So I'm going to switch gears a little bit and talk about deep venous interventions and talk about some approaches to improve outcomes. So we've talked about the deficiencies of angiography, both on the coronary side, even on the lower extremity arterial side, and the same applies in venography as well. It's just not enough completely, and I would even say that this is much more exaggerated on the venous side as these vessels get larger, and three-dimensionality is extremely important. So Peter Neglin, who's a big name within the venous space, said, we develop strategies to compensate for the shortcomings of venography and convince ourselves it's adequate, and I think that's what we often do. We try to find ways to say this is enough, but we know that in many aspects, just doing venography alone doesn't allow you to really recognize the extent of disease. So data suggests that 30 to 50 percent of cases can be missed if only AP projections are used for venograms, and this has been shown even through Raju's study, actually showing that if you go by collateral, some people say, you know, we base the degree of obstruction based on collaterals in these deep venous space, that you can miss, you know, majority of these lesions as well. And I'll go more into data, but why do we need to use intravascular ultrasound on the venous side? Well, it gives us a lot of information, both about size and as well as morphology of some of these lesions. So if you look at the left panel, you see what normal looks like on the venous side, and then you see this extensive webbing and scarring that's contracted and irregular as we go towards the right of the screen, where the vessel becomes more fibrotic and you start to develop obstruction of flow on the venous side. So it gives you also a lot of value as far as guiding sizing, as we know and we've heard throughout the day about how to size these vessels, and I think the following lecture will focus on that topic, on sizing and on the deep venous side. But really being able to evaluate the degree of stenosis and then sizing the vessel appropriately becomes critically important, and I'll show you a case example where things can go wrong when you size inappropriately. So as far as iliac vein compression, there's several different types of iliac vein compression. I think most people are familiar with Matherner syndrome, which traditionally is the left common iliac artery—the right common iliac artery compressing the left common iliac vein, and that was described as the Matherner syndrome. But what we do know now is that compression can happen at a variety of different places. It can be on the right side, it can be on the distal right side, and again, I'll show you some examples where you can go wrong if you're not properly assessing these vessels and again, venography alone isn't enough. And so this is the classic Matherner syndrome. This is a patient that we did that we actually published, and I'll show you why it was published, but you see here just a routine compression on the left side in the left common iliac vein that is the classic Matherner syndrome. And the arrows point to the arterial side. He actually has arterial stents on that side as well, and it shows you where that right common iliac artery goes over that left common iliac vein. Obviously, the ultrasound is what demonstrates the degree of compression. In this particular case, the venography shows that very well, but you can see the complete compression and the slit-like opening in the common iliac vein on ivis in these cases where there's compression. But what was interesting for this particular patient was that this patient had right iliac vein compression as well. And for academic purposes, we actually ended up doing a simultaneous arteriogram as well to demonstrate how that compression occurs. And so this shows the internal iliac artery from the right side coursing around the right external iliac vein, and it shows you exactly why you can have compression in other locations as well. This particular patient had a calcified nodule from that arterial side causing the compression on the venous side. And so this was easily fixed with stents. We have dedicated venous stents now, and we got a great result. But what it comes down to is if you don't add intravascular ultrasound to the plan of treating these patients, you can go wrong really easily. And how do you accommodate or integrate intravascular ultrasound into these deep venous interventions? So this is a great paper by Dr. Gagne, Paul Gagne and colleagues, and this is the video trial that actually looked at venography versus intravascular ultrasound for specifically this purpose, for iliofemoral vein obstruction. And talking about algorithms, we discussed that, making it algorithmic in your practice. Here is an algorithm that they used in the video trial. And so perform the venogram, you know, perform IVUS, and so your decision is not made just on the venogram. In this particular study, you know, they compared the decisions made from the venogram versus the decisions made from IVUS. But then there's a post-IVUS as well, because if you don't do the IVUS run following the intervention, you may miss things in the intervention. And so it's really important. And so if you look at this from the video trial, if you look at this data, this graph, you'll see that that bottom right, that shaded area, shows that IVUS detected greater than 50% stenosis, but the venogram demonstrated as less than 50% stenosis. And so this is the difference between intervention versus non-intervention. And so you can go way wrong if you're not utilizing intravascular ultrasound. And so if you look at this chart as well, if you look at that mean stenosis by diameter and venogram versus IVUS, there's almost a 47% stenosis to 62% stenosis, you know, change with the utility of intravascular ultrasound. So the conclusion of this paper, as expected, was that IVUS is more sensitive for assessing these lesions in the iliofemoral space. But we know that utilization is subpar. So we talked about peripheral arterial intervention, and this is a paper published by Dr. Sosemski and Dr. Parikh. And so we know that on the arterial side, it's painfully low as far as adoption of IVUS. And there are differences between specialties. But for the sake of time, I'm just going to focus on the venous interventions. And we're doing pretty good as cardiologists as far as being above 80%. But I would argue that we need to be at 100% for these deep venous interventions. And so we're still short of where we need to be. But then you also see differences across specialties. So education and learning how to utilize this technology that we have in our hands is extremely important. And why is this important? Well, I'll demonstrate it with a case. So this is a paper that we published on delayed venous stent migration case, which was a patient that presented to our hospital with a PE. And so we got a routine CT PE protocol. And what we found was this radiopaque object sitting in that right pulmonary artery. And it turns out it's a stent. This patient had a popliteal stent reportedly done at an outside hospital. Not sure why, but clearly not sized appropriately. And it completely embolized. And so this was our fluoroscopy image showing that stent lodged in the distal right pulmonary artery. We did this angiogram showing exactly where that is. There was some clot associated with it, obviously. We were able to take a big sheath and get a gooseneck snare. Thankfully, you know, the proximal end of that stent was sitting freely in the main pulmonary artery. And so we could get that snare around it and drag it into our large sheath from the femoral axis. And we completely externalized this embolized stent. And so, again, these are the complications that can happen with stent embolization because you're not utilizing appropriate sizing with intravascular ultrasound.

angiography

intravascular ultrasound

deep venous interventions

venography

iliac vein compression