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Obsidio Embolic in Lower GI Bleeds: Applications & Advantages
Thomas "T.J." Turner • May 5, 2024 • 38 hits
Gastrointestinal (GI) bleed embolization is a minimally invasive technique used to stop life-threatening bleeds under image guidance. During this procedure, choice of embolic is case-specific with different embolics serving different functions. For example, particle embolics can achieve appreciable stasis of blood flow in microvascular beds, but pose higher risk for off-target embolization and tissue necrosis. What then makes a suitable choice of embolic when addressing bleeds of the lower gastrointestinal tract? In this article, Drs. Kevin Henseler and Aaron Fritts go over the basics of embolic choice for these challenging cases and the emerging role of Obsidio, a novel embolic technology with promising use-cases for lower GI bleeds and beyond.
This article features transcripts for the BackTable Podcast. We’ve provided the highlight reel here, and you can listen to the full podcast below.
The BackTable Brief
• For lower GI embolization, coil embolization is normally recommended given decreased risk for end organ damage and ease of deployment.
• Obsidio is an injectable, cohesive solid, able to flow under high pressure like a liquid through a microcatheter and then form a solid upon entry into the blood vessel. Obsidio is one product in a growing list of semi-solid and liquid embolics that may become more commonplace in IR suites in the near future.
• Injectable solids can be combined with preexisting embolization techniques to improve technical success in certain patients.
• A complete list of indications for injectable solids is pending, but there are many cases that could benefit from the ease-of-use of injectable solid embolization, even outside of GI bleeds.
Table of Contents
(1) Standard Embolization Devices for GI Bleeds
(2) Emerging Solutions for GI Bleeds: Obsidio Injectable Solid Embolics
(3) Obsidio: Current State & Future Indications
Standard Embolization Devices for GI Bleeds
Traditionally, coils have been the preferred embolization device due to their lower risk of inducing ischemia and end-organ damage in the colon, compared to other embolic materials like particles. Embolic glue has also been used but complicating factors such as catheter adherence have made this a technique that is more reliant on sufficient experience of the operator with the embolic material.
[Dr. Aaron Fritts]
Let's get into the meat of it in terms of embolization devices, we've talked a fair amount previously on the show about detachable coils. We've talked about glue, actually Ziv Haskal was on the show talking about glue and you're going to help talk about new product that's soon to be on the market, but at first before we get into the new stuff, I want you to tell me what's been your traditional go-to embolization device for lower GI bleeds?
[Dr. Kevin Henseler]
Clearly coils. You hear or you see some research about particles which makes me cringe because I'm just so concerned about end-organ damage of the colon and causing ischemia. For me, it's always coils. Glue, I'm not a gluer, it's interesting when I went through fellowship, that was the time where people were gluing catheters in place and so glue was very, very high risk. We just didn't do very much glue. I think as Ziv said, I listened to that, if you have any desire to do glue, you should, by all means, listen to it. I must listen. I think he's right. It's not to be trifled with.
If you have glue in your training and you are very comfortable with glue, I would work hard to keep that skill set up because once you lose it or if you didn't get it, getting the experience with glue is a very, very tough road. If you've got it, try to keep it. If you don't have it, you got to be careful about trying to learn with glue because it's very operator dependent. There's a lot of variability. What dilution am I going to use? Am I going to have glue stuck on the end of the catheter that's going to embolize, God forbid am I going to glue my catheter in place? I tend not to use glue. For me, a lower GI bleed is a coil, a coil, and a coil. That's really all I'm going to use.
[Dr. Aaron Fritts]
Detachable, like you said before with the upper GI.
[Dr. Kevin Henseler]
Although there are times where when you are, if you can get very, very far out into the vasa recta, I'll put in just like a–
[Dr. Aaron Fritts]
Two millimeter Hilal or something.
[Dr. Kevin Henseler]
Two millimeters straight coil. Those are great cases and you're done and you're out.
[Dr. Aaron Fritts]
I love those, those are my favorite, those little and you can just shoot them in with a little syringe. Let's talk a little bit about this new embolization product that's coming on the market here shortly called Obsidio. Just give our audience a little bit of background about the product and how you became involved with it.
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Emerging Solutions for GI Bleeds: Obsidio Injectable Solid Embolics
Obsidio is a novel injectable solid embolic with cohesive properties, allowing it to adhere to itself rather than surrounding tissues and materials, offering a more controlled application compared to traditional liquid embolics. Obsidio's primary distinction lies in its viscosity which allows it to flow under pressure through a microcatheter and revert to a solid state upon exiting. This unique behavior enables precise localization near the catheter's tip, minimizing the risk of distal migration even in high-flow vessels. The radiopaque product is designed for permanent placement and offers significant advantages in settings requiring embolization in anticoagulated patients, according to Dr. Henseler. Its versatility, coupled with the lack of a need for specialized catheters, may position it favorably to grow as an important tool in emergent embolization procedures.
[Dr. Kevin Henseler]
I live in Minneapolis, which is the headquarters of lots of endovascular companies, Medtronic, Boston Scientific, has a big presence here. One of the opportunities here is to be able to partner with industry a little bit and help them with work. We also have one of the largest animal labs in the country in Minneapolis. I dabble in some preclinical work doing animal labs.
I was doing some work and was evaluating this product and it was part of a group of products I was evaluating. The CEO after we were done reached out to me and said, "I'm looking for some help in continuing to formulate this product and working with it. Would you be willing to do that?" I said, "Yes, of course." It was a product that was already formed but needed some tweaking. We did iterations where you talk about glue, glue is adhesive, it's sticking to things. Obsidio is an injectable solid and I will maybe get into that a little bit more, but it's more cohesive. It sticks to itself. We would go through iterations saying this isn't sticking enough to itself or this has now become too sticky too.
We work through iterations of that. Then I ended up working with the preclinical and FDA approval process, getting all the animal research for the indications of hemorrhage and hypervascular tumor. Have quite a bit of probably have injected it in several hundred arteries. The company was purchased by Boston Scientific and Boston Scientific, I believe, intends to have the market launch of the product fairly soon. That's my background with it.
What is it? Obsidio is not a liquid embolic. When we've been talking about glue, we're talking about liquid embolic. When we talk about Onyx, we're talking about a liquid embolic. With Obsidio, it's an injectable solid. What it is, it's like peanut butter in a 1cc syringe. It's very, very thick and viscous. When put under pressure, it flows like a liquid. It can go through a small microcatheter. Then once it exits the microcatheter, it moves back to that solid state.
The physical properties of Obsidio are such that it is not going to flow very, very distally like a dilute glue would. It would function much more like a more thick viscous glue material. It's going to generally stay near the tip of the catheter. If there's a high-flow vessel, some of it will shear off, it will go distally, or if you're injecting it very, very slowly, you can have the blood supply move it very distally and fill up an entire vascular bed.
[Dr. Aaron Fritts]
It reminds me of cement with kyphoplasties. Just the way you're describing it, PMMA, it's got that toothpaste-y consistency.
[Dr. Kevin Henseler]
Exactly. You'll inject it when you see it, when your rep comes and shows it to you, you'll put it on your finger and it's just like that. It's like that toothpaste or peanut butter, very, very viscous, thick material. The genius of it is that biomechanical ability to have it flow and be a fluid when it's under pressure in your microcatheter.
[Dr. Aaron Fritts]
Got it.
[Dr. Kevin Henseler]
What that means is that it's very controllable because as soon as you stop adding the pressure, then everything stops, everything is in place. There's no adhesion, so it could sit in your catheter for as long as you wanted to do, and then you can continue the embolization. One of the things that I think is interesting about the material and exciting is that we just talked a little bit about glue and about the high risk but high reward of glue and how much you have to be really well trained in it because bad things can happen.
I think that Obsidio is a product that de-risks that a little bit where it's going to be something that people after two or three times using it are going to start to feel pretty comfortable with how it works and when they're going to use it. Lower GI bleed, we like to think about this in a smaller vascular bed, maybe vessels less than 3 millimeters. I think it's going to be a great product in GI bleeds and a lower GI bleed. It is catheter agnostic, which is nice. One of the things that's a little bit frustrating is some of the detatchable coils they use, you're supposed to use the product's designed catheter, and that's not always the catheter you want to use. That's another advantage.
There's some real advantages, and I think in these situations, we're going to learn more. It's not just Obsidio, there's going to be a lot more coming out. There's a lot coming out in the liquid embolic market. I just said, Obsidio is not a liquid embolic, but in that whole market basket, a lot is coming out. I think it's going to be really important for everybody, new and old interventional radiologists, to understand what these products do, which products you think you're going to want to invest your time into learning, because let's just say a year from now, there are four or five different materials like this, you can't get good at them all. You're going to have to figure out which ones do you want to invest the time.
I think Obsidio is going to be well-positioned in there. It's got some advantages for coils and that you can be anticoagulated. It's physically filling the vessel lumen. One of the–
[Dr. Aaron Fritts]
Is it permanent?
[Dr. Kevin Henseler]
It is permanent. One of the things that [crosstalk]
[Dr. Aaron Fritts]
Is it radio opaque?
[Dr. Kevin Henseler]
It is. There's tantalum in it. The tantalum is premixed. It's microlyzed tantalum so that you will be able to see it. It is not as dense as Onyx. There's not as much beam hardening artifact. You get a CT and you'll see it in place, but it won't be this big starburst, another advantage. With the anticoagulation, you can use it in anticoagulated patients. As you know, coils really are frustrating in anticoagulated patients, even patients on Plavix and aspirin, which almost all of these patients, not with their lower GI and their upper GI, I believe, they're all on aspirin and Plavix. This is going to help. It may end up being an adjuvant.
You put one coil in, and then you put some Obsidio behind it in an anticoagulated patient, and you've got yourself a very secure embolization.
[Dr. Aaron Fritts]
Sabeen got to pilot actually yesterday and I was messaging with him because I was asking our team of hosts for questions about the new product. Sabeen said, "Really cool game changer." He said, "Very easy to use. They just did a demo on the back table." He was saying, even though it just said multiple times it's not a liquid embolic, he said best of Onyx and best of glue. It takes away the annoying stuff from both of them. He does have specific questions for you. He wanted to know, if there's frank bleeding extrav, like a large bleed, you did mention that this is going for small vessels at this point.
In the animal studies, have you ever seen product extrav into the space or into the GI space when maybe too much is injected or anything like that?
[Dr. Kevin Henseler]
We haven't. Again, because it is cohesive. Even though it will get out to, and I can't quote off-hand into the 30 or 60-micron range, it is not liquid, so it is not going to extravasate out into. Now, if it did, I don't expect that there'd be a problem because we have animal data six months out that just shows that in the vessel there's remodeling and the tantalum is left, and it's a gelatin base and so that all goes away. Even if it did move out into the lumen or out extravascular, I don't think that's an issue. It's an inert ingredient, it's got four ingredients and none of them are toxic in any way, so that shouldn't be an issue.
[Dr. Aaron Fritts]
Does it need to be refrigerated?
[Dr. Kevin Henseler]
Again, that's one of the geniuses of the product and I didn't develop this product, so I'm not taking any credit for that. One of the geniuses of the product-- you just take it off the shelf, they recommend storing it refrigerated. It has a shelf life out of the refrigerator several weeks to months, and they're working on how far out it can be out of the refrigerator. If you have it in your refrigerator in your lab, and you just hold it in your hand and warm it up for 30 seconds, that's really all you need to do, and then it's ready to go. It is in the syringe. It is all mixed up. It is one of the nice things about this in something like a GI bleed.
Some of the other things we've talked about, Onyx clearly is not a great product for this because you've got a huge prep and some of that could happen as you're getting things ready, but probably not terribly practical. Glue, while not taking as long, it is a little bit more fussy when someone's bleeding out. You just have the tech opens the package, they hand it to you, you put it on your catheter, and you're done. One of the things I love about it is you can see it because of tantalum. You know that when it fills the vessel that you've occluded it.
For instance, you've got, let's say, a lumbar artery or a lower GI bleed that you see, you ask your tech for the Obsidio, you put it on your catheter, you fill the vessel, and it might take 0.1 cc to fill a vessel, not often 0.2 ccs. Then you pull your microcatheter out and you're done. We're talking 60 seconds, 90 seconds, less than it takes to prep and get your coils in. It's a really fantastic product with a lot of upside. Downside is that it's sitting inside your microcatheter. Unlike a coil, you're not able to do a run after you have injected this.
Certainly, as we get more and more experience with that, there's no reason that you can't use a sandwich technique in this and put a 0.1 milliliter in and then keep your lumen open. Right now, there's not a lot of data on that. To be on the safe side, you're injecting it. Then, if you've got three or four different spots, that may not be the perfect solution. If you can find the bleeding, it's a great, very quick, and very sure. You take your gloves off, you high-five the techs, and you're out.
[Dr. Aaron Fritts]
I guess you could have a Tuohy on and do an injection to your base, right? If you have your microcatheter.
[Dr. Kevin Henseler]
Yes. Absolutely.
[Dr. Aaron Fritts]
You could do that? Yes, that's really interesting. For example, glue on the Ziv Haskal episode, Ally Baheti, who was the host of that, she pointed out that Ziv suggested portal vein embo for somebody who's just starting out using glue for embolization, what do you think for Obsidio going forward as this product comes to market would be for somebody using it for the first time. Would it be a lower GI bleed in this case, or is there something else that you theorize would be a good first case for new users?
Obsidio: Current State & Future Indications
Injectable solids like Obsidio, which shift from a solid to a fluid state under pressure, offer a unique advantage in their ease of use and quick learning curve, allowing clinicians to quickly gain proficiency, often within a few cases, according to Dr. Henseler. Clinical scenarios where small, localized bleeds are utilized, such as in renal trauma or pseudoaneurysms, will likely be amenable to embolization with injectable solids. The potential broader application of injectable solids include correcting endoleaks, for example, suggesting that its versatility could make it a valuable addition to the interventional radiologist's toolkit.
[Dr. Kevin Henseler]
I think a great first case for Obsidio would be your run-of-the-mill lumbar or inferior epigastric bleed where you have an appropriately sized vessel, you have relatively straightforward anatomy. I think that's the case where you can really see what the material can do in a very safe area. I like it for those-- for small trauma, muscular bleeds, those things. One of the things that I would just caution people with this new product, we talk about vessels less than 3 millimeters or 3 millimeters or less for a reason, and that is this does interact with a wall of the vessel and in vessels that are prone to spasm, you can spasm with this material in.
As you can imagine, as we've talked about, this is like toothpaste. If you have the vessel filled up all the way to its origin and then it spasms, you can spasm the material outside and get some misembolization. When you think about, well, what are the first cases I'm going to do? Those are some of the things that I think you should consider is, how safe is my access? Do I have enough space? I don't want to do this right before a critical branch vessel or anything like that. I think the trauma, the renal traumas, the spontaneous retroperitoneal bleeds, I think those are going to be great first cases for Obsidio.
I'm never sure if I'm right about this, but we talk about a steep learning curve, but I believe that actually a steep learning curve, we think that means that it takes a long time, or it's hard, but a steep learning curve is what you want, which means it's really easy to get up to proficiency. The quicker you can get to proficiency is the steeper your learning curve. I think this is a very steep learning curve. It's going to take you one or two cases, and you're going to go, "Oh, yes. Okay. I got this." Even as you talk about Sabeen, just even at the back table , you're going to get a really good feel about what is this doing. I think that's one of the things that make it very easy to approach as a new product.
[Dr. Aaron Fritts]
Yes. As you were talking, I was thinking about the renal trauma is also a great example, I think, too, because those are typically tend to be small, pseudoaneurysms and you're trying to get real subsegmental as you can. The epigastric, that's a great example, I think too.
[Dr. Kevin Henseler]
As the product has more use and there is limited human data, there's a lot of great lab data, but that's going to come quickly. It's interesting to see, I think that this will be something that people will be really interested for endoleaks. I think there's lots of other things that are off-label. As interventional radiologists, we look at the instructions for use once and then throw them away and forget about them. We will continue to do that, as we have always done, I think there's a lot of interesting uses for the product that will be coming forward.
Again, I think one of the things just to keep in mind is this will not be the only product coming out, there will be others. It's going to be important to figure out where you're going to invest your time, which of all of these new products, you're going to have to decide which products do I think are going to work well in my armamentarium. How am I going to use them? Which ones are the most versatile and the safest and easiest for me to learn? I think that Obsidio ticks a lot of those boxes.
[Dr. Aaron Fritts]
What I've heard is May to June, there's going to be 100 human cases in 30 centers and then a limited market release after that. That's exciting. That's really next month that we're looking at. I imagine yours will be one of those centers.
[Dr. Kevin Henseler]
Yes. Again, I've been able to use it in the lab a lot and feel very, very comfortable with it. I'm excited about the prospects of a new tool in our toolbox. Again, as an old guy like me, learning new tricks is fun.
Podcast Contributors
Dr. Kevin Henseler
Dr. Kevin Henseler is an interventional radiologist with Midwest Radiology in St. Paul, Minnesota.
Dr. Aaron Fritts
Dr. Aaron Fritts is a Co-Founder of BackTable and a practicing interventional radiologist in Dallas, Texas.
Cite This Podcast
BackTable, LLC (Producer). (2023, May 12). Ep. 321 – New Innovations in Lower GI Bleed Embolization [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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