Thank you for the opportunity to present on the transvenous embolization of AVMs. The story for me on a transvenous embolization approach started with the concept of complete embolization of an AVM, also called EmboCure. This had been reported in many articles dating back from 1997 in the clinical setting, but this had also been described by Tarek Massoud as a swine model using the Ritimirably as a concept of a retrograde embolization of the AVM from the venous approach. But clearly, the reports from 1997 to more recent, they have focused on the EmboCuries. Turns out that the venous approach many times was the solution to obtain that result. Perhaps what I would like to introduce to you is that this type of treatment of stand-alone use of embolization for the treatment of AVMs is definitely challenging. And as you can see, the rate to achieve EmboCure on this series, and a lot of them were still involving only arterial approach, was not more than 50% of the cases. I think that with a significant and very variable morbidity and mortality. But I think that what we learn over time is that for us to obtain a cure of an AVM, the venous approach started to become essential to be able to deal with the different anatomies and the different type of angel architecture of the AVMs. But just going back to what an EmboCure definition is. So we had to create that to understand exactly that we're dealing with the same type of definition. And in our concept, the EmboCure is only confirmed when you have a digital subtraction geography that show no early venous filling and an MRI with contrast that shows no enhancement. So this is the picture that you can see, complete occlusion of the AVM on multiple views, as well as the MRI without any enhancement. This is a clear case of a EmboCure. It was also important to establish what EmboCure would be on the long-term. So not only you have a six-vessel angiography plus MRI done in acute phase post-embolization, but this would be confirmed at six months with angiogram and MRI. And then yearly MRIs as a follow-up in the future. So now we have the embolization, the type of definition that we're looking for. It was also important to see which cases that we were limited to do EmboCure using the arterial approach only. And so we saw that there was a significant amount of cases, almost 50% in best hands that could not be treated for EmboCure. And many times the problem was the catalyzation of the feeding artery was too risky. So either too small or too tortuous, we just didn't have the arterial access. So in those cases, we started to consider the venous approach to be able to help us to get access to an AVM to achieve then EmboCure. So I think that was a significant driver to the growth of the venous approach. Also another concern was reflux. So if you have an eloquent area with a short arterial pedicle, most treatments with embolization, they have some degree of reflux. And that was just not possible and certainly would account for significant morbidity and mortality if we didn't have an alternative. So the different types of approaches were created to decrease the amount of reflux, but certainly the venous approach helped you to minimize the reflux on the arterial pedicle since you don't have to be as aggressive on the arterial embolization. But the use of what's ended up being called the pressure cooker technique, which is either use of NBCA or coils as a plug on the arterial end to prevent reflux of the material that's been embolized. Many times this would be usually a different material than NBCA, such as Onyx or at times a fill and also the ability to use a squid increase the number of liquid embolics that are being available. But the acrylics like NBCA seem to be the best way to create a plug proximal to the embolization site so that they would minimize the reflux. This also was done with coils as a barrier. And more recently, the use of dual lumen balloons like Sceptre Mini. So these were ways to control the arterial reflux, but certainly if there was a difficulty of a complete filling the AVM, it could be complemented by using the venous approach. So I have to say that for me, it started very much like this in 2009. We published this paper that was basically the use of multiple micro catheters and to try to obtain maximum control of the embolization so that you could do that either by using two arterial pedicles or an arterial and a venous pedicle. So I think if you go back to the, I guess the history behind this is that at that point we were trying to achieve embolicures and complete control of the AVM and it really didn't matter if you're coming from multiple arterial sites or arterial venous as long as in the end the AVM was completely embolized in the safest way possible. So I think the best way to look at the transvenous approach in my mind is that this is an essential part of the embolization toolkit that we need to have. So it allows us to then address different anatomies or different angel architectures of AVMs and choose the best approach and best tools for it. So it was essential in this article to describe not only using two micro catheters, but the different approaches as well as the dual lumen balloons, the detachable tip, and then very important to, and we'll discuss this in a little bit, is that the use of imaging to be able to give a better idea of the anatomy of the AVM up front. So you can study the approach prior to. So here are some of the early examples of using two arterial micro catheters. So you can see the catheter number one in the inferior portion of the malformation. The catheter number two in the superior portion. This is all going through a combination of carotid and vertebral approach. So you have the two circulations involved, being able to progressively embolize in one session an AVM and have a complete control of the embolization. So this is very common between anterior and posterior circulation. In cases that you have in anterior subarachnoid and middle subarachnoid circulation, an AVM can be treated with two micro catheters, one in the MCA and one in the ACA, having also complete control of the embolization throughout the procedure. But of this concept of having multiple catheters and starting to take the two circulations at the same time so that you have complete control of the embolization. Now the issue was always, can you do an embolization all in one treatment or do you do that in a staged fashion? And part of the definition for us was that you have to have an ideal angioarchitecture to be able to do this an embocura. We tend to use this in mostly symptomatic AVMs that have the arteriopatical that's ideal, being a large one with minimal amount of tortuosity if possible. The ability to use also a venous access that is straightforward. So especially if it's a single venous drainage, it's an ideal candidate for transvenous embolization. If you have neidos and areas that are non eloquent, these are the best candidates for a complete embolization in one section. So this diagram is really nice to kind of share with us that on the arterial side, all the different techniques that are needed or that can help us to have a more complete embolization and certainly the detachable tip micro catheter was a huge impact on our embolization as well as the ability to use balloons and dual lumen catheters as well as the use of a pressure cooker technique has increased ability to do a better arterial embolization. Here you can clearly see that not infrequently we will add a venous approach to complement if the arterial, despite of all the advancements we have had, is not enough to completely occlude the nidos of the AVM. So instead of pushing and getting reflux or some complication from the arterial side, it's very much instead of you have two options. You can either get another arterial access early on and have two micro catheters from the arterial or you could have an arterial and a venous catheter. So the way I look at this is not about doing only transvenous embolization, but it's really more about thinking about which access you're going to have to the AVM. If that is through artery and vein, then so be it. I think you have to consider that as part of your armamentarium. This is really also from the same article, the kind of the setup, you know, it's really difficult to do a transvenous embolization as the first approach. I think that's the most, I think I would say in a very advanced level. I think as we starting with transvenous embolization, it's ideal to have a arterial setup. So you have, in this case here, some form of access to the main arterial particle to obtain a reduction in pressure into the nidus and flow into the nidus. So hereby you can use a balloon, dual lumen balloon micro catheter, or you can do a partial embolization of the AVM. So to decrease the flow on the AVM from the arterial side. In some cases that I will show an example is you can also use a systemic lowering of the blood pressure as you're approaching from the venous side. So it would not be recommended to do a transvenous approach without having some control of the arterial inflow. And that can be done as I described by partial embolization of the AVM, use of a dual lumen balloon micro catheter embolization, and with a flow arrest proximal of the AVM feeding vessel, or having a systemic hypotension either by adenosine or lowering the blood pressure as you're doing a transvenous approach. As you can see here too, on the transvenous setup, it's very important to consider an eight French axis followed by a intermediate catheter, and then a micro catheter going into the malformation nidus through the venous approach. So that is a very standard approach and very important to have the support of the micro catheter with the intermediate catheter. So another way to be, perhaps it's a little more advanced, it would be to have what's called the reversed pressure cooker. And that technique involves having a plug into the venous outlet as you're embolizing the nidus in a retrograde fashion. The main issue with that approach is that it is a permanent occlusion, you're committed to occlude the AVM, otherwise you have an outflow obstruction that it could be an issue if the AVM is not completely occluded in a very efficient way. So I would recommend perhaps a more, not as a permanent occlusion of the venous outflow until you have a better penetration of the nidus and arterial control. So this is a very nice diagram that shows the ability to, the different types of anatomies that especially in fistulas, I would say that you can encounter. And then the position of the micro catheter could alter if you are basically having the number of veins and arteries relationships, it's really interesting how variable that can be. And also could potentially dictate how deep you place the micro catheter into this so that you can have a more efficient way to occlude all the malformation. And I think to be mindful of that, it's really important to have great imaging. So here you see the 3D DSAs that we can obtain today that have great detail and allow us to map the arterial and the venous maps up front. So you can actually really see what's coming in and out. But this is a static picture in 3D. So the 4D DSA, as you can see here, this is a tremendous improvement on our ability to understand since you played the spatial resolution of a 3D into a dynamic view of a regular angiogram, so you can play back and forth these in different angles and see the inflow and the outflow. So you can see your early phase and then a more late phase and then rotate this as needed. One of the things we didn't see, we didn't have access today is this one here, which is the ability to see flow into the AVM. So now you can also see which venous particle has more flow and that can help you to also determine as you're decreasing the flow into the AVM, but also the ability to choose which vein may have a higher degree of drainage of that AVM. I think this information was just not much available before and having this in a three-dimensional way with the iFLOW map on top of it, it really helps you to start deciding which particles to catheterize and how much of an impact you have as the embolization is going on. But certainly for planning is extremely helpful. Then, I think this is, you know, in the best cases that I have to illustrate as an ideal initial case for transvenous embolization as a symptomatic, so a deep AVM that had presented with a hemorrhage. So, you see the arterial particles are very small, but the venous drainage looks very favorable, and as you can see, we tried to do a catheterization from the arterial side, and it's really complex. We were able to get, this is early on in our experience, and I think that there was a fear from us to just do a venous approach alone, so in this case, we started with a partial embolization from the arterial side, and now we have just a residual, but instead of accepting any reflux, we basically stopped the arterial embolization and had a venous approach to then complement the treatment of the AVM. This type of AVM, I will show multiple examples here, it's another one. It's a really great application for the transvenous approach because, and I think today, knowing what we know, we already placed the two microcatheters in position, so you have an arterial and a venous approach at the same time, so you can see the original AVM here, and then the embolization. I think it's always wise to start with the arterial embolization and decrease the flow in the AVM, and then complement with the venous, but the more we know about this, it's very possible that you could embolize through a transvenous approach, such a small AVM, and this is a little bit larger one in very eloquent areas, but you're able to basically obtain a complete control of the AVM having arterial and venous approach. The venous approach tends to be very straightforward if you use a microcatheter. We tend to use either a dual or echelon 10, always with an intermediate catheter and eight French guide catheter, and this is, you know, the follow-up in six months showing complete occlusion. A more complex case is this one, also symptomatic AVM with a larger basal ganglia bleed. We decided to, before go to surgery, to embolize the AVM, and there was really no good arterial access, so we had a plan to go to surgery for decompressive hemokraniotomy and the hematoma evacuation, so prior to going to the OR, we, as you can see here, we really had no good arterial access. There were very small features, so after studying the AVM with our 3D and 4D technique, we decided to go ahead, and here you can see we use a benchmark six French guide sheath. We tend to go more to eight French now, but in this case, we use a cat six intermediate catheter in a septal balloon and place the balloon dual micro catheter into the venous outflow. This was very close to the nidus, so we were able to navigate really close to the nidus, and under the adenosine cardiac stem still, we were able to inject with balloon inflated, retrograde, and fill the AVM basically from the venous access, so this is a relatively large AVM to do transvenously, but I think with the use of the adenosine and a reflux control in a retrograde fashion, so this would be a little bit of a venous and arterial systemic control, we're able to embolize AVM, and I felt that, you know, we would still go to surgery to do the, this is the final result, so you can see a complete embolization of the AVM, and allow us to go to surgery to do a hemokraniotomy with evacuation hematoma without having to go into the AVM site. This was completely occluded, as you can see on the follow-up. The patient ended up going home within seven days to, I'm sorry, going to rehabilitation within seven days, and had hemiplegia from the original hematoma. I think that this was a really nice way to get rid of the AVM and care for the patient in an acute phase without having to deal with this AVM later on. The follow-ups and the durability of this treatment is important to be confirmed by using angiography at six months, as well as MRIs on a yearly basis. Now, I think transgenic embolization is still evolving, and the use of smaller balloons, you saw a regular scepter being navigated in the venous anatomy, but this technique of using dual lumen balloons, especially smaller ones, is evolving, and you can see here that the use of the mini scepter is really exciting to us. This is just becoming available now. So these smaller balloons can get us closer to the nidus from the venous approach and allow for a temporary embolization different than, in this case, you're using an embolization plug like NBCA or coils. This one you can deflate and not have a commitment to have this venous outflow occluded in case you cannot obtain complete occlusion of the nidus. So the mini balloons are going to be really exciting to be able to partially control the vein reflux and also taking consideration that Aruba has changed our approach to treatment of AVMs, and I think this slide summarizes a bit of the concerns that were raised from Aruba trial. The risk of increasing embolization, any type of treatment in terms of the death and stroke and functional deficits was what the trial kind of raised, the concerns that are we choosing the best treatments, and I think this forced us to improve our techniques as well as try to get ready for what I think today is this big question is, you know, like when, what patients you select post Aruba. Certainly on the Aruba eligible patients, we are treating 65% of those patients medically, so we're not offering as many interventions for the Aruba eligible patients, and I think that is a big change. Most of the cases I showed you are symptomatic post hemorrhage cases that the venous approach serve us very well to treat those cases, and these are some of the examples of when to treat Aruba eligible patients, and I think here you can see the presence of aneurysms, it was one, the issue of venous stenosis is another one. If you have problems with clinical symptoms, certainly any focal deficits, headaches, and I think that it's really important to consider that. The other possibility is the issue of family planning, it's a consideration in young women. It's certainly worth to discuss that indication with the patients. The main thing for me is that AVMs, they have to be managed in a way that we have some type of understanding of our risk for embolization, so the AVMES is a classification that we published trying to quantify the risk of embolization, and so based on that score, we and Spatz and Martin together, we tried to figure out when to do radiosurgery, embolization, or surgery for AVMES, and here's a little bit of how we stratify that risk and for the type of AVMES based on the different classifications, and we tend to treat AVMES in an acute phase after a hemorrhage, and that is, as I demonstrated here, seemed to be helpful to get the patient cared for in a single session while they're sick from their intracranial hemorrhage, and we have seen really good results long-term without having to worry about the residual AVMES or issues that many times are a concern that you're not able to see the full AVM after intracranial hemorrhage. That may be true, but it seems that the approach we're taking is taking care of the AVMES without us seeing so much residual or issues on the follow-up angiograms after resolution of the intracranial hemorrhage. I think that today, the space of AVM treatment is very similar to what we were in acute stroke a few years back, so we still will need to standardize our approach more and understand the indications so that we can then move on into trials to demonstrate the impact we're having on this very challenging disease. Transgenus approach is definitely part of our toolbox, and I think this seminar is very important to emphasize that this approach is likely to be something that we need to master to be able to offer more treatments to our patients that otherwise would not be possible from the arterial approach. So it really expands the embolization technique to more patients and more patients that have an angioarchitecture that is not favorable from the arterial side to occludonitis. So the venous approach has been incredible to achieve more AMBO cures, but also I think it will benefit from better technology and imaging and devices that is improving in a very fast pace. So you're seeing new liquid embolics as well as new catheters and certainly the imaging also to delineate the AVM and planning of the surgery is extremely important. Thank you for your attention.

transvenous embolization

arteriovenous malformations

EmboCure

venous approach

embolization techniques

AVM treatment

imaging techniques