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Tips & Tricks for AV Fistula & Graft Declots

Author Lauren Fang covers Tips & Tricks for AV Fistula & Graft Declots on BackTable VI

Lauren Fang • May 8, 2021 • 333 hits

Arteriovenous fistulas and grafts are dialysis access sites that can thrombose. To restore blood flow in the dialysis circuit, a declot procedure is performed to remove clots and treat any associated stenoses which may be flow-limiting. Interventional nephrologist Dr. Neghae Mawla provides tips and tricks for reducing procedure time, working with two sheaths, performing angioplasty, and using stents vs. drug coated balloons.

We’ve provided the highlight reel in this article, but you can listen to the full podcast below.

The BackTable Brief

• It is not necessary to chase after every bit of clot during polishing. Rotational thrombectomy devices can help, as can aspiration from the sheath while pulling back the Fogarty balloon. For Dr. Mawla, a sufficient polish is one where there is no resistance felt in the outflow.

• Keeping the arterial and venous sheaths at a distance away from each other prevents touching and overlapping. This ensures that flow is not impeded, and it reduces the risk of clot sticking behind or between the sheaths. Dr. Mawla also avoids placing sheaths at or near the cannulation zones and anastomoses.

• To avoid dissecting inflow during angioplasty, Dr. Mawla emphasizes sizing appropriately. He typically does not go higher than 10 or 12 atm of pressure at the arterial anastomosis. He performs short inflations using the up-down technique.

• For some resistant lesions, Dr. Mawla will consider placing a stent graft, either the Viabahn or the Covera. He does not use bare metal stents. A drug-coated balloon (DCB) is another option, particularly for lesions and areas where cannulation occurs and it is hard to stent. Dr. Mawla leans toward the DCB when it comes to treating a resistant thrombus that is likely to lead to repeat declot procedures.

Right thigh loop graft with stented segments at the venous anastomosis and graft

Table of Contents

(1) Aspiration, Devices & Polishing

(2) Sheath Placement and Angioplasty

(3) Stenting vs. Drug Coated Balloons

Aspiration, Devices & Polishing

Aspirating from the sheath while pulling the Fogarty back can help remove additional clot. Polish does not mean the operator needs to chase every little small piece of clot. According to Dr. Mawla, a good indication of when polishing is sufficient is when there is no resistance felt in the outflow.

[Neghae Mawla]
Aaron, you came and spent the day with me. What did you think?

[Aaron Fritts]
I was telling Chris some of the tricks that I picked up. One was the aspiration from the sheath as you're pulling the Fogarty back. That, I had never seen before, and I thought that was a really cool trick. It helped get some of that clot out. You showed how much clot you pulled out. I was used to always just putting the Fogarty back and then letting it flow with everything else, but I think that that makes a significant difference...The official speed by which you do it, and the techs all know your next move, I mean, that all makes a huge difference. Labs that only do [declots] once a month, that slows everything way down because they forget how to set everything up. They're just standing there and handing you wires and stuff, but I think part of it is just well trained staff.

[Neghae Mawla]
Staff makes a huge difference. We always underestimate how important the staff are.

[Aaron Fritts]
With imaging too, right? And then being able to do [the declot] without TPA using the devices. Chris and I trained similarly where I was training just Kumpe catheters, four milligrams of TPA, lace declot as you pull back and then go in and balloon macerate everything. Push it out. Pull with the Fogarty. But I mean, it felt like it took two hours to do a declot.

[Neghae Mawla]
That's the basic declot.

[Chris Beck]
I will say that I get bogged down. For some reason, if I get impatient, I start wanting to do more things myself. I'll start grabbing for things. I'm loading things up on the wire, and that's out of my frustration, but for declots, you really have to be a general. I'll tell my techs before we get started, I'm like, "I'm going to bark a lot of orders, and I'm going to expect you to be on your game. For declots, I really want to move fast." I really stay in one position and let everything come to me because whenever I start flailing around is when I think I get sloppy. The other thing that I learned from Aaron after he went and worked with you, Neghae, was the amount of polish that I'm putting on afterwards. Sometimes, I'm just going after every little small piece of clot. I was just like, "Oh, I don't have to do that," and then it was like someone took a burden off me.

[Aaron Fritts]
Either you watch this little piece of clot, and then you do a run two minutes later, and it's gone, because the flow helps get rid of it, right? You don't have to go in there and balloon every little piece of clot that's hanging on.

[Neghae Mawla]
I take the Fogarty towards the outflow as part of the polish stage... I like the over-the-wire Fogarty because I'll just inflate it and lock it. I'll polish or floss with it. If it goes all the way into the outflow, and I don't feel any resistance, it's fine. If the graft is not pulsatile, and the fistula is not pulsatile, you can get used to examining the fistula after each stage and each step that you do it, and see how that exam changes, because that will guide you also. Then suddenly, you get this great thrill, and all the resistance is gone. Everything feels great. Well, at that point, you can say, "All right, we're done.” You do a quick run to correspond with it, but that becomes a good guide for you also more than the images. If you've got clot, but it feels great, and it's just a little piece of clot that's hanging out, a lot of times... I think that's where my Voodoo for this extra 5,000 of heparin at the end comes in. That should take care of that.

[Chris Beck]
… In terms of getting my procedure time down, if I know which way is inflow and if I know which way is outflow, I will go ahead and place my seven Fr sheath with a seven to six venous and arterial respectively. I'm accessing with ultrasound. I get my seven Fr in, and then also get my six Fr in at the same time. That way, I've just taken care of the sheath work. I've taken care of most of my ultrasound work, and then I can just start going to work on the procedure. But in your situation, it sounds like you're always treating outflow, then coming back, doing inflow, and then polishing up the rest. Is that right?

[Neghae Mawla]
That's it. I will sometimes put in both sheaths just for no reason, but most of the time, before I put that second sheath in, I want to make sure that whole segment is cleared. If that sheath is there, then that slows down how long it takes me, or sometimes it gets in the way of me clearing it, especially if I'm using a rotational device. Balloon, you can do comfortably. You can balloon around the sheath, and it's fine, but if you're doing a rotational device, and that gets in the way, or if there's a wire there that gets in the way, that's why I don't put that second sheath in [immediately].

Listen to the Full Podcast

Successful (and Quick!) Declots for AV Access with Dr. Neghae Mawla on the BackTable VI Podcast)
Ep 117 Successful (and Quick!) Declots for AV Access with Dr. Neghae Mawla
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Sheath Placement and Angioplasty

Preventing the arterial and venous sheaths from overlapping is important, as clot can stick behind or between the sheaths. Dr. Mawla also avoids placing sheaths at or near the cannulation zones and anastomoses. To avoid dissecting inflow during angioplasty, Dr. Mawla emphasizes sizing appropriately. He typically does not go higher than 10 or 12 atm pressure at the arterial anastomosis. His inflations are short in duration and are done using the up-down technique.

[Chris Beck]
There are a lot of anastomoses out there that I think you can spend a lot of time trying to get central, meaning that you cross the anastomosis, it's going distally easily, but it's not able to come up until the brachial artery. You're still able to get the same results just by pulling the Fogarty from the mid radial artery across the anastomosis.

[Neghae Mawla]
Usually, I'll go for the ulnar side, because the ulnar artery is a little bit bigger, but you don't have to get that far. Usually, if it's an upper arm, it's high enough away from the bifurcation. I like going up just because I think it saves me a little step down the line, but if it constantly keeps going distal down the forearm, then I say, "Okay, fine. Let's just do it that way." Do the Fogarty. I always use an over wire Fogarty.

[Chris Beck]
Can you talk about sheath placement and why it's important to have a little bit of physical distance between the tips of your sheaths? What I'm basically talking about is how to avoid the dueling sheath situation where you have overlapping sheaths, and why that's such a pain in the ass.

[Neghae Mawla]
Sometimes that's hard to do, but I always try to keep them away from each other because inevitably, when you're doing the Fogarty, a lot of times, that clot will come and get stuck behind the sheaths or between the sheaths. Then I'm pulling the sheath back or pulling one of the sheaths out just so I can address the other one. Sometimes you get a lot of this little web of stuff that just slows the flow down. That's why I always try to make sure my sheaths are far enough away from each other. Typically, the places I will avoid are the cannulation zones, because I expect to find disease there or right around there. I try not to get near each anastomosis. I will stay proximal, but in the event that there's a juxta anastomotic stenosis or a swing segment stenosis, I try not to put my seven French sheath into any of that either.

[Chris Beck]
I think sometimes whenever you access too close into the juxta-arterial segment, where the vessel really narrows, then the sheath can become flow limiting…

[Neghae Mawla]
Yes, and so that's the problem. Then you got two sheaths that are touching and overlapping. Then it's just a hot mess.

[Chris Beck]
Can you talk a little bit about angioplasty of or near the arterial anastomosis? It's been my experience that sometimes this can be a very delicate area to work, and if you're overly aggressive, you can actually shut down or dissect. You can dissect inflow. You can cause a spasm. Can you talk about some technique things there or how careful you have to be if you're going to be working in that spot?

[Neghae Mawla]
I think the biggest issue there is really making sure you don't oversize it. I think if you're sized appropriately using whatever you want to do, if you've got the ultrasound, use the ultrasound and grab it. Size it according to the artery, and you should be fine. For the amount of pressure that you do, most of the time, I keep the arterial anastomosis around 10 or 12 atmospheres. I typically don't go higher than that. That's usually sufficient. I don't do long inflations. Most of my inflations, venous or arterial, are an up-down.

[Chris Beck]
I think that's something that can vary from operator to operator. If you're doing these a lot like an up-down technique, you realize it is totally sufficient for dialysis work. On the other hand, if you're someone who dabbles a lot in arterial revascularization, you think about these prolonged inflations and how you have to keep the catheter, or you have to keep the balloon up.

[Neghae Mawla]
I think I saw something several years ago that showed short inflation versus a three-minute inflation. I think the end conclusion was, "The final image looks good, but the reintervention rate was unchanged." … For dialysis access, these are big vessels. These are really mostly compliant vessels. All you gotta do is break the balloon open. Once it's open, I don't believe that you need to sit there and hold it open to change. I go up-down.

[Chris Beck]
There are a lot of anastomoses out there that I think you can spend a lot of time trying to get central, meaning that you cross the anastomosis, it's going distally easily, but it's not able to come up until the brachial artery. You're still able to get the same results just by pulling the Fogarty from the mid radial artery across the anastomosis.

[Neghae Mawla]
Usually, I'll go for the ulnar side, because the ulnar artery is a little bit bigger, but you don't have to get that far. Usually, if it's an upper arm, it's high enough away from the bifurcation. I like going up just because I think it saves me a little step down the line, but if it constantly keeps going distal down the forearm, then I say, "Okay, fine. Let's just do it that way." Do the Fogarty. I always use an over wire Fogarty.

Stenting vs. Drug Coated Balloons

For some resistant lesions, Dr. Mawla will consider placing a stent graft, either the Viabahn or the Covera. He does not use bare metal stents. Dr. Mawla will also sometimes use a drug-coated balloon (DCB) during a declot, particularly in lesions and in areas where cannulation occurs and it is hard to stent. For a resistant thrombus that is likely to cause repeat declot procedures, Dr. Mawla leans toward the DCB.

[Chris Beck]
Let's talk about lesions where you decide to stent. Taking extravasation off the table, which lesions and at what point do you decide to stent? When you are stenting, does it depend on location whether you're going to use bare metal versus stent graft?

[Neghae Mawla]
Always the stent graft. The data is there to show that the bare metal is just not that good. For me, it's always a stent graft, and I'm choosing between the Viabahn and the Covera. Usually, the costs are pretty comparable for me there. The Covera has a flared option, which I like, and so when you've got a graft, a seven millimeter that opens up into a 10 or 11 millimeter axillary, then the Covera there is actually what I prefer, because it opens up into that larger vein. But otherwise, I think the use of them are pretty much the same, but it really boils down to how resistant that lesion is. The other thing to keep in mind that's in the workflow now is the drug-coated balloons.

[Chris Beck]
Let's talk about the DCB's for the Dallas circuit. Do you use them during a declot, or do you declot and then bring them back if you have something that you want-

[Neghae Mawla]
No, if I want to do it, I'll use it during a declot. The problem with the DCB is that there's no reimbursement for it, but the advantages of both the Lutonix and the IN.PACT balloon is a 12-month guarantee that if I need to reintervene, they replace the balloon. It makes me feel better that, "All right, I've tried it, and it didn't work." No harm done that way. I think that actually is coming in before the stent graft. It's trying to figure out where that's going to fall into the algorithm, but I think normally I would say that falls into the algorithm before the stent graft does or should, particularly in lesions and in areas where we're cannulating and it's hard to stent. I don't like cannulating a stented region… I've seen too many stent fractures from that, so I try to avoid cannulating in the graft or in the fistula, where they're going to be using it. For there, I'll lean definitely towards the drug-coated balloon, but if I feel like it's resistant or going to come back, I will lean towards the DCB more on a repeat procedure than on a first procedure.

[Chris Beck]
Fair enough.

[Neghae Mawla]
Let's say I'm doing the declot, and it's their first time here, and I've got recoil like crazy. Then, stent graft can't be done because I'm afraid they're going to come back. Usually, let's say I've done it. I was happy with the outcome, but they come back two or three weeks, four weeks later. I will upsize it. Let's say they come back a third time within a month, because my final images look good, but they just are not holding. Then I'll say, "Okay, you know what? This is the scenario for a DCB."

Podcast Contributors

Dr. Neghae Mawla discusses Successful (and Quick!) Declots for AV Access on the BackTable 117 Podcast

Dr. Neghae Mawla

Dr. Neghae Mawla is an Interventional Nephrologist with Dallas Nephrology Associates in Texas.

Dr. Christopher Beck discusses Successful (and Quick!) Declots for AV Access on the BackTable 117 Podcast

Dr. Christopher Beck

Dr. Chris Beck is a practicing interventional radiologist with Regional Radiology Group in New Orleans.

Cite This Podcast

BackTable, LLC (Producer). (2021, March 22). Ep. 117 – Successful (and Quick!) Declots for AV Access [Audio podcast]. Retrieved from https://www.backtable.com

Disclaimer: The Materials available on BackTable.com 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.

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