Chapters Transcript Video Ultrasound Demonstration Reviewing Pedal Anatomy and Pedal Acceleration Time (PAT) Duration: 13:06 minutes My name is Jill Somerset. I'm a vascular technologist and uh we'll be doing a demonstration for pedal acceleration time and really pedal duplex looking at anatomy, flow direction, and, um, perfusion or hemodynamic measurement, uh, looking at the peak of cystole or the onset of cystole to the peak of cystole. So before we get started we're gonna concentrate first on the anterior circulation. So on top of everyone's foot is the cuneiform bone, and if you feel with your finger, there's a bony ridge between the first and the second toe so you can feel this with your finger and then you're just gonna slide your finger distally between the first and the second toe and you're gonna feel this kind of squishy soft tissue window that's the window that we are going to image the distal dorsalis etus arcuate artery, and first dorsal metatarsal artery. So what we're gonna do is pick up the probe and every ultrasound probe has an indicator um and for orientation purposes, this indicator of the probe is gonna go towards the patient's head. We're gonna start in a long axis view and I always recommend to use a generous amount of gel on the top of the foot because these vessels are so superficial we can easily obliterate them with too much pro pressure. So we're also gonna anchor our fingers, and this goes for any kind of scanning actually so we don't apply uh too much pressure and we have good um traction with the probe. So anchor your 4th or 5th and your 4th fingers to the patient's skin. And we're gonna scan right distal to that cuneiform bone. Now, when we look at the ultrasound image, we're not gonna put on any color. We're only gonna use our B mode landmarks and our B mode landmarks on the top of the foot is going to be the cuneiform bone. Which is on right here, so this is that bone that you can feel the dorsalis peus artery is right up here. So the the landmarks here is the cuneiform bone and the medial marginal vein which we see right up top here. So I'm just gonna optimize my image. This is the deep foot perforating vein. This is the patient's head on the left side of the screen and on the right hand side of the screen is the patient's toes. That's why the indicator of the probe is really important for orientation. You'll also notice this is a soft tissue window. There's no bone on the right hand side of your screen. So if I were to pan my probe medially, look at, I run into bone. And if I pan the probe laterally I run into bone, so you have to stay within this soft tissue window before uh you can move on. So now that I've established my landmarks looking at the cuneiform bone and the medial marginal vein, now I'm going to apply color and you're gonna see this beautiful arcuate artery cascading or water falling down the cuneiform bone. And if we look here. We can see this is probably the 2nd dorsal metatarsal artery because it's deep. Usually the first dorsal metatarsal artery comes off a bit higher and more superficial, and this is OK she probably just has a little anatomical variation and that's OK. I also want to draw your attention to the color scale so because she's young and healthy, the scale can be high, but in a CLTI patient we want to lower our scale. Uh, down to like 12 or maybe even lower in the setting of significant disease. For orientation purposes, flow, um, in the color bar is going away from the probe. This is normally directed, uh, RQ at artery. So now we can establish color. We're gonna put in Doppler, we're gonna angle correct. And obtain uh a wave form in the acute artery. So we're gonna decrease our scale. The waveforms really big now clearly this is a multiphasic, very normal waveform, but um, oftentimes in diabetic and renal failure patients it's monophasic continuous. So we're gonna measure from the onset of systole and all the way to the peak. Now on the ultrasound system, I have a time slope calculation package. And that actually uh calculates the acceleration time you'll see slope here. We don't wanna use that number that's just part of the calculation. We wanna use this time in milliseconds. So if you remember the criteria, class one or normal PAT is less than 120 milliseconds, so she has normal pedal flow hemodynamics with antegrade flow in her arcuate artery. So that's one point where I would get an acceleration time. Now, we're gonna follow her. I'm gonna lower the color scale, and now we're gonna start to get into some little digital arteries as we go closer to her, uh, big toe. Lower my color scale way down you can see she just has a little uh anatomical variation. So this little second dorsal metatarsal artery is actually supplying just a little, just a new little collateral pathway going more superficial. So I'm gonna just follow that little vessel. It takes a little bit of finesse. And remember I'm going towards her toes. But these vessels get really tiny, especially in a healthy young woman. So to be careful, that's a little um vein there in blue that's superficial. So if this was as far as I could follow that um branch I'm almost to her uh great toe. If there was a toe wound. This is where I would take a pedal acceleration time here, so we would call this, this is really a second dorsal metatarsal artery, but we can absolutely um. Get an acceleration time here. And a lot of people ask, you know, if the vessels really calcified, can we, um, get a good Doppler ssy or a velocity and acceleration time? The answer is yes, um, you just have to Doppler in between, um, the like color skipping and where it's patent. So that would be the two sites on the top of the foot for a normal pedal duplex. Now if um she had a 5th um toe wound, I would just place the probe right between the 4th and the 5th toe. I could even switch to the hockey stick probe or a high frequency probe um because she's young, we may not see it, but in a, um, wounded patient we get vasodilatation and these vessels are really, uh, easy to see. Let me see if I can see it on her. Yeah, maybe not just super, super tiny. OK, so now we're gonna go to the bottom of the foot. So the arcuate and dorsal metatarsal artery are the major two anterior vessels. Now we're gonna look here. Um, a lot of people ask if so the distal, uh, PT as it crosses below the, um, medial malleolus has becomes the common plantar, and then it's gonna bifurcate into the medial plantar and the lateral plantar. This is a very difficult area to scan. So I scan to the distal uh PTA and then I just pick up my probe and go right to the bottom of the foot. So the lateral plantar artery is in line with the 4th toe. So that is your landmark. So you want to put the probe in a transverse view just in the midfoot in line with this 4th toe. And now when we look at our screen. We have new landmarks different from the cuneiform, uh, bone and the medial marginal vein. Now our landmarks is the metatarsal bone which is on the far, uh, field of the ultrasound screen, and I'm gonna do probe compressions and look what we see. We see a beautiful big lateral plantar vein that's compressible. Just in the mid midfoot there so that's my landmark. I'm gonna mark that depth with my eye. It's at about 2 centimeters deep and then we're gonna turn our probe in long axis. So on the top of the foot, the indicator went to the head on the bottom of the foot, the indicator is gonna go towards the heel, and the reason is is because we always want the toes on the right hand side of the ultrasound screen. So now in a long axis view you're gonna align your probe with the 4th toe, place the probe. We're gonna do the opposite of the top of the foot. Now we're gonna actually apply pressure because we want good skin contact. So from here we're in line with the 4th toe and now I see the lateral plantar vein and long axis is actually compressible if you can see that. And now I'm gonna apply color and this is where we're gonna see the lateral plantar artery. It's just gonna be kind of smaller in caliber, there it is. Generally, um, pedal duplex is very, is a lot easier in a diabetic adrenal failure patient or a CLTI patient. So here's flow in the lateral plantar artery. Now if I compress the posterior tibial artery. Hold on one second. Um, I like to just, if, if we need to indirectly revascularize. Look at that. I just reversed the flow, so I know that her pedal arch is intact. Let me just show you that again. I'm gonna decrease my scale way down so you can see the flow reverse. I'm gonna compress the posterior tibial artery because right now flow is integrated. flow is going from uh the posterior tibial artery towards the toes. Now if I can press the PT. Now the anterior circulation kicks in and now flow is being fed from the RQid artery. So she has a nice intact, uh, pedal arch that we can indirectly see by used by duplex ultrasound. Now, the medial plantar artery is going to be in the same location in the midfoot, but now I'm going to just slide my probe medially and then the medial plantar lies superficial. So I'm gonna look for this. It's called the um hallis longus tendon and it kind of goes right across the screen here. And that is the landmark for the medial plantar because the medial planter is gonna be way more superficial than the um lateral plantar artery. And there's the medial plantar artery. So the reason why I love the medial plantar artery is because when you have a first met head wound, this is exactly where you wanna go is you wanna actually take a pedal acceleration timer right here. This is like targeted. Hemodynamic perfusion to a wound bed. The other cool thing about the medial plantar in my experience is that when the lateral plantar is the lateral plantar artery is occluded, usually the medial plantar artery will be spared and then this thing will get real juicy. It'll get, it'll die. It's like really nice collateral pathway, um, when the lateral plantar artery is cluded. So her PAT here is also 144. So those 4 we can even get to the deep plantar artery if we really need to see flow in the arch, but to get started, to be successful in pedal duplex, I think looking at the arcuate artery, first dorsal metatarsal artery, lateral plantar and medial plantar are really essential um to becoming successful in scanning a patient's foot and then. It really, it gives you enough information in the setting of CLTI that you can understand the anterior circulation and the posterior circulation when it comes to perfusion and pedal flow hemodynamics. Published December 20, 2024 Created by Related Presenters Jill S. Sommerset, RVT, RSVU Vascular Technologist View full profile