Anticoagulation Strategies Before and After Endovascular Procedures
In this podcast, Afshin Assadian, MD, highlights his session at the VEITHsymposium 2021, during which he spoke about safe anticoagulation prescribing for patients undergoing fenestrated-branched endovascular aortic repair (E/B/EVAR) who require spinal fluid drainage.
- Assadian A. Safe anticoagulation in F/B/EVAR patients requiring spinal fluid drainage. Paper presented at: VEITHsymposium 2021; November 16-20, 2021; Virtual. https://www.veithsymposium.org/index.php?pg=program-2021
Afshin Assadian, MD, is a vascular surgeon and the Head of the Department of Vascular and Endovascular Surgery at Klinik Ottakring in Vienna, Austria.
Amanda Balbi: Hello everyone, and welcome to another installment of Podcasts360. I’m your moderator, Amanda Balbi with Consultant360.
The VEITHsymposium took place from November 16 to 20 this year and included various educational sessions. One such session titled, “Safe Anticoagulation In F/B/EVAR Patients Requiring Spinal Fluid Drainage,” was presented by Dr Afshin Assadian, who is a vascular surgeon and the Head of the Department of Vascular and Endovascular Surgery at Klinik Ottakring in Vienna, Austria. He joins us today to shed light on his session.
To begin, can you give us a brief overview of your session and the research you presented?
Afshin Assadian: So, I'll just give you some brief ideas about the background of what the therapy means and what the complications of the therapy could mean. During thoracic-abdominal repair of the aorta—this is the largest vessel in the human body—we're treating enlargements of the aorta, which can rupture, and they inevitably cause death in patients. In therapy, we are talking about in our endovascular therapy group, line the aorta from the inside and exclude the enlarged artery, so that there is no further pressure on the artery, and it cannot rupture.
There are a couple of complications going with it, and one of the worst complications of disease is that, due to the coverage of the aorta, you can also cover the arteries that do fuse the spinal cord. So, if you cover those and the spinal cord doesn't get enough blood, you can end up with paraplegia, which is terrible for quality of life. There are a couple of strategies that aim to prevent spinal cord ischemias. This is one of the worst complications, but this is one of many complications.
Another complication is that these will connect big branches, which take off the aorta, like the renal arteries or the arteries that fuse the gut, the pancreas, the liver. We will connect those with little stents to the big stent so that they are still profused. The problem of these connections is that they need some anticoagulation in order to stay patent so that the blood flow is continued and there is no closure.
Actually being able to guarantee that, you have to be quite aggressive in blood thinning measures. You will have to give different blood thinners—heparin or drugs that are focused on platelet activation like aspirin, for instance. The problem is that these medications can produce complications with one of the most important measures: preventing spinal cord ischemia.
This measure is a catheter, which is placed in the spinal area. If the pressure of the fluid in which the spinal cord is swimming—If this pressure is going up, we will drain the fluid and decrease the pressure. By doing so you will increase the blood flow in the spinal cord. But putting this catheter in can in itself cause bleeding, and the bleeding will cause a hematoma, which will then compress the spinal cord itself cause paraplegia. So, the cure can become actually the threat itself.
One of the scenarios that can lead to spinal cord hematoma is aggressive anticoagulation. If you're thinning the blood of the patient, this can cause a hematoma. That's exactly the problem we're having here. You don't want to be too aggressive for the spinal cord, but you want to be aggressive enough in order to have profusion of service arteries. Otherwise, again, the patient dies. That doesn't really help.
In a nutshell, that was the background of our study. We sat together with our anesthesiologist and discussed the possibilities of spinal cord drainage and anticoagulation. There's a set of national, international guidelines that give us a very tight area of movement. There’s not a lot of things we can really do.
We had one scenario where we did not aggressively anticoagulate the patient, and one of the renal arteries went down. So, the patient had thrombosis, and the patient lost his renal artery. That led us to the idea that we should be a little bit more aggressive. That's what we did as a next step.
We had a set of roughly 40 patients, where we had a very clear recording of anticoagulation, spinal catheter drainage, and stuff like that, and then we changed our anticoagulation management. We added at the end of the operation a dose of aspirin.
And here comes the narrow area, where we can actually move a little bit. If you give the aspirin, the first instance you can remove the CSF drainage would be 48 hours after the dose of aspirin. We know that aspirin is active for around 100 hours in the human body, because a platelet lives around 120 hours and the aspirin does decrease the reactivity of the platelet for its lifetime.
It takes a time until they replenish. After 120 hours, your platelets are replenished; you have a new set of platelets in your body. But, with the aspirin, once given, around 4 days you can still measure that you have a relevant decrease of replatelet activity.
So, we have this window of 48 hours to 96 hours where you still have your decreased platelet activity. For the bronc vessels, you have a better chance of them not going down. Again, on the side of the spinal cord drainage, you can take it out without the bleeding complication causing hematoma, which can in itself cause paraplegia.
And the aim was to see whether the set of these patients with and without aspirin had similar outcomes. Again, in a nutshell, there was no outcome difference. The most important thing was that we had no hematoma in the spinal cord, and we just had one case of paraplegia over the whole patient group; that's 1.3%, which is very, very low in patients with thoracic-abdominal aortic repair.
Amanda Balbi: Wow, that is a lot of good information. What patients qualify for the vascular surgery? Is aspirin part of the regimen before or after surgery based on your study results?
Afshin Assadian: We have potentially 3 options of treating these patients. We can only give them medication because the risk of operation is too high. That will be option number 1. Option number 2 would be open surgery. There's still a set of patients who are certainly better off with open surgery than with endo procedures. Option number 3 would be endovascular procedures, which are becoming more and more prevalent.
Because open surgery is very complex. You need a lot of experience on everyone's hands. It's not only the surgeon; it's the whole team. It’s the anesthesiology team, etc. So, it's a big group of people who have to be skilled. And these centers are getting fewer and fewer. Also, patients demand because they want to have less invasive procedures.
So that's one thing you have to thoroughly look into patients, into their compliance, into their health state, into their anatomy, and then only then, we will decide to have a certain proportion going for endovascular procedures.
Antiplatelet therapy is the backbone of vascular medicine because it's proven that clopidogrel or aspirin or other antiplatelet agents increase the risk of myocardial infarctions, stroke, peripheral vascular events. Most importantly, if you've had a stent, for instance a coronary artery stent, you need to be on antiplatelets because the risk of these stents going down, including fatal myocardial infarction, is rather high.
Let’s say the stent has been implanted 10 years ago, this is a different story. This is a very stable chronic situation. It's totally different to a stent that has been implanted, say, 4 weeks ago. These patients need to be usually even on two different antiplatelet agents, and that would preclude the spinal fluid drainage.
It's also the guidelines; if you are on any kind of antithrombotic therapy, you shall not put in a drainage because, again, this can cause hematoma that can cause a paraplegic event. That's the reason why not all my patients are included in the study. A rather chunky proportion of them was on antithrombotics, and after discussion with a cardiologist, we were not taking them off the antithrombotics because the risk of having relevant cardiac event was too high.
Long term, after the operation, patients are on antithrombotics. So you will have a dual antiplatelet therapy after the implant for 6 weeks and then lifelong either aspirin or clopidogrel or any other antithrombotics.
Amanda Balbi: You mentioned before that you’re also working on more research to build on this study. Can you talk a little bit about that? What are you working on next?
Afshin Assadian: There are many things going on. In the past, before the endovascular era, there was 1 artery that was thought to be the one providing the spinal cord with blood. That was the artery of Adamkiewicz. So, everyone was really nerdy about this artery. But patients with progressive disease have a different blood supply.
We've seen that patients with large aneurisms have thrombosis of the arterial wall. There are actually no arteries going off, even where the Adamkiewicz has to be. There is no Adamkiewicz. And the patient is still walking around, so why is that?
So, a new concept has arisen, and that's the collateral network. There's many, many different arteries, and they're building a net, a delta of arteries that then get together and provide blood to the spinal cord. We've seen that you can even build this collateral network. One set of research is now including these arteries slowly, step by step, so that the network from above and below is providing the blood.
Actually, where you'll have the healthy aorta, then the bit in between you can replace without risk for paraplegia. That's one idea, but we also know that there's a whole area of interest in inflammation that is also very important in playing a role causing fluid shifts, for instance. We have to imagine that these big operations, even though they're just small incisions and you do everything with catheters, they have a huge impact on the equilibrium in the human body.
This will cause an inflammatory burst in these patients. This inflammation will cause many, many different things. It will be procoagulant to make them fit in the case of the inner lining of the arteries, which will actually get leaky or a fluid gets into the tissue. By doing so, it will compress the arteries and decrease blood flow. It's very complex.
But at the end of the day, inflammation in a big operation is a problem. What we are interested in is to look into the inflammatory process and see whether we can prevent it, or if we cannot prevent it, if we can dampen it or if we can get it into an area where it causes less of a problem for patients.
At first sight, it doesn't really have much to do with anticoagulation, but the inflammation has also influence on many other things where we could possibly modulate very positively a scenario for our patients.
Amanda Balbi: That's interesting and, like you said, very complex. What is the importance of a multidisciplinary approach in managing these complex patients?
Afshin Assadian: I think the most important thing is that you're open and that you understand that other people know more than you. Then, of course, there are basic scientists, nerds, who have nothing to do with patients, who are just sitting on one molecule and playing around with one molecule. And then you have to go to more simple minds, like surgeons, who just see what the outcome is.
We have to share our knowledge and our experience and work together on improving things. We all have our different sets and our different standpoints, and I think that makes it so interesting to work with people who are also not physicians; they have a totally different view of what's going on and how things should work and how they do work. That really helps us with improving.
Amanda Balbi: Absolutely. I think that's a really great point. Thank you so much for speaking with me about your research today.
Afshin Assadian: Thank you very much for giving me the time and the opportunity.