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How to Declot AV Fistulas & Grafts Part 1: Patient Prep, Access, Outflow

Author Lauren Fang covers How to Declot AV Fistulas & Grafts Part 1: Patient Prep, Access, Outflow on BackTable VI

Lauren Fang • Apr 24, 2021 • 1.1k hits

Arteriovenous fistulas and grafts are dialysis access sites that can thrombose, as we well know. 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 1 of this article, interventional nephrologist Dr. Neghae Mawla walks through the initial steps of the declot procedure including pre-op workup, obtaining access, and treating outflow lesions.

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

The BackTable Brief

• Dr. Mawla’s pre-op evaluation is quick and entails a physical exam of the graft/fistula and overlying skin. A declot procedure may be postponed if a patient is fluid overloaded and cannot lie flat on the table.

• Patients undergoing a declot procedure are administered moderate sedation--fentanyl or versed.

• To obtain venous access, Dr. Mawla uses Merit’s seven French sheath with a microwire and an access needle. Dr. Mawla uses palpation instead of ultrasound guidance for access. The patient receives 5,000 of heparin. After the central run, Dr. Mawla performs a pullback venogram, examining the outflow veins to visualize the clot burden and potential stenosis.

• Many operators will administer thrombolytics such as TPA to treat clot burden in the outflow. However, TPA is not part of Dr. Mawla’s standard procedure, as he prefers to use balloon maceration or a rotational thrombectomy device followed by angioplasty. For highly resistant clots or during instances of large aneurysm burden, Dr. Mawla may administer 2 mg of TPA, but this is rare. His go-to devices are the Argon Cleaner (6 Fr XT and 7 Fr 15) and Mermaid Medical’s D-Clot Device.

• Dr. Mawla’s declot steps are outflow, inflow, and polish. However, some operators choose to place an arterial sheath to address the inflow first.

Loop graft with arterial and venous directed sheaths for declot procedure

Table of Contents

(1) Declot Patient Pre-op Workup & Room Setup

(2) Declot Access & Examining Outflow

(3) Treating Outflow

Declot Patient Pre-op Workup & Room Setup

For Dr. Mawla, a declot pre-op workup involves a quick physical exam to evaluate the skin. If a patient is fluid overloaded and cannot lie flat on the table, he will postpone the declot. Otherwise, Dr. Mawla will proceed with local and moderate sedation, typically fentanyl or versed. As far as room setup, Dr. Mawla likes to stand where the armpit is for a left arm and at the head of the patient for a right arm. This way, his right hand is doing most of the work, driving centrally. A movable C-arm keeps his table centered and fixed.

[Neghae Mawla]
I'm an interventional nephrologist out of Dallas. I work in an ASC setting. All I do is interventional work, and so it's dialysis access maintenance. We do about 2,500 cases a year at our center, about 50 declots a month on average. We've streamlined the efficiency.

[Chris Beck]
When patients come to you, and it's a declot procedure, you know it's a declot, what does your workup look like beforehand in the center? Do you do anything ahead of time as far as physical exam or ultrasound evaluation?

[Neghae Mawla]
I don't do an ultrasound evaluation. I just do a quick physical exam, usually just looking at the skin. I make sure there's nothing there, try to assess for aneurysm sizes that may be complicated along the way. But assuming it's a standard PTFE graft, either straight in the upper arm or loop in the forearm, it’s really just trying to figure out where the arterial side is. Every now and then, I have a patient that can't tell me which one's their arterial side. I always like to get my venous access in first. That's the only reason it matters, but it's not a deal breaker if I can't figure it out. I've always been a two sheath kind of guy. I know there's a couple of people that do a single sheath thrombectomy. I just don't like flipping back and forth if I need to, so I've always done the two sheaths anyway. Really, that's the only thing I'm trying to figure out and then other basic things like when was the last time you had an intervention? If you're at our center before, I usually go back and review previous films. The pre-op visit is pretty quick.

[Chris Beck]
Is there anyone that you will not perform a declot on in terms of either they just recently had their graft or fistula placed or someone's potassium hits a certain level where you won't go after a declot? Is there ever a situation where you place the catheter, get dialysis, then bring them back after things have settled down?

[Neghae Mawla]
I don't have access to labs. I don't worry about potassium. I never worry about INR or platelet counts or anything like that. We just go as far as it's quicker to put a catheter in. I mean, the ultimate answer is I gotta get them dialyzed, and so whatever is quicker to dialyze. Most of the time, I can do the declot just as quickly as I can do the catheter. Again, dialysis is not always accessible for them. Most of the time, they leave me, and they go back to their home facility to get their dialysis treatment. I don't do the catheter then. The only time would be if they say they absolutely cannot lie flat on the table because they're just so overloaded, that I would say, "Okay, fine, maybe I can keep them propped up, do a quick femoral catheter, get them dialysis and bring them back in a couple of days and do the declot.”

[Chris Beck]
As far as anesthesia requirements for the procedure, are you doing local, moderate sedation, something deeper?

[Neghae Mawla]
No, just moderate sedation and local, [fentanyl and versed].

[Chris Beck]
All right, so the patient makes it out of the preoperative area, and they're on the table for you. What are some of the things that you're considering as far as room setup? One of the things that I feel like sometimes I struggled with, especially early on, was making sure that my techs had the area prepped appropriately and had enough access where you're not just putting one sheath in. I'm also a two sheaths kind of guy, so sometimes they have to prep a little higher up than they think, but can you talk about room setup? Things that you have prepped and ready to go to create those efficiencies for the procedure?

[Neghae Mawla]
Usually, my setup is pretty standard across all of my cases, whether it's an angiogram or a declot, and so the room setup is pretty straightforward. I typically like to stand where the armpit is with the arms extended out. I'll stand to where the armpit is for a left arm, and I'll stand at the head of the patient for a right arm. I just stand opposite. That way, basically, my right hand is doing most of the work driving centrally.

[Chris Beck]
Do you have a fixed system? Is it like a movable C-arm? That's one of the things you hear a lot--complaints about if you have a fixed system, the declot can become a little bit cumbersome because you're either having to break the table or you always feel like you're in the way as the operator.

[Neghae Mawla]
I have a movable C-arm. That way, my table is pretty much centered and fixed, and all of the movement is with the II. That makes it much easier. My monitors are mounted on the ceiling, so they're easy to swing around to whatever position I need to.

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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Declot Access & Examining Outflow

Dr. Mawla obtains venous access using Merit’s seven French sheath with a micro wire and a micro access needle. This is done through palpation. The patient is put under conscious sedation and given 5,000 of heparin. If a central stenosis is identified after the central run, Dr. Mawla reserves this for the end and will proceed with the declot. After the central run, Dr. Mawla does a pullback with contrast, examining the outflow veins to identify how much clot burden is present. He stops the pullback once the thrombus has been located.

[Chris Beck]
All right, so you're starting the procedure. Any preoperative medications? Do you give heparin? What's the first thing you do?

[Neghae Mawla]
I don't do an IV in preop, because these patients, it's just so hard to get sometimes. I'm going to be in there anyway. I do all the sedation and medications myself, so we don't have separate IV access for any rare cases. First, in the arterial limb, let's say it's closer to the arterial anastomosis, I'll put my seven French sheath in directed towards the outflow, and then usually a Kumpe catheter straight up into the central veins. I do my central run, conscious sedation, 5,000 of heparin. That's how I start.

[Chris Beck]
Whenever you're getting access, just by palpation, do you like ultrasound guidance?

[Neghae Mawla]
I do it just by feel because I've just always done it that way. Merit has a seven French with a micro wire and a micro access needle, and so that's the kit that I use. It's a short four-centimeter sheath. One of my pet peeves is when my sheaths are overlapping, so I keep it with a four-centimeter sheath for my declot, and I just do it by palpation. If it's somebody that is a fistula that is difficult to palpate, then I'll bring in the ultrasound, and do it under ultrasound guidance. But let's say a PTFE or a very well established fistula, I'll just go in by feel.

[Chris Beck]
Gotcha. All right, so you do your central run. Let's say you do have a central stenosis. Do you go ahead and treat that right after you've done your central run, or do you reserve that for later?

[Neghae Mawla]
I reserve that for the end, assuming there's no thrombus burden all the way up to the centrals, but I would say it's there, but it's not the reason for the thrombotic episode. That's why I say I reserve that for the end. Let me just go do the declot first. Then it's basically looking at a central angiogram and angioplasty at that point.

[Chris Beck]
You have your seven French in. You've done your central run, looks clear centrally. At that point, are you getting arterial access?

[Neghae Mawla]
No, so then I'll do a pullback with contrast. I'll just look at the outflow veins to identify the level of the stenosis. With your graft, it's usually at the venous anastomosis. We look at the outflow vein and how much clot burden there is in the outflow vein. Most of the time, it's not that much. It's all in the graft. Once I identify that and I see my thrombus, I stop with my pullback. I'll take the Kumpe out. The way I was always taught was outflow, inflow, polish.

[Chris Beck]
That's a good summary of the procedure.

[Neghae Mawla]
I mean, if you can do that, then you're good. My partner used to always do inflow. He would get up to this point, do the central, sedate, pullback, and then he would get his arterial sheath and then do the inflow. That works, too...But I was always taught if there's no outflow and you can't get an outflow, why did you bother with the inflow?

Treating Outflow

There are many ways to treat clot burden in the outflow including straight balloon maceration or rotational thrombectomy device followed by angioplasty. To determine which of these methods to use, Dr. Mawla considers length of circuit, clot burden, age of graft, and the possibility of multiple disease points along the circuit. The longer the circuit or the bigger the clot burden, the more likely Dr. Mawla is to grab a device, either Mermaid Medical’s D-Clot or the Argon Cleaner. With older grafts and patients who have multiple disease points, Dr. Mawla opts for ballooning so that he can macerate and treat at the same time. A standard thrombectomy for Dr. Mawla does not include TPA unless there is resistant clot or a large aneurysm burden.

[Chris Beck]
How do you treat the outflow? Is it a combination of Fogarty? Do you use any thrombectomy devices, either aspiration or mechanical?

[Neghae Mawla]
This is where it gets fun, and this is where everybody...

[Chris Beck]
...has their own signature.

[Neghae Mawla]
Exactly. There's a couple of ways of doing it. There's really two ways that I do it. One is balloon maceration. I'll take a seven by eight centimeter balloon, and I'll just balloon from lesion all the way back to the sheath. Or, I will do a rotational thrombectomy device. Which one I decide varies based off of two factors. One is how much length of the circuit there is. The longer the circuit or the bigger the clot burden, the more likely I am to grab a device as opposed to just balloon. If it's an older graft, and there's a lot of age and I know their history, not only is the venous anastomosis going to be a problem but also their venous cannulation side, their arterial cannulation side. If I'm expecting and I know multiple disease points along the way, then I'll just balloon it at that point, because then you can macerate and treat it all at the same time.

[Chris Beck]
Gotcha. As far as devices, do you have a preferred device if you are going to go to the device route?

[Neghae Mawla]
I have three devices. I have an over the wire trerotola. The only reason I don't use it very often is because of cost. For an ASC, it's the most expensive having that over the wire device. But on that rare occasion, where I feel like I don't want to lose my wire, just because for whatever reason it took so long to get across the venous anastomosis that I just don't want to lose it, I'll grab that. Then I have the Argon cleaner thrombectomy device. There's actually two sizes. There's a six French XT, and there's a seven French 15 that has a larger diameter. Then, I have the D-Clot thrombectomy device by Mermaid Medical, which is also a rotational thrombectomy device. Actually, I have four because I have two different Argons.

[Chris Beck]
Putting the trerotola aside where you're trying to maintain your wire access, how do you decide between whether or not you're going to go either your seven or six French Argon cleaner?

[Neghae Mawla]
Between the six and the seven French Argon is based off the size. If I've got a big fistula with a large pseudoaneurysm, then I will grab the seven French usually. The cleaner XT, I think the maximum diameter is 10 maybe 11 millimeters versus the 15, that's a 15 millimeter diameter, so it's a stronger battery and rotational force. For a larger and reasonable fistula, I'll grab the 15 first.

[Chris Beck]
It seems like you're either going balloon macerate or device. Is there any situation where you just go Fogarty and just push the clot with a little Fogarty balloon or?

[Neghae Mawla]
If it's a brand new graft, and I expect everything to be healthy, then sometimes I'll do just the Fogarty on the arterial side. I'll put the sheath for the arterial side very close to the venous anastomosis. If it's three, four weeks old and declotted off, then a lot of times, you can start with that. I just get a lot of clot clearance that way, and I'm not expecting anything else. Sometimes it's just easier to do the Fogarty that way.

[Chris Beck]
If you do decide to go with a device like the cleaner, are you using any thrombolytics with that? I mean, I know that you had already said that you do the heparin after you do your central run, but any TPA?

[Neghae Mawla]
I don't use TPA as a norm. It's not my standard. I'll use it when I'm stuck, when I'm seeing resistant clot, or if I've got a large aneurysm burden. Also, I may take one of my Kumpes in there. In the early step, I may drop a little bit, usually two milligrams of TPA, but TPA is not a standard step inside my thrombectomy. Usually, what I do is when I grab my device, either the cleaner or the D-Clot, if it's a standard graft, I alternate back and forth. Sometimes I feel like a cleaner. Sometimes I feel like a D-Clot. I basically will just turn it on, and I'll pull, and then through the side port [of the device], I will just slowly inject a little bit of contrast. That way, I can see if there's macerated thrombus burden as I'm doing the pullback. I even use 10 CCs of contrast, usually, to inject, and I can see what my outflow looks like and where all my lesions are. The other thing I like about these devices is you will actually see the tip or the rotational component getting narrower as you come across a stenotic lesion, and so even without a contrast injection, you can usually identify, if you're following it, where you're going to come across a lesion along the way.

[Aaron Fritts]
...Do you find that the devices help decrease procedure time? Are you just balancing that with the cost in terms of your decision to use a device?

[Neghae Mawla]
It usually does decrease the procedure time, and it depends on the length and the disease circuit. If I've got a loop graft that's stented all the way up to the axilla, it's just going to be faster for me to grab the device and just pull that all the way through the outflow. That way, I just go balloon in one location of the two locations that I see, as opposed to going and ballooning the entire different segment. I think that's a little bit faster. I think I get a little bit better clearance of thrombus burden using the device than using the balloon… I don't know that there's actually any data that suggests that one is actually better than the other as far as balloon versus these rotational devices or catheter aspiration. For me, it's a matter of what I think is going to be faster and a little bit safer. Patients that have a large clot burden, I tend to reach the device first.

[Chris Beck]
All right, so you handled the outflow with either a balloon maceration or thrombectomy, and you feel pretty good that you've macerated the clot burden. What do you move to next?

[Neghae Mawla]
If I'm doing balloon maceration, angioplasty is all done in one step. If I'm doing the device, then I'll go to my angioplasty of the outflow. I usually start with a seven millimeter balloon as my standard for anything and everybody, unless it's a really small fistula or something I worry about. But, usually a graft, I'll start with a seven millimeter balloon. Most of our grafts here in the Dallas area are the tapered four to seven, and so most of the venous outflow is a seven. But even if you don't know, you're safe to upsize by one usually. That's why I say even if it's a six millimeter straight graft, a seven millimeter balloon is going to be fine. That's why I always start with the seven.

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

Disclaimer: The Materials available on 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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