second. But if you measured this, it'll be falsely normal. So in this situation, man, I would use ABIs. We don't need to use PAT, okay? So just think about, you know, knowing the limitations. Here's another one. This is really poor petal perfusion. We almost can't even measure an acceleration time. So anything over 300 milliseconds is really just class four. And then this is probably the biggest one, and this is where a lot of research needs to go into refining this gray zone. So if the velocity is less than five, less than six centimeters per second, that's automatically class four. The patient on the left has an ejection fraction of 15%. The patient on the right, this is ischemic rest pain. This is class four PAT, very, very low flow. So can you go, someone's asking to go back to the previous slide where you correctly measured the acceleration time. Or I think you just showed one, so yeah. This one? Yeah. Yes. Yes. So we wouldn't want to measure from the baseline. You want to measure from the onset to the peak. Now some people are probably going to have questions because sometimes we get that rounded waveform. We don't measure to the center. It's just the onset before it starts to crest over. And that's why earlier I said read that paper about proper technique of measuring acceleration time. Great. Thank you. Yeah. So like here, we wouldn't want to go to the middle of the waveform. It's really just to the here before it crests over. So there is some tech-to-tech variability, just like measuring a triple A. We build in that 0.3 millimeters of variation. Lori may measure this waveform, and I may measure this one, but the thing is we're still in class one territory, so it's okay. This is also a huge problem, is incorrect technique. We have to make the waveform really, really big. So how we report PAT. So number one, if there is a wound, you report PAT to the wound bed. Because again, you can have a decent PAT in the pedal arch with regional ischemia to the fifth toe. So report the PAT to that wound bed. If there's no wound, report out the worst PAT. So we don't average anything. We don't take the best. We report out the worst. And we have a multi-center international paper coming out in the European Journal of Vascular Surgery that will support all of this data. So this is kind of my approach to CLTI patients. This is a modern approach. Start with our standard workup, adding PAT. If it's class three or class four, I'm going to change my approach, always add a GSV mapping, and then I'm always looking for endovascular safety and access. So you almost escalate the protocol based on what you're finding at the wound bed. So we have to think like an interventionalist, think like a surgeon. These are patients that are so complex. So I'm thinking about everything that Dr. Montero-Baker in Houston is going to do with this patient. This patient ended up going on for venous arterialization. There's no option for bypass, and it would be very difficult. So I'm trying to think ahead and plan like a physician. Lori, I'll just go over a case scenario here. This is a 72-year-old male who presented with a one-week history of right toe discoloration and rest pain. His ABI was reported out as one. He's a nonsmoker, non-diabetic. So we saw this patient. Here's the toe. And yes, this patient has a triphasic distal AT. This patient was discharged from the hospital with nothing to do. Now, if we were to scan into the foot or think about this obviously looks embolic, we probably all agree about this on the call. So it would require a full arterial duplex, not just stopping at an ABI. And of course, we're thinking, you know, this patient has a high incidence of a AAA. So definitely going to rule out there's no AAA, and we're going to go find the source of this emboli, which happens to be in the popliteal artery. So yes, multiphasic flow in the distal AT, but this is where the real problem is. Look at this. You know, this is almost like a cradial thrust of a carotid occlusion. This is, you know, an embolic event of that dorsalis pedis artery. Obviously it stopped or silenced. So we're reporting out to this toe. This is occluded. So this would be class IV PAT. Obviously the patient went on for intervention. You can see the abrupt cutoff. This patient has more prominent plantar circulation, as we would guess, because this is now all thrombosed. But you can see this patient has an intact petal arch here, APV, I'll skip through here. So the patient came back. We did refer the patient on to vascular surgery, did a full mapping so they can repair this small aneurysm with lined mural thrombus. But the wound progression happens really fast. So we have to be thoughtful. So he had an open repair, and now he's developed all of these collateral pathways. This is like an AP view of the foot to understand the perfusion to the wound bed. So now it's 72. Even though this is occluded, we have now a nice flow in these tarsal arteries off the AT. And the patient went on to complete healing. So Lori, we have a couple of minutes left. So I'm going to just pause right there. Yeah. There's two similar questions, so I'll ask that one first. Is PAT ever indicated for patients who don't have visible wounds? Is it applicable if there's no wounds? Yeah, absolutely. We use PAT in quadricans, to be honest. I think in quadricans, there's still...

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