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BackTable / VI / Article
How to Declot AV Fistulas & Grafts Part 2: Finishing Touches & Follow-Up Care
Lauren Fang • May 1, 2021 • 928 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. In part 2 of this article, interventional nephrologist Dr. Neghae Mawla walks through the remaining steps of the declot procedure including arterial sheath placement (inflow), polish, closure, and follow-up. Dr. Mawla also addresses potential challenges such as recalcitrant stenosis and extravasation while offering troubleshooting tips and work-arounds.
We’ve provided the highlight reel in this article, but you can listen to the full podcast below.
The BackTable Brief
• After clearing clot burden and re-establishing venous outflow, Dr. Mawla addresses the inflow. He places a short, 6 Fr sheath directed toward the arterial inflow as well as a Kumpe and Glidewire across the anastomosis. Dr. Mawla does at least two passes with the Fogarty balloon across the arterial anastomosis to clear thrombus in the inflow. If Fogarty is not working, Dr. Mawla will perform an angioplasty with a 5 or 6 mm balloon at the arterial anastomosis. No thrombectomy devices are used in the arterial limb.
• During the polish stage, Dr. Mawla removes any residual pieces of clot burden by feeling for any resistance with the Fogarty at the venous anastomosis. If there is still significant resistance after several passes with the Fogarty, Dr. Mawla will consider upsizing the balloon, switching to a Conquest balloon, or stenting the outflow. While Dr. Mawla typically focuses his “polish” on the outflow, residual thrombus may also impede flow at the inflow, usually in patients with fistulas. Compared to the outflow and inflow steps, polish takes the longest amount of time to complete. In total, it takes Dr. Mawla 10 to 15 minutes to declot a graft and 15 to 20 minutes to declot an AV fistula.
• At the end of the declot procedure, Dr. Mawla gives another 5,000 of heparin. He uses StatSeal containing a hemostatic disc and applies pressure for several minutes to achieve declot closure and hemostasis. If Dr. Mawla is using anything larger than an 8 Fr sheath, he will use a purse string for closure.
• Dialysis providers are responsible for following patients post-declot. They perform surveillance with flow studies, physical exams, and symptom monitoring. For patients requiring repeat declot procedures--three to four thrombectomies a month--Dr. Mawla may consider putting in a catheter or referring for surgical revision. Typically, he does not prescribe anticoagulation for repeated thrombotic episodes.
• A common challenge during declot is recalcitrant stenosis in the venous outflow that does not efface with a standard balloon. If a standard balloon is not working, Dr. Mawla will switch to a Conquest balloon that is rated for up to 40 atm of pressure. With a tight waist, he may downsize the balloon. If a vessel is injured and active extravasation is identified, Dr. Mawla will quickly re-introduce the balloon across the injury, inflate, and hold for several minutes to tamponade. For a massive extravasation with associated hematoma, Dr. Mawla grabs a stent graft.
Table of Contents
(1) Back Bleeding and Arterial Sheath Placement
(2) Declot Polish
(3) Declot Closure
(4) Declot Follow-Up
(5) Challenges & Complications
Back Bleeding and Arterial Sheath Placement
After angioplasty, Dr. Mawla aspirates with a syringe from the venous outflow sheath to ensure he has cleared the clot burden. Then, he places the arterial sheath. Dr. Mawla pulls the Fogarty balloon across the arterial anastomosis, performing two passes. He may do several more passes with the Fogarty if unable to clear thrombus in the arterial inflow. If Fogarty is not working, Dr. Mawla will perform an angioplasty with a 5 or 6 mm balloon at the arterial anastomosis. No thrombectomy devices are used in the arterial limb.
[Neghae Mawla]
After I do the angioplasty, then I'll aspirate from that sheath, and then I can basically establish back bleeding. From my venous outflow, I've gotten the clot out, I may pick up a few bits and pieces of clot from the aspiration from that sheath at that point. It's all through a back bleeding process. Once I'm happy with that, I'll do a quick little injection to see what the outflow looks like. If that all looks good, then I'll put my second sheath in.
[Chris Beck]
What do you mean by the back bleeding technique and how are you aspirating from that venous sheath?
[Neghae Mawla]
Once your outflow is reestablished, and there's no significant clot burden, or even if there's a little bit, you're basically going to pull from your venous outflow. If it's an upper arm vein, let's say you're pulling from the axillary, then that will actually pull really well usually. I can usually just aspirate a syringe, maybe two syringes, just to make sure that it's clean, and so I feel like I've gotten the outflow completely cleared of any remaining clot.
[Chris Beck]
So then you go in with an arterial sheath. To recap, you did seven French for the venous outflow… you have a six French, a short sheath, directed towards the arterial inflow, and then it's another Kumpe and Glidewire across the anastomosis...
[Neghae Mawla]
Yep. That's basically it. The first time I'm doing everything, I will use a Kumpe to guide me. Once I know the patient's anatomy and what they're comfortable with, I'll usually just wire across. If I'm doing the outflow, I'll just take the balloon and do my central imaging with the balloon, and then I pull back with the balloon. Then I just angioplasty with the balloon, so I'm not having to swap out everything. The same thing on the arterial side. Most of the time, if the wire goes straight up into the artery, then I'll just go in with the Fogarty. I like having the wire proximal to the anastomosis in the artery, so into the brachial artery going up towards the axilla. That way, I can pull, and I can go back and inject. But if it doesn't work, and it goes down the arm towards the hand, I'm okay with that too, usually.
[Chris Beck]
Can you talk about the difference between having your wire in the brachial or having your wire go distal and why it matters for you for either a subsequent step?
[Neghae Mawla]
The next step is I’m going to pull with the Fogarty across the arterial anastomosis. I've got a syringe on each sheath. The one on the arterial sheath, the first, the seven French sheath towards the venous outflow, is just hooked up, and it's passive. My tech is aspirating on the venous sheath. That one is a little bit more active. I'll usually do two passes with the Fogarty balloon. The reason I have the syringe on the seven French sheath is because usually, once I clear to that level, that syringe will open up on its own, and so it gives me an indication that, "Okay, I've cleared up until this point.” But, if I'm unable to aspirate at the sheath where the Fogarty is in, then there's probably some clot right around there, but the other one will aspirate. Two passes there. If my wire's in the brachial artery, then I just take the Fogarty up into the brachial artery, and I do my injection. I just do an arteriogram. That's the only reason I really like having it up there if it goes up that way.
[Chris Beck]
Say it's the other situation where you're only able to get your wire to go distally, and then you've made your two Fogarty passes, do you then take a catheter and try and renegotiate that wire up into the brachia?
[Neghae Mawla]
Yes. At least what I will do is I'll just do a very slow injection through my sheath, and let it go retrograde, and I can get a little silhouette of what the arterial anastomosis anatomy looks like. I do it slowly. Just in case there's still a little bit of clot there, a little plug there that I haven't fully cleared, then I don't want to push that into the artery. I manipulate my Kumpe and my wire and steer and get up into the brachial artery.
[Chris Beck]
Whenever you're dealing with some clot that hasn't been cleared from your dialysis circuit, you don't want to blow in a whole bunch of contrast at the risk of blowing clot into the arterial into your inflow or outflow radial/ulnar artery.
[Neghae Mawla]
Right. That's why I do that part really slowly. If I do see some clot there, I'll do a couple more passes with the Fogarty, but most of the time, that clot is still there because there's probably a stenosis there as well. If I'm unable to clear the clot with the Fogarty, I will just do an angioplasty balloon.
[Chris Beck]
Which size? Do you start with a particular size, or do you have an injection that you're sizing to the stenosis?
[Neghae Mawla]
Either I'll do a five or a six millimeter at the arterial anastomosis.
[Chris Beck]
Are there any particular balloons that you like for declots, or you'll just take anything?
[Neghae Mawla]
I just take anything. Our standard balloon is the gladiator, which I think is the Mustang in the hospital. That's my standard go-to balloon for everything. I will use a conquest if I don't get full effacement with that balloon. Then at the arterial side, I will use the Ultraverse if it's a very tight band, because sometimes, that Gladiator doesn't want to make that U turn up. The Ultraverse has been really nice for that. Everything I do is over a .035”. I think once a year, I may grab an .018” balloon system just to make that bend into the artery into a radial artery that the .035” system wasn't doing, but everything is .035”.
[Chris Beck]
At this point, you've tuned up the arterial anastomosis or the juxta-arterial segment. Do you ever, at any point, use any devices in the arterial limb or across the anastomosis?
[Neghae Mawla]
No. I've never done that. I'll get close. If there's an aneurysm or an aneurysmal segment in that juxta anastomotic region, I'll put the device into there, but I'm very particular about not crossing the device into the artery.
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Declot Polish
During the polish stage, residual pieces of clot burden are removed using a rotational thrombectomy device or a Fogarty balloon. Most of the time, Dr. Mawla feels for any recoil with the Fogarty. If it crosses the venous anastomosis with difficulty or with significant resistance, Dr. Mawla will consider upsizing the balloon, Conquesting the balloon, or stenting the outflow. Residual thrombus may also impede flow at the inflow, usually in patients with fistulas. Polish takes the longest amount of time compared to the inflow and outflow steps of the procedure. Overall, it takes Dr. Mawla 10 to 15 minutes to declot a graft and 15 to 20 minutes to declot an AV fistula.
[Chris Beck]
All right, so you've treated the venous side. Now you've treated the arterial side. What's next?
[Neghae Mawla]
This is that polish stage. If there's a little recoil, if there's a little extra clot burden, maybe go after it with the cleaner or the balloon or the Fogarty. Just polish up what the outflow looks like. Then you're pretty much done. If there's a central lesion, now's the time to go assess the central again, and see if I decide this to be a clinically important central lesion that I want to balloon. I have had the scenario where patients did not have arm swelling before the declot, and then I see something centrally during the declot.
[Chris Beck]
Talking about the last section of the procedure, basically, what you're calling the polish portion, what is your endpoint? Are you trying to evacuate every piece of clot that you see? I know it's hard to quantify, but how much clot burden are you comfortable with at the end, and does it change whether you have a fistula that you're declotting versus a graft that you're declotting?
[Neghae Mawla]
For a graft, no. Most of the time, it depends on where it is, but if it hangs out at the venous anastomosis, I might think that there's residual or recoil that's there. A lot of times, what I'll do is I'll take my Fogarty, and just use it as a diagnostic feel. If you inflate the Fogarty and go forward, if it crosses the venous anastomosis without any difficulty, and you're not getting a lot of resistance, I'll usually just say, "Okay, we're happy. We're good." But if I'm getting resistance pushing that Fogarty, then I'll say, "You know what? There's probably some recoil here that maybe it doesn't look as bad on imaging." That's when you want to say, "Okay, do I want to come back and upsize the balloon, conquest the balloon, stent the outflow?" If you think about how much clot is in a dialysis circuit, you're looking at five mls, maybe seven mls. It's not a lot of clot burden in there. To say that I'm leaving a little bit behind, I mean, how much am I leaving behind?
[Chris Beck]
I've run across different people with different schools of thought. Some people believe that it's sacrilege to leave any amount of clot in grafts because they think that that clot is thrombogenic. If you leave anything in the circuit, that clot then seeds the rest of the clot, and it creates a clot bomb. Then I've seen some people who are just more forgiving of the fistula. They say, "It's an aneurysm segment. It's sometimes difficult to clean out the whole thing."
[Neghae Mawla]
I go a lot by exam here, because if I've got a good thrill, and it's not pulsatile and I don't feel that resistant pulsatile outflow, then I say, "You know what? This is probably not a hemodynamically significant residual clot." Large ones are hard to open up, and there's actually a handful of nephrologists that will do a mini open thrombectomy, where they'll just make a little cut down into that aneurysm, squeeze it all out, and then close it off. They will basically put a balloon on each end, and so they've got hemostasis and control, proximal and distal controls. They'll put a Fogarty up. They'll put a balloon up, and then you can cut down to the aneurysm, express out all the clot, close that up, and then continue on with your percutaneous side of it. That's a really fascinating technique. The ones that I struggle with are the big aneurysms, and making sure I've got adequate clearance of all that. That's why I like the cleaner 15 for that. That's why I'll use TPA there. The other one I'll struggle with is a patient that had a, for example, brachiocephalic fistula that then got converted into a graft, and the surgeon has decided to anastomose the PTFE to the original AV fistula as opposed to making a new or true arterial anastomosis. You've got this dilated vein stump between the artery and the PTFE, and a lot of times, the graft segment opens up really easy. The outflow is easy. It's that little segment that I sit there, and I spend a lot of time on, and that may be an additional 10, 15, 20 minutes just working on that little segment.
[Chris Beck]
What is your average time in starting and ending a declot? How long does it take you?
[Neghae Mawla]
I think average is probably between 10 to 15 minutes, for a graft. Fistulas take a little bit longer, sometimes a little more unexpected, so 15 to 20 for a fistula… If I'm pushing 20 minutes, it's because there is one residual. It's usually in the polish stage, where it's just this one little piece that I feel like I need to get either in the inflow or less often in the outflow. In the outflow, if I get annoyed, I'll just put a stent graft across it, and I'm done. But a lot of times, it's just one little clot in the inflow that I think is still impeding flow that I just have to address over and over again. Most of my time is spent in the polishing stage. The outflow is a couple of minutes. The inflow is a couple of minutes, and then it's just a matter of getting flow established adequately and comfortably.
Declot Closure
At the end of the declot, Dr. Mawla administers another 5,000 of heparin. He pulls the sheaths out and uses StatSeal with a hemostatic disc for closure, giving approximately five minutes of pressure with that when using six, seven and eight French sheaths. If Dr. Mawla is using anything larger than an eight French, he will use a purse string for closure.
[Chris Beck]
The only anticoagulation you give is the 5,000 of heparin in the beginning. Your procedure's pretty quick. I assume you're not doing intermittent heparin.
[Neghae Mawla]
No, I always do a little heparin at the end. I give another 5,000 at the end, so the total will be 10,000.
[Chris Beck]
Then what do you do for either closure or hemostasis once you're all finished?
[Neghae Mawla]
Oh, we just take the sheaths out and pull. I use the StatSeal, which has the hemostatic disc, and so usually about five minutes of pressure with that. I'll use that for six, seven and eight French sheaths. If I'm going bigger than an eight French, I'll put a purse string around it and send them home with that, but otherwise, I do the StatSeal. That way, it's just the disc and a dressing over it, and they take it off the next day, and there's no more sutures to worry about. Put the StatSeal, manual hemostasis. They're in recovery 30 minutes, and they're out the door.
Declot Follow-Up
Post-declot, patients are followed by their dialysis providers, who will perform surveillance with flow studies. Sometimes, patients will require recurrent declot procedures. However, if a patient is receiving three or four thrombectomies a month, Dr. Mawla may consider putting in a catheter or referring for surgical revision. Typically, he does not prescribe any anticoagulants only for repeated thrombotic episodes.
[Chris Beck]
In terms of the follow-up... Is it up to the dialysis clinics to be doing some basic surveillance on these patients either with recirculation, or they're doing physical exams? How do people get fed back into you so you avoid the declot, and you catch them with some fistulogram maintenance when you're just tuning up?
[Neghae Mawla]
That's at the dialysis level, so they're doing surveillance with flow studies. There's a couple of different devices to measure flow studies out there that each dialysis provider has. They do physical examination. They do symptoms. Patients say, "I'm bleeding too long after dialysis. It can't stop," so they know to come back. The dialysis clinic and the patients are usually the ones that are responsible. Depending on the disease severity, I might say, "Come back. Let me just do a physical exam myself." I may bring them back just for a physical examination after a month, after a declot just to say, "Let me take a look and see what it feels like, and make sure that it's not acting up again." But most of the time, I leave it up to the dialysis center.
[Chris Beck]
Let me ask you a specific scenario that may or may not come up in your practice. But say you're seeing someone on a semi regular basis like every month, or you can even take it down to every week or two weeks where you're having to do a declot, at what point do you say, "This isn't working. Let's have this either surgically revised or put in a catheter," or what do you do with that scenario where you feel like you're having to see that patient over and over for declot?
[Neghae Mawla]
That's always the tricky one, right? That's the one we don't like talking about. Usually, at that point, I'm coordinating with the surgeons and saying, "All right, I've done this guy three times this month. What's our next plan of action? I think the issue is this." If it's an outflow one that I can stand, I will do that. If it's an inflow that I think I need patched, then I coordinate with the surgeon, and I say, "All right, how are we going to do this? Are we going to do this now, next week, or should I put in the catheter and let you deal with it?" Usually, if I can coordinate something pretty quick like in the next week or so, and I think that they're holding open for that week, then I'll go ahead and just do the declot again. I'll say, "Okay, fine, let me open you up," and then let him revise you as an outpatient. They'll just schedule them straight to the OR. That's usually when I'm calling the surgeon and say, "All right, don't see this guy in the office. Just let me declot him. You take him to the OR. Patch the arterial anastomosis, and we're good." It's the ones where we don't know what's happening that we struggle where we start adding in Plavix and Eliquis… Typically, I don't put anybody on any coagulation only for repeated thrombotic episodes. Generally, three or four thrombectomies inside of a month, that's when I may say, "You know what? Either this one is done, and we've just been trying to salvage it, and then put in a catheter or it's a specific focal lesion every time that isn't holding, and I want a surgical revision of that or it's the venous outflow that I just need a bypass segment of that.” If it's something that looks like a relatively easy surgical fix, where I anticipate, "Hey, if you just do this little bit and we should be fine, then I'll declot him again, and let the surgeon do their picks." But if it's failing, it's a five years old, seven years old kind of thing, then at that point, I say, "Look, it's done. Let's just put it in a catheter and go."
Challenges & Complications
For recalcitrant stenosis that doesn’t efface with a standard balloon, Dr. Mawla will switch to a Conquest that goes up to 40 atm of pressure. With a tight waist, he may downsize as well to avoid extravasation. If a vessel is injured and extravasation is seen on the post run, he’ll run the balloon back up and hold for several minutes to tamponade. For a massive extrav where a hematoma is forming in the arm, Dr. Mawla grabs a stent graft. If you are in a situation where you don’t have balloon access because it is off the table for example, Dr. Mawla recommends putting a thumb on the graft right behind the sheath to control the inflow and prevent bleeding.
[Chris Beck]
One of the things that I wanted to get into, the troubleshooting component, that I think can hang people up is if you have a recalcitrant stenosis. If a stenosis doesn't efface with the Mustang, you mentioned that you would go to another balloon. Would you talk a little bit about that, and why you go to that balloon?
[Neghae Mawla]
Usually, I'll go to a Conquest. My Conquest goes to 40. I usually have a 30 also, I think, but I have the Conquest 40. I can go up to 40 atmospheres there. Usually, I'll keep that at the same size. Sometimes if that waist is really tight, I may actually downsize my Conquest first just to avoid the extravasation, because let's say it's a seven millimeter balloon, and it's still at 25 or 30 atmospheres because I'll push these balloons. I'll get up to 25 comfortably and sometimes even 30. Let's say I still look like what I think is a 50% waist, then I may grab a six millimeter Conquest, get that fully effaced and then come back with my seven millimeter again. It's probably just as safe to grab a seven Conquest and just do it. I just feel like sometimes, you want to be cautious and you think, "I'm being much more cautious if I grab a six versus a seven." The reality is it probably doesn't make any difference, but it makes us feel better.
[Chris Beck]
What happens if you do injure the vessel? It's a venous outflow stenosis. You do your post run, and you see some extrav. Will you talk about your protocols, how you work through that?
[Neghae Mawla]
Then I will just take the balloon up there, and I'll hold it for three minutes or so, and just do another run and see. Most of the time, that takes care of it. If I have a massive extrav and a very large one, especially something that I can see a hematoma forming in the arm, I'll grab a stent graft. But most of the time, it's small enough that if you just hold the balloon up there, it'll tamponade off on its own. You're just holding pressure. Whether you do it from the outside or inside, it doesn't matter.
[Chris Beck]
That's also been my experience. It's funny that we did a lot of these in fellowship, and I don't remember ever rupturing a fistula or a graft, and then it happened to me twice in my first year. They tell you the trick. I'll say another thing that I do is whenever I pull a balloon out to do a run, I always keep the balloon on the wire very close to the sheath. I mean, that was something that was drilled into me. My techs are always very quick. They want to get that balloon off, but I just hold it right there near the sheath. That way, you're always in a position to run that balloon right off and tamponade something.
[Neghae Mawla]
The balloon, just pull it off to the side of the sheath, and you're done. I will say for this tamponading, it's usually six atmospheres, eight atmospheres just to get the minimum pressure.
[Aaron Fritts]
Chris, that was the first dialysis case I did with Peter Bream that he drilled that into me. Always keep your balloon right here just in case. You know why? Because that first case, it ruptured, and we threw the balloon right back in and blew it up.
[Neghae Mawla]
The other thing you can do in case you don't have balloon access and if it is off the table, and you're waiting, you just put your thumb on the graft right behind that sheath. Just control the inflow, and then it's not going to bleed either. There's lots of ways to do it. I think the easiest way is just take the balloon in there and go... There have been a few instances where I have lost wire access, and I'm trying to get the wire back across. At that point, I will get my Fogarty back into the proximal graft, and I'll do proximal control with the Fogarty. Then that way, I'm not flowing out while I'm trying to wire back across the outflow, so I've got time to get my wire back across the outflow. Most of the time, I do it with a single wire. I'll pull the wire. I'll pull the vents in, and then I'll go on the arterial side and pull the vents. If it was something really tight where I say, "You know what? I don't want to lose this wire or lesion that was really difficult to cross. I spent a couple minutes trying to cross that,” then I won't do that again. I'll leave the wire. But, if the wire goes up very quickly and easily, and the outflow opens up the way I expect, then I just pull that wire, and I use it on the arterial side also… Usually, once I've done the Fogarty and I'm happy with my inflow, I never go back to it. I usually would go back to the outflow and readdress the outflow, but I never go back to the inflow.
Podcast Contributors
Dr. Neghae Mawla
Dr. Neghae Mawla is an Interventional Nephrologist with Dallas Nephrology Associates in Texas.
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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