Updated: Oct 21, 2020
Endovascular treatment of acute and chronic DVT has become increasingly more important to help prevent chronic post thrombotic syndrome. Vascular surgeons Dr. David Dexter and Dr. Steven Abramowitz discuss risks and benefits of different endovascular therapies, optimal procedure endpoint, and appropriate post procedure care. They also offer their thoughts on the Inari ClotTriever for treating DVT.
We’ve provided the highlight reel below, but you can listen to the full podcast here.
The BackTable Brief
Dr. Dexter characterizes the main types of endovascular DVT therapy: thrombolytics and pharmacomechanical treatment, aspiration, and mechanical thrombectomy. Acute clots are more amenable to aspiration, according to Dr. Dexter; chronic clots are more easily removed with mechanical thrombectomy, according to Dr. Abramowitz.
Both Dr. Abramowitz and Dr. Dexter note excellent thrombus resolution with the Inari ClotTriever, as well as the ability to evaluate clot morphology once the thrombus has been removed.
Thrombus removal may require the use of multiple devices and therapies. However, Dr. Dexter emphasizes the law of diminishing returns and potential damage with multiple catheter passes. <5% residual thrombus is optimal, according to Dr. Abramowitz.
Both Dr. Dexter and Dr. Abramowitz advocate for the use of sequential compression devices (SCDs) peri and post operatively to maintain blood flow and prevent stasis. They also emphasize follow-up imaging and anticoagulation maintenance in thrombectomy aftercare.
Image courtesy of Dr. Megan Chang, Interventional Radiologist at Baptist Health Medical Center in Little Rock, AR
Disclaimer: The opinions expressed by participants of the BackTable Podcast belong solely to the participants, and do not necessarily reflect the views of BackTable.
Determining the Best Treatment for Lower Extremity DVT
Dr. Dexter categorizes DVT therapy into thrombolytics and pharmacomechanical methods, aspiration alone, and pure mechanical treatment. Both Dr. Dexter and Dr. Abramowitz underline the importance in using the timeframe of the clot to help guide treatment. Aspiration is likely to be more effective for fresh clots, according to Dr. Dexter. Older, collagen-heavy clots are more easily removed with mechanical thrombectomy, according to Dr. Abramowitz.
Getting into some of the techniques—broadly speaking, how do you approach your patients in terms of trying to decide how you treat your typical patient?
I break DVT therapy down into three generalized buckets. Bucket A is thrombolytic or pharmacomechanical therapy where we're delivering a drug plus or minus a mechanical device to break it up. Bucket B is pure aspiration technology. Steven mentioned Penumbra already, and they're probably the biggest horse in the race for pure aspiration. Bucket C is purely mechanical, where we're not necessarily aspirating and we're going to eliminate the use of TPA to really get the clot out with some mechanical means. The risks of the procedure are also important to consider. Thrombolytic therapy has the bleed risks that makes some of us uncomfortable, but that's probably only true in frail patients, elderly patients, and recent surgery patients. In half of the patients that show up, I may be able to offer them thrombolytic therapy, and the other half, it's just sort of off the table. The next point is how fresh the clot is.
Yeah, I think the timeframe of the clot is really key. There are plenty of patients who come in with a delayed fragmentation. For patients who are coming in and who have a contraindication to lytic therapy, for the most part, the chronicity becomes a little bit important. There's that sort of collagen base layer that gets deposited in the clot or that transitions to the clot, starting around day four to five. Really once that collagen starts to organize a matrix within the clot burden, it becomes a lot more challenging to mobilize with a device that's purely suction based. That's where I start thinking about using something like the Inari ClotTriever or the Inari FlowTriever that gets in the IVC.
Unfortunately, as we've all said, DVT patients don't normally show up at day 1. They show up usually at the beginning of the second week, day 7, 8, 9, where they've been at home, taking some time off from work, elevating and compressing their leg. They just can't seem to get back to normal, and they've usually been on anticoagulation for that period of time because they were seen in the ER and put on a novel oral anticoagulant. The fresher the clot, the more likely I am to have aspiration work. If the ideal patient shows up to the hospital with clot that formed yesterday, aspiration may be very successful.
When to Utilize Mechanical Thrombectomy
For Dr. Dexter, mechanical thrombectomy is effective in lysing wall-adherent clots. Meanwhile, Dr. Abramowitz advocates for using tools, mechanical devices included, that will remove as much thrombus as possible. When lytic therapy fails or is not an option, mechanical thrombectomy can be a good option.
So, you put a thrombolytic catheter in, whether that's a standard thrombolytic catheter or an ultrasound enhanced thrombolytic catheter, and you go back the next day, in some cases, you get an amazing technical result. On venogram, on IVUS, the clot is gone. In some cases, you have residual clot. So, in those cases, the question is, what do you move on to next? I think that that's one of the areas where we say, "Well, maybe at this point, thrombolytic therapy has failed." Switching from thrombolytics to pharmacomechanical thrombolytics is probably not the right pivot for me. Now, you have all these dense pieces of fiber, and these tendrils stuck to venous wall. I need to find out some way to physically remove them from the wall. Five years ago, I think that was AngioJet and balloon angioplasty plus or minus a filter. Some of those pieces just kind of got mashed out of the way, some got morcellated, some embolized to a filter when one was placed. The addition of all these new mechanical devices has now allowed us to pull things off the wall.
You really want to make sure you have as little residual thrombus as possible. Really, I believe in using whatever tool is available to get as much of that thrombus out by intravascular ultrasound as possible.
I recently showed at the American Venous Forum our first 10 Inari clot favorite cases, which were not part of the trial or part of the registry. The majority of them were done for failure. They were done for failure of a different thrombectomy device. That's sort of when I started to make my change over from being a thrombolytic based interventionalist to a mechanical based interventionalist, where I was trying to leave the operating room with as much of an open lumen as I could, pulling out as much clot as I could. I really try to reserve thrombolytic therapy for those where I don't think that mechanical is going to give me adequate inflow, otherwise I move to mechanical pretty early.
Pros and Cons of the Inari ClotTriever
The Inari ClotTriever has expanded patient selection, allowing specialists to treat individuals with failure or contraindication to thrombolytic therapy. Both Dr. Abramowitz and Dr. Dexter note excellent thrombus resolution with the ClotTriever and discuss the satisfaction in being able to evaluate the clot morphology once the thrombus has been removed. For Dr. Abramowitz, the only con to using the Inari ClotTriever is potential numbness or paresthesia in patients post-procedure, although this is usually temporary.
I started using the Inari ClotTriever about a year and a half ago. It's a popliteal access sheath for me that has a nitinol basket that opens up inside the popliteal or femoral vein. We then put a large retrieving device inside this sheath and we're able to advance it past the thrombus. So, from the popliteal, we can get it all the way up to capture clot from the terminal IVC somewhere several centimeters below the renal veins usually and open a 16 millimeter coring element. Above this coring element is a basket that will collect whatever clot gets pulled off the wall and sort of funnels inside the basket. You pull it all down gently through until you reach your sheath. Once that's done, you can close your coring element down and pull the device out. In my practice, it takes me between four and nine passes to get a vein completely clean. At that point, the clot can be removed from the basket, set off to the back table, and you can look at the morphology of the clot.
Can you talk a little bit about the Inari ClotTriever and anything that you particularly like or dislike, any advantages or disadvantages to using this device?
I think there are a lot of pros. One thing I would say is expanded patient selection. Again, there's a very large oncology population that we were undertreating. They were given anticoagulation or a filter and sent on their way. So, the ability to treat people without thrombolytic therapy using these devices and getting a very good result with excellent thrombus resolution on IVUS has been great.
Tangibly identifying what we've taken out is probably the most satisfying part about removing clot mechanically. It's amazing seeing the different types of clots that we can pull out based on when patients had symptoms. You can really start to identify what's fresh clot, what's clot as it starts to organize a week to three weeks later, and what chronic things you can still remove after months of clot formation.
As far as cons, I've had a couple of patients who, due to the sheath size, I've seen some more neurologic complications. As a result of the sheath size and access in the popliteal vein, a few more patients were complaining of numbness or paresthesia down the back of the leg into the foot. But again, nothing that's been permanent, nothing that has made me question the device or question the access sheath size.
I'll say the biggest pro has nothing to do with the device but with the company. We don't have data on the vast majority of DVT devices and interventions that are used today. We try to do internal research and tracking… but Inari has made a dedicated effort to invest in researching the venous space, sometimes to their success and sometimes to their own detriment.
Determining Procedure Endpoint with Endovascular Treatment of DVT
Thrombus removal may require a variety of approaches and techniques. After using all possible devices without success, Dr. Abramowitz and Dr. Dexter both prefer to put the patient back on thrombolytic therapy with anticoagulation to re-assess. Dr. Dexter emphasizes the law of diminishing returns and potential damage with multiple passes and longer operating times. The goal is <5% residual thrombus, according to Dr. Abramowitz.
When do you consider a procedure over?
In an ideal world, it's when the clots are removed. I try to tell my residents and fellows less than 5% residual thrombus in the femoral-popliteal segment or the iliofemoral segment. Sometimes, no matter what you do, you're not going to achieve that goal. You could have used all devices at your disposal. In those cases, you can put the patient on Lovenox for three to four weeks. You can always bring them back, reimage, and you see how they're doing from a symptomatic standpoint.
This is one of those operations where tenacity is probably fairly important. Every day that you leave that clot behind, it just makes your job that much harder. So what do we do when we aren't done, when no matter what we've done, we still have a large burden of thrombus behind? I think Steven sort of alluded to it, which is anticoagulation, anticoagulation, anticoagulation. I would probably back out to thrombolytic therapy, park them for a day, come back, see what's chronic, and do everything in my power not to stent today, if I could help it.
To clarify, I'll tell you where the 5% came from…There’s a lot of emerging data and papers out there that have said, "The degree of thrombus that remains on that vein wall, even if it's 10%, 15%, 20% is associated with instant thrombosis." It's really challenging to treat that down the line and that's going to predispose our venous patients to recurrent DVT. Oftentimes, you'll run the IVUS catheter through the little cable segment and there’s that very, very thin line of residual thrombus in the vein, and people are like, "Oh, yeah, throw a stent in that.” That’s exactly what I don't think you want to throw a stent into. If you say like 10% or 15%, people see that rim layer left and they think it's okay to proceed. I like 5% because it usually triggers another level of concern for people of, "That's almost nothing." That's really what you want, like we're saying almost nothing.
The hard part is that the longer we're in there, the more likely we are to cause damage. Some of that damage is true and some of that damage is theoretical. Most of us cut our AngioJet time off at 300 seconds because at 300 seconds, we think the hemolysis risk probably outweighs the added benefit of further thrombectomy. With a Penumbra device, the more passes we make, the more blood loss there is. With a FlowTriever device, the more passes we make, the more blood loss there is. With a ClotTriever device, the more passes we make, the more likely we may be to have some intimal disruption. At some point, we all suffer from the law of diminishing returns.
After Procedure Care Following Lower Extremity DVT Therapy
Dr. Dexter and Dr. Abramowitz discuss follow-up care for thrombectomy patients. Both Dr. Dexter and Dr. Abramowitz agree on using sequential compression devices (SCDs) peri and post operatively to maintain blood flow and prevent stasis. They also emphasize follow-up imaging and anticoagulation maintenance.
Let's say you're finished with your patient, you've moved as much clot as humanly possible, you have good inflow, you have good outflow. What is your anti-coagulation protocol look like for these patients?
So, assuming a patient has come in on an anticoagulant that they seem to be happy with, and they're not failing, I want them on that therapeutic when they hit the door. I will question them in pre-op. If they've held it, I give them a dose of Lovenox before they get on the table. At the very least, I've got an oral Xa or an injectable XA therapeutic during the procedure. If they're on anticoagulant, I'll still bolus 5000 units of IV heparin, just to give something acute onset acting while I'm doing my work. If it's a terribly high-risk case, when they get off-table, I will give them another 5000 units of IV heparin. I typically just manage these patients post-op, whatever they were, on pre-op. I have not migrated my practice to three to four weeks of Lovenox, which I know a lot of people are doing right now. Anytime I see a failure, Lovenox is my go-to backup drug.
Anything with regards to activity or compression after the procedure?
I generally tend to leave the sheath in at the conclusion of the case, wrap the leg with a layer of Kerlix, and put a compressive sort of dressing right where the sheath is. I’ll remove the sheath, and I'll wrap a Coban all the way up the leg. At that point, if the patient's not ambulatory, I'll even put a sequential compression device (SCD) on, so that we get almost a simulation of that calf pump muscle moving right away. I want the people to be up and active as soon as possible. If not and they're still in the hospital or bedbound, then I'll keep an SCD on, just to keep the blood flowing through the recanalized venous segment. Again, it's that stasis that's going to cause recurrence of disease. Even if the patient is fully anticoagulated, the blood has nowhere to go and it's static. It's going to re-thrombose.
The addition of SCDs periprocedurally is incredibly important. We really don't know how well most of our anticoagulants are working throughout the patient’s stay in the hospital. So, for a difficult thrombectomy case, I will strap those SCDs the minute the popliteal sheath comes off in recovery and make sure they're running before I walk away from the patient. If your recovery unit doesn't have SCD machines and SCD sleeves, you need to get them. The utilization of SCDs has saved my tail more than once.
Once you finish the procedure, what's your typical follow up?
We use a fairly rigid follow up scheme. In the first year, they're seen at a month, 3 months, 6 months, and 12 months. At the second year, they're seen at 18 months and 24 months. And then from that point on, they're seen once a year. When I see them back at every one of those visits, I do a venous Duplex of the segments that I treated. In some cases, that's just an IVC Duplex and other that's an IVC Duplex and a lower extremity Duplex. If I am extremely worried, I’ll do a venogram and look with an IVUS. Very rarely do I add lab work on. Obviously, if someone's on Warfarin, they're going to get an INR.
The one thing I'll add is for patients who I perform deep venous stenting on, I will get some coaxial imaging at least once a year or an X-ray plain film if they don't want the CT scan. On that I'm looking for any stent deformation or change in the conformation of the stent, which would be indicative of scarring in the vein and a chance for failure. We're looking for thrombus that's relining the stents on that type of imaging as well. But I'll go back and emphasize, if you've done a good Villalta score or VCSS score, oftentimes, that's the first thing to change. In addition to that Duplex that you're getting into 3, 6, 9 months, if you're asking the patients how they feel symptomatically, you'll see that Villalta score start to change. Patients know their body, so they might say, "Hey, I'm really noticing that my skin's getting shinier or it looks a little redder and it's getting a little more woody.” They’ll come back in and they know that they have some recurrent disease.
Dr. David Dexter is a practicing vascular surgeon with Sentar Vascular Specialists in Virginia.
Dr. Steven Abramowitz is a practicing vascular surgeon at MedStar Georgetown University Hospital in Washington, D.C.
Host Dr. Christopher Beck is a practicing interventional radiologist with Regional Radiology Group in New Orleans, LA.
Cite this podcast:
BackTable, LLC (Producer). (2020, March 25). Ep 59 – Endovascular Treatment of DVT [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.
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