Occluded lower extremity arteries with significant calcification can be challenging to treat. Pedal access beginners may be intimidated by severely calcified vessels, however, use of the appropriate tools can help increase confidence. Vascular surgeon Dr. Jim Melton and interventional radiologist Dr. Blake Parsons discuss their preferred pedal access tools and techniques and offer some pro tips for those just starting out with pedal access.
We’ve provided the highlight reel below, but you can listen to the full podcast here.
The BackTable Brief
Frequent practice and good ultrasound skills are key in mastering pedal access, according to Dr. Parsons.
Dr. Melton prefers to use braided sheaths by Merit or Bard and a hydrophilic wire. His pedal cocktail consists of 400 units of nitro and 3,000 units of heparin.
Both Dr. Melton and Dr. Parsons report minimal complications with pedal access. Compartment syndrome, dissection, and rupture are rare. When there is concern for a high risk patient with significant calcification and stenosis, Dr. Parsons notes he always preps for groin or femoral access and will consider performing the procedure in a hospital rather than the OBL setting.
Image Courtesy of Sabeen Dhand MD
Disclaimer: The opinions expressed by participants of the BackTable Podcast belong solely to the participants, and do not necessarily reflect the views of BackTable.
Pedal Access Tools & Techniques
Pedal access is obtained through either the AT or PT, depending on ultrasound findings and what is open. Next, a micropuncture set with a short needle is used to stick the vessel, and the pedal access sheath is placed in the vessel over a wire. Dr. Melton prefers using the Terumo glidewire and Merit or Bard sheaths. The pedal cocktail consists of 400 nitroglycerin and 3,000 units heparin, without any verapamil. A small amount of contrast is injected below the knee to visualize the vessels. The wire size is then determined from this, whether it is a .035 glidewire or .018 command wire. Angiography and intravascular ultrasound are performed, as indicated. The pedal access site is closed by injecting some nitro at the end via the sheath, doing a retrograde run, and holding pressure.
Let's walk through a typical pedal access case. Assuming decent vessels, whether it would be AT or PT, where do you like to stick for your pedal access?
First off, obviously, we're using ultrasound. From an ergonomic standpoint, the PT's a little easier to work with. But, that is all just based solely on what changes we're going after, what's the preclinical evaluation, what we think is open prior to getting in there. You can always be fooled by distal collaterals that reconstitute the distal AT, PT, DP… you get a monophasic signal and you think it's open and then you get another case and it's not. So, it just kind of depends.
So, once you get access, walk us through a little bit of your step-by-step in terms of micropuncture set, sheath size, and pedal cocktail.
The Terumo glide sheath is what we used when we first started, pretty much exclusively. They're high end sheaths, a high end company, but at the end of the day they're not braided as much as you really need for pedal because they kink a lot. This doesn't keep you from getting the case done, you just have to use a dilator a lot, back in and out, in and out. We found a Merit sheath and now there's a Bard sheath and both are braided. The Bard sheath is marked really nice on the tip. Merit sheath is a really good sheath too. We don't use long sheaths. We just use short sheaths in the foot. We go in with a micropuncture set with a short needle. We use short needles instead of the long ones. It's just a little bit easier to not come out of the vessel when you hit it and you're trying to get the wire in. A hydrophilic type wire is usually better with a little bit of support on the back. All the micropuncture sets are a little different so you've kind of got to find the one that's a sweet spot for you. Once we get in, we put in either a 4/5 or 5/6 Merit or Terumo or Bard sheath in, depending on our clinical exam and what we think is going on. And then we put a cocktail in that's about 400 units of nitro and 3,000 units of heparin. We just haven't seen an advantage in using any other drugs in there like they do for radial cocktails.
We don't put verapamil in.
Then we usually take a shot with 3cc of dye below the knee and then we go after the clinical findings and what we think we're going into which is, most of the time, very ugly vessels.
Welcome to the south.
From there, there's definitely certain wires. Everyone's got their kind of particulars. Based on that initial shot, is it all below the knee? Is it involving more proximal and the below the knee is not too bad? That will kind of depend on what size system we go with, like with the .035 right off the bat or an .018. So, we're going to start with an .035 glide. Am I going to start with an .018 Command wire and then, obviously, take it up from there. We'll get wire access all the way into the aorta. And then, depending on the patient's creatinine and those things, we'll do an angiogram through the catheter back down the leg as well as an intravascular ultrasound. Not only can we see the extent of the lesion but also we can see and get appropriate size measurement of vessels for angioplasty, potential stenting, and plaque morphology so we can decide, if we need to, what type of atherectomy system to use. We're fortunate enough here, since we're not in a hospital system, to have all the bells and whistles that we want. So, we have a lot of options that we can tailor to each patient's condition.
How do you close pedal access?
I think both of us, we typically give a little nitro before... at the very end of the sheath. At the very end we'll do a retrograde run to the end of the sheath to make sure the tibials still look good and everything's nice and open. Then, we typically give some nitro just for dilatation purposes and then, I would say, the mass majority of the time they just hold pressure. We'll take the patient back to the room. The nurse will then pull the sheath there. Then we're continuously monitoring with valve pressures being held with Doppler, distal, making sure that we've got flow, just like if you're holding up pressure on a fistula or something. We obviously don't want to be occluding it.
Pedal Access Pro Tips
Highly calcified vessels can be challenging and intimidating for the beginner. Dr. Parsons emphasizes consistent practice and developing good ultrasound skills. Both Dr. Jim Melton and Dr. Blake Parsons report minimal complications with compartment syndrome, dissection, and rupture when utilizing pedal access being extremely rare. While spasm may occur upon access, causing poor circulation in the foot initially, Dr. Parsons reports that waiting a short period for the spasm to resolve is oftentimes enough to restore strong pedal pulses. Applying some nitro paste over the access site and waiting 15 to 30 minutes may help mitigate spasm.
Any pitfalls to getting access? Anything that you've experienced a lot early on that you kind of were able to work out that you could suggest for a young guy trying this?
I think for IR guys it's not really much different than sticking a radial artery. Obviously, there's a huge radial first movement so most IR guys are doing a lot of stuff from the wrist. It's not much different, both from a depth standpoint. Now, from the posterior tibial, kind of the more proximal up the leg you get and depending on the amount of calcification in the artery, it can get a little more challenging because that thing's going to roll around on you quite a bit. So, in that, it just takes some practice. AT's are a little easier because you've got the tibia right underneath it so you can kind of pin it to it. But, definitely, the more calcified the vessel is, it's going to give you a little more challenge. A lot of it's just practicing and developing good ultrasound skills, actually seeing the needle tip enter the artery and not just watching tissue move and hoping that you're over the top of it.
If you can get a lot of tumescence in there with the local anesthesia it sometimes stabilizes that calcified vessel so it doesn't roll on you as bad. That's a little bit of a trick sometimes.
For one of my first pedal access cases I did, the thing I was worried about, because the DP was so diseased, was going higher and higher into the AT and potentially causing compartment syndrome or something if my access site was bleeding. Is there anything, any worries like that, of going too high in the AT or PT?
You can. I've had one compartment syndrome out of all those cases that I just fixed here at the OBL with local anesthetic and stuff. I did a fasciotomy and they did fine. It was AT distribution, so it's always a little concern. You have to just clinically watch. If you go halfway up the leg on the AT, the other halfway up is about the same depth so we just try to stay at halfway down on AT.
When you're putting those larger sheath sizes in, are you keeping an eye on the clock and kind of making sure that you don't have that pedal artery occluded for very long before you decide to change access sites for whatever you're doing?
Well, I think you're going to find arteries occluded regardless. You'll do a shot through the sheath and you'll get collateral flow, distal to the sheath, that you can see that's still open. That's what we're obviously monitoring and how much heparin we're giving during the case as well as the nitro and all that, trying to minimize any kind of thrombin. You're going to be occlusive, especially when the average size is probably a three in a tibial. They're a hell of a lot smaller than that whenever you first start and highly calcified. And we know there's going to be inflow disease. I have them prep the groin as well just in case of an emergency. We have a whole team that knows everything that's going on... if we have a concern for a rupture, we've got everything already waiting, ready to rock and roll. Luckily, we haven't really had any issue with that. I know the iliac thing freaks a lot of people out, especially trying to do it from the foot. If it's a case that's really high risk, heavy calcium, super stenosed, there's a very high likelihood you're going to crack something and have an issue. That might not be a case that I'm going to do here. I'm going to take it to the hospital and I'm going to make sure that we have the support that we need and get femoral access still and do that. We're not complete gun slingers. The patient's health is still always at the forefront of what we're doing and making sure that what we're doing is safe.
Okay. So, in terms of other potential complications, dissection, spasm, and we just mentioned basically rupture or bleeding, are you finding those less common, very rare? It's something to be, obviously, careful about but any suggestions to help prevent spasm or dissection?
We use nitro pretty liberally around here, both on initial stick and in our cocktail, but also on the way out. You'll get spasm in an artery that you accessed. And then there's times you'll, say, pull the sheath and they're holding pressure and you come back and their foot is not looking super great. You try to put a Doppler on it and you're not hearing much. That's because you get spasm right at the access site. Most of the time you give it 15 minutes, come back, and their foot's perfect flow and you've got a bounding signal. I've had maybe three times where I put a little nitro paste over the top of it, where the access site was and same thing. Fifteen to 30 minutes later, the patient's doing great. Pulses are great all the way down into the toes. Other than that, I haven't really had too much of an issue. Obviously, we have a ton of ESRD and diabetes patients here, so a lot of calcified disease, tibial arteries, to begin with. From a dissection point, not really unless we're purposely... we try not to go subintimal if we can, especially in the tibials. I just don't feel like they stay open as long. But sometimes it's inevitable. Most of the time you're able to cross intraluminal and stay intraluminal.
And so what do you guys do about pedal loop revascularization? Are you going up and over from AT to PT? How are you guys handling those kinds of cases?
A lot of times, just like you said, either you stick the AT or PT and then go up and over and down the opposite, all the way down into the foot and into the pedal loop. If I can't for some reason, if their anatomy is too steep or I can't get a good mechanical advantage on it, then that's when I'll probably stick the patient antegrade femoral or SFA and then come that way. But, most of the time, we're able to do it from that PT access and come up and over and treat everything from that. And we found some certain catheters will make it easier to get... because a lot of people will say, "Well, how the heck am I going to get up and over?" We have a 90 degree Berenstein that will clip and make it shorter...It hasn't really been much of an issue, honestly, getting up and going back down the opposite artery and then getting treated what you need to.
Dr. Jim Melton is a practicing Vascular Surgeon in Oklahoma City.
Dr. Blake Parsons is a practicing Interventional Radiologist in Oklahoma City.
Host Dr. Aaron Fritts is a Co-Founder of BackTable and a practicing Interventional Radiologist in Dallas, TX.
Cite this podcast:
BackTable, LLC (Producer). (2020, June 22). Ep 69 – Retrograde Pedal Access [Audio podcast]. Retrieved from https://www.backtable.com/podcasts
The Materials available on the BackTable Blog are for informational and educational purposes only and are not a substitute for the professional judgment of a healthcare professional in diagnosing and treating patients. The opinions expressed by participants of the BackTable Podcast belong solely to the participants, and do not necessarily reflect the views of BackTable.
Special thanks to our sponsor:
RADPAD radiation protection