Virtual Reality to Predict Paravalvular Leak in Severe Bicuspid Aortic Valve Stenosis in Transcatheter Aortic Valve Implants: An Interview With Sergey Gurevich, MD

Dr Sergey Gurevich shares background and insights on his paper, "Virtual Reality to Predict Paravalvular Leak in Severe Bicuspid Aortic Valve Stenosis in Transcatheter Aortic Valve Implants." Read the article here.

Transcript:

My name is Sergey Gurevich; I am an Assistant Professor of Medicine at the University of Minnesota. I'm also an interventional cardiologist at the University of Minnesota. I'm here to talk a little bit about our most recent article, which is titled "Virtual Reality to Predict Paravalvular Leak in Severe Bicuspid Aortic Valve Stenosis in Transcatheter Aortic Valve Implants."

00:40: Could you please give a brief overview of your study?

What we tried to do in this current study is to see if we could predict and prognosticate some of the complications that are associated with transcatheter aortic valve replacement. In particular, in this study, we wanted to use some novel software that has recently been FDA-approved and has been on the market for a little while — and that we actually used in our research before it was FDA-approved. That software allows you to bring in the CT reconstructions that we do prior to our transcatheter aortic valve procedures and reconstruct not only the kind of the patient's valve and heart and the aortic structure, but also able to reconstruct the valves themselves. This allows us a lot more flexibility in terms of using different types of valves, different sizes, and different types of implants in terms of the depth of implants as related to the valve annulus itself.

Once the valve goes in, the model can then be examined in multiple different dimensions. This allows you to basically turn it upside down and look inside and really closely examine it for any malposition that can happen. happen between the valve frame itself as well as the aortic annulus. There are different steps that you can use afterwards as well to sort of improve on that visual analysis, but that is kind of where it starts.  We went through and we did this in a number of patients for the study as a continuation of prior research that we've done with physical 3D implants, where we used physical stem frames and valves and implanted them in 3D models. And this basically skips a step of 3D printing and goes into a totally virtual world where you can do this. Once the implant is created, we then analyze it.

And so, in our study, we picked a particularly challenging population, which is the bicuspid aortic valve patients — which is again, the most common congenital aortic valve anomaly that we see in our patients, so it's quite common and severe aortic stenosis is very common in these patients. And because of the elliptical annuli that exists in these patients, the malposition of the kind of valves that are designed for a more spherical circular annulus is very common. And so paravalvular leak has long been a common problem in these particular patients.

In this study, we had a number of patients that underwent these procedures; we reconstructed all of their images, and basically performed all of the implants virtually as though they were happening in the lab. After that was completed, we then examined them and we could see areas where malposition happened, where it didn't happen, and where we would expect to see PVL or paravalvular leak. And then we compared it to existing data from those same patients, both echo data and CT data, analyzed all of that for PVL as well, and then compared the 2 different scenarios, one where this all happened in the cath lab and one where this was all virtually duplicated. And when we compared them all together, we could very accurately predict that at the end of the procedure, the patients that we expected to have PVL actually did end up having PVL on both echo and CT and malposition in the areas that were predicted. So, with that analysis, we compared it to our prior study, which was done with 3D implants, and showed that this is as good if not better than that, except for you get to skip the step of 3D printing. And when you compare it to the real thing, which is doing the implant first, and then looking for PVL if it happens, this is a 1-to-1 comparison. So, it's just as good as doing it in the procedure as it is doing it in real life.

What that allows you to do then, is if you could simulate these procedures ahead of time, before doing the procedure, you could isolate those patients that are at higher risk for PVL occurrence and rethink the approach. Whether these patients go to surgery or whether these patients can have a different valve potentially that can accommodate a more elliptical annular or whatever the problem is, or potentially even prepare for that if there is PVL, then you could potentially post-dilate the valves or even expect that you may need to do something else such as a plug to close the leak.

So, there's a lot of potential benefit for doing this ahead of time. And of course, this is only one thing that you can apply this kind of a system to.

06:25: Why do you think cardiologists have not yet widely adopted virtual reality for TAVR planning?

I think that this is actually a very similar question that we had when we discussed a prior paper of mine looking at 3D printing in similar types of patients. And at that time, the question was, well, you know, why is 3D printing not widely adopted? Though it is used, and I think virtual reality is also used in the interventional arena as well and the structural arena, I think, as with any new technology, it takes time for it to be adopted by medical specialties. And when you're talking about potentially doing interventions, I think there's much higher risks. So, there's a much higher bar for using these technologies on these patients because the potential risk of making a mistake with the novel system is very high and could potentially be life-threatening. Of course, this kind of is a little bit of a step back in the sense that you're doing this to prognosticate, but if you're making decisions based on which valve you choose and in which route you go, whether it's transcatheter or surgical, that then of course has lots of ramifications for the patients.

Having said that, I think that the virtual aspect, the virtual reality aspect of it, is very unique and I think it's very new and unlike what we talked about last time with the 3D printing, I think the virtual reality is a little bit more palatable. It requires less resources and less kind of specialty skills to use it and deploy it very rapidly. So while it's not widely used as of today, I think with the amount of medical technology and medical software that's coming to the market in the space, I think it will be commonly used probably in the coming few years.

08:40: Of the various periprocedural complications associated with TAVR, why did you choose to focus on paravalvular leak?

PVL has long been a problem with transcatheter valves. When the valves initially were first designed and deployed en masse and FDA approved in the US back in 2011 or 2012, very quickly physicians and patients noticed that PVL is a big problem. And at that time, with the earlier valves, the problem was much, much higher. You could have PVL happening in as many as 10% of the patients that end up with these procedures. And the question then becomes is, if you have PVL, how bad is it and what does that mean for the patient? And when we have those analyses done, we saw that it carries a mortality associated with it.

So, if you had PVL that was moderate or higher in those patients, the mortality for those patients was much higher. And so the valves were redesigned to try to reduce the PVL. And then all the major valve manufacturers nowadays use basically the same technique to try to prevent PVL. And as they as they did that the PVL went down dramatically. But there was still a question of mild PVL and PVL that is moderate that goes unnoticed. And so the question is how does that happen? Studies afterwards showed that even mild PVL could potentially cause big problems for patients, maybe not as much of a mortality change, but there was an associated risk of stroke that was seen in studies that were done with the Boston Scientific valve, which was the Lotus Valve at the time.

And then the other problem is, what if you have moderate PVL, but it's unrecognized by the technique that you're using to sort of track it. There's literature showing that, but even in practice, we've had a number of patients that have had valves placed, where there was no PVL at the beginning, and then 2 years down the line, patients came back in and they had moderate to severe PVL. And those patients needed at that time a different procedure to fix that because they were coming in with heart failure at a 2-year mark. And if you go back and you look at their CT scans and you reconstruct them using this software —this is one of the things that I did—and in both patients you can correctly identify where the PVL was happening and the degree to which you can see the malposition in that area. So, you could estimate how bad of a leak you are going to have around the valve. And the problem became that the transthoracic echoes, which are basically the way that most labs and most hospitals assess for PVL, in those particular patients, the quality of the images was not sufficient to identify the PVL — there was no color jet that could say that yes, there was a lot of leak. You simply saw a lot of just poor quality imaging. And you could not say for certain, you certainly couldn't see the leak, but you could also not say that it wasn't there. And when you look at it closely in these reconstructions, you can definitely assess that.

And so, PVL is still to some extent a big problem, but it's also relatively easy to study when we look back on some of the patients that we have. And it's one of the key targets that I think that still has room for improvement. And with it carries a lot of mortality and morbidity both with cardiac death and also with stroke.

12:50: What other applications do you foresee for virtual reality in interventional cardiology?

I think that there is a wide array of applications for this technology. I think virtual technology, just like any sort of imaging modality, can be extended into almost every part of interventional cardiology as we rely extensively on imaging techniques, both while doing procedures and while preparing for procedures.

You could apply it to areas where understanding the 3D structure of a particular area of the heart becomes very crucial to these structural interventions. As an example, the left appendage closure devices rely a lot on 3D transesophageal echocardiography to look at what is the structure of the appendage and how best to close it and whether or not leaks can happen there. If you look at the mitral valve, that valve in particular has a lot of dynamic motion and through-plane motion. Understanding of that 3D structure is very important and you could bring all of that into procedures, but at the same time you could use that 3D data before the procedures as well.

Now I don't particularly expect that you're going to have a lot of interventional cardiologists wearing virtual reality headsets in the procedure because they do obstruct view and we do need to see patients but augmented reality, which is, if you want to put it simply, kind of a see-through way of looking at virtual reality while still seeing the environment around you —or mixed reality as sometimes people refer to it —that has the potential of coming into the cath lab or the operating room even and being used as a tool to both guide procedures and perform them.

If we're looking at the radiology part of it, the pre procedure planning part of it, I think virtual reality offers a lot of—I think it simplifies what a lot of the radiologists and cardiac radiologists are doing. It takes a 2D image off the screen and puts it in front of you. And basically there's no such thing as 2D radiology. Most of the things that we do either have 3 dimensions or we need three dimensions to really understand it. And when you remove the 2D aspect of it and you bring it alive in front of you, where you can move it in any different way and examine it in any way. different way, that becomes very intuitive for us.

And another thing that virtual reality does is it simplifies things. It allows you to use simple, for instance, hand motions to hold or go through the image. And that really takes away from having to rely on confusing and complex tools that take time to learn. And so in my lab, we have a lot of cardiology fellows that work and train on the software and it's very intuitive and very quick how fast they can get a handle on the software and use it as an expert in just a a few sessions.

So, I think there's a lot in terms of clinical applications, but I think there's a lot also in terms of training. Imagine having a fellow or interventional fellow or general fellow getting the experience that they need and performing the procedures and understanding things like complications and technique and correct procedural workflow before actually stepping into the cath lab. And instead of making those mistakes there, they can practice in a virtual reality setting.

16:45: What can we look forward to seeing next from your group?

One of the things that we're working on now is taking these 3D reconstructions that we do both in the 3D printing arena, but also in this virtual reality arena, and using the models that we generate from them to put them in a different simulation. So instead of having just virtual realities, looking at the structure of things and seeing how things fit together, we can also do computational fluid dynamics. In other words, where we can simulate the flow of blood through these areas, whether it's the arteries or the valves, or the heart. And what that allows us to do is, as an example, in the PVL arena, not only tell us where there's malposition in the valve, how big that malposition is, and give us an assessment of that, but it can also tell us what's the flow rate through that area and how much PVL, with exact certainty, are we able to assess.

Right now, when we do an assessment in 2 dimensions of PVL and we assess how bad the PVL is based on circumference of the aortic annulus and how much of it is affected by the leak, that is very well known to be highly inaccurate, and what this tool will allow you to do is quantify how much reflux happens. And we can do that much better than what either transthoracic or transesophageal echocardiography can do. So, you can tell how much volume of blood is being refluxed, and that helps you to detect how bad the PVL is and puts these patients in different risk categories. If there's mild PVL, but there is some malposition, these patients will probably do just fine with some adjustment of the valve. But if the leak is substantial and there's no way to reduce it, then those patients could potentially go and get surgery instead.

19:05: Is there anything else you'd like to share with our audience?

I think one of the big things that is going to be happening in the medical field, the surgical field, and the interventional field is more reliance on mixed reality, virtual reality, or augmented reality. And I think that's going to be big. I think a lot of consumer electronics are now coming out with these devices. We can tell just by looking at the tech arena that this is something that is going to be present in one way or another, whether it's going to be, you know, Microsoft HoloLens or Apple Vision Pro or any number of those devices. We also know that it's going to be happening in the medical arena as well. There's a lot of different companies like Philips and Siemens that are working on their own versions of augmented reality software that can then be likely ported to a lot of these systems.

When we go into the cath lab or the operating room now, what we see is a lot of big television screens all over the place. Ten years ago, these were all vacuum tube TVs or CRTs. Now they've all transitioned to flat screens, LCDs, and LEDs, and probably in another 10 years, what you're going to see when you walk into these rooms, you're not going to see any TVs at all, but you are going to see a lot of people using projections of one kind or another, whether it's wearing glasses that project a screen in front of you or information in front of you, and using that technology to navigate the procedures, help you guide your procedures and perform surgeries.