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Melanie Cole, MS (Host): Welcome to UAB MedCast. I'm Melanie Cole. Joining me to discuss thoracic aortic aneurysms is Dr. Kyle Eudailey. He's an assistant professor and a cardiothoracic surgeon with expertise in complex aortic surgery at UAB Medicine. Dr. Eudailey. Thank you so much for joining us again. So let's start with the definition of thoracic aneurysm. How has your knowledge evolved in this area? What had been thought previously regarding these? Tell us a little bit about them and their prevalence.

Dr. Kyle Eudailey: Sure. First off, thanks for having me back. Melanie, it's always a pleasure. I appreciate it. You know, aneurysms I guess the easiest way to start is to define this a little bit. Aneurysms are really just any dilation of a blood vessel in the body. When we say thoracic aortic aneurysms, we're simply referring to aneurysms that are in the thoracic cavity. So really that's anywhere from the neck down to the torso. The reason that's important is that just happens to be where the largest blood vessels in your body lie, the aorta, which is the largest blood vessel in the body comes out of the heart.

Makes a turn, blood vessels come off to the head and then makes another turn and goes down to the rest of the body. So aneurysms in this particular area are large. And because of that, they have significant consequences if the aneurysms progress to pathologic aneurysms or haven't forbid have some complication of rupture or tear. In terms of where have we come in terms of our knowledge? It's really it's a great question. I would say a long way, but there's still a lot that we don't know.

The easiest way to probably start off is to really define what we do know, which is really the basic physics of aneurysms. So the aorta is, the simplest way to think about it is the aorta is built like a three ply garden hose honestly, it's got intima, media, and adventitious, these three layers and those three layers really give it its strength. And I say garden hose, but maybe that's a really a little bit of a poor definition of how to describe the aorta.

The reality is it's a pretty dynamic structure that is able to accept the blood from when it injects the heart and able kind of move it through the body. But that being said, the order still is subject to the laws of physics, which really this is where a lot of our thinking on aneurysms comes down to and The probably most fundamental important law is [inaudible]'s law of physics, which is the tension in a vessel is equal to the pressure times the radius.

All right. And that's, I'm gonna say it again because it's really. I wish I could draw it out, but unfortunately we're on a podcast, but the wall tension of a vessel is equal to the pressure times of the radius, which basically means that as the radius increases or as the pressure increases the strain on the wall of the aorta increases. And what that means is that the aortic gets kind of strained or pushed by two main things. And one is diameter and the other is pressure.

Blood pressure is the pressure that we're talking about and diameter is really the aneurysm in what we're talking about. And that's the most fundamental basics of how we understand aneurysms.

Melanie Cole, MS (Host): Wow. You're an excellent educator. I was picturing it the whole time. And even before you mentioned blood pressure, I was assuming that's one of the factors that plays a role in these formations. I'd like you to speak a little bit about the hemodynamic factors that play a role in the formation of these type of aneurysms and what you see most commonly as the clinical presentation.

Dr. Kyle Eudailey: Sure. So, unfortunately there are a lot of factors I guess, is what would play into these? The trouble with aneurysms are actually that most of 'em are asymptomatic. And so I really can't say that we see a ton of symptomatic aneurysms. In fact, if you have a symptomatic aneurysm, meaning you either have pain or it has ruptured or dissected, that's just bad news. These people, you know something terrible's happened, it's tearing chest pain, tearing back pain. There's no way that you would know to get to a hospital.

So, in those senses, those are aneurysms that understanding them is less important because people they get kind of rushed to treatment. So the nuance of aneurysms is really understanding how do we mitigate risk of asymptomatic aneurysms? Because the vast majority of aneurysms are asymptom. And so ultimately what we're trying to figure out is, where is this line between the risk of continued surveillance? Meaning we know that there's an aneurysm there and We just keep watching it versus the risk of surgery.

And so what's really important. And this is really another big, important concept is understanding this sort of risk of surveillance versus risk of surgery balance. And so I often talk to patients about, if we have an aneurysm and we know it's there, we know a bunch of factors that sort of allow us to assess the risk of the aneurysm. And when that risk starts to increase, eventually we say, all right the treatment modality, which is surgery, either open or endovascular, is lower than the risk of watching the aneurysm.

Because we know that it's certain sizes the risk of the aneurysm is significant in terms of its risk of rupture or tearing. And so this again gets back to sort of the fundamentals of physics and this actually gets back to some in the lab testing and out of the lab testing of the actual mechanical properties of the aorta. We know that if you have a vessel that is roughly six centimeters or 60 millimeters, there's significant increase rigidity of the tissue. There's decreased extensibility.

And at that radius, if you apply a pressure of 200 millimeters of mercury, which is what we see sometimes if people have kind of wildly outta control, blood pressure, you basically exceed the tensile strength of the aortic tissue. Now there's a lot of things that play into the tensile strength of the aortic tissue, meaning. Not all aortic tissues kind of created equal and I'll kind of walk through some of that, but that's the real kind of fundamental rub is that risk of surgery versus risk of surveillance.

And so the question of how do we assess that risk of surveillance? There's a sort of a list of things that we can kind of go through which is what I go through with my patients. And that's based on several factors. And so the biggest ones are diameter, which we already touched upon, which kind of goes back to that LA Plaza's law. Location, meaning specifically where it is in the body, the expansion rate meaning how fast it's expanding, whether or not there's some associated family history that would kind of put you at higher risk.

Meaning that something else might be going on besides the size of the aorta and then the other is presence of an associated disease. Meaning is there some other factor besides the aneurysm that we need to weigh in and that usually has something to do with valve disease or heart disease or is there some other associated etiology and these are mostly genetic factors connective tissue disorders, familial thoracic aneurysm disease, or Cusip of valve disease.

Melanie Cole, MS (Host): before we get into treatment options, is there screening? Do you see this coming as a future process? And some of these are found incidentally and there are certain risk factors you've mentioned, but is there screening, do you think there should be.

Dr. Kyle Eudailey: Well, you know, screening is such a complex question in this day and age, because that gets into the fact of the use of resources. And if you screen everybody with certain scans, you may have false pauses, false negatives, but you might find other things, not necessarily aneurysms. So at present there's not a, at least for thoracic aneurysms, I should say there is not a clear indication for screening other than if you have a family member with a known aneurysm.

So that's kind of the big takeaway, meaning that if you have a family member with a known aneurysm, typically we recommend starting with a noninvasive screening and then moving to Either a CT scan or an MRI. And that's because if you look all across the board, if somebody has an aneurysm, there's roughly a 10% risk of your first order relative might have an aneurysm. Now that's more partly driven by the genetic components of aneurysms.

Because outside of the genetic, there's also the environmental factors of aneurysms, meaning risk factors that people sort of expose themselves to regardless. But I would say at this point, there's not a blanket screening statement in terms of who we should be screening. And the reason being again is because a lot of these are asymptomatic and we don't have a pinpoint on who exactly is gonna have it. Other than if we know that there's somebody within the family that has it.

Melanie Cole, MS (Host): So, when do you consider intervention for thoracic aortic aneurysms? Tell us a little bit about whether you're doing endovascular aneurysm repair and how that has helped make it a more reproducible, reliable procedure. How is this performed? Tell us a little bit about what you're doing in these cases.

Dr. Kyle Eudailey: Sure. So I think there's two parts to that, right? The first being when do we consider surgery is probably the most important part. Surgery itself we can get into. But when to kind of pull that trigger for surgery is really nuanced and important. And I guess what I would say to anybody who listens and that's providers or patients, the important aspect is that there are guidelines for when to treat patients with aneurysms, but they are truly guidelines, meaning that these are not the sort of same hard and fash rules that we see in valve disease and coronary disease.

Because every patient's risk is very specific to them. And that's driven not only by their aneurysmal. But also by their surgical risk, because you can imagine if you're treating somebody for an asymptomatic pathology, the surgical risk plays important role. And so it's an interesting aspect of medicine which a lot of aspects or a lot of other areas of medicine have this, but the risk of the intervention needs to be heavily weighed against the risk of treatment. And that has important implications as we move into endovascular procedures, which theoretically might have lower risk to patients.

So what I would say is the the timing of surgery is heavily based upon the individual's risk and the individual's risk gets back to those things that I've mentioned before, which is diameter, location, expansion rate, family history, and associated ideologies or disease. And so kind of walking through those is really how we get into the decision to move forward. Diameters is really kind of the most important one. That's the one that we consider that's what most of the guidelines are based off of.

And that gets back to the physics of what we discussed for ascending aneurysms and arch aneurysms. We typically consider an end diastolic dimension of around 55 millimeters. Again, that gets back to that physics of around six centimeters is where we really lose all Tensile strength or functional strength of the aorta. But 55 millimeters is, it's not hard and fast because not everybody's built the same, meaning some people are shorter, some people are taller. And so we do consider size indexing, which is in some guidelines, but not in others.

And that includes an aortic size index to a body surface area, which is typically anything greater than 2.75 per meter squared. And then we also do height indexing which we have an aortic height index which is typically aortic cross sectional area divided by the height and that's greater than tent. So all of these are kind of used as pseudo sizing measurements. The location is also important. When I say thoracic aortic disease, there are really a couple different spots in the thoracic cavity. One is the aortic root.

That's a little different than the remainder of the aorta, because the valve is closely a part of the structure down there, as well as the coronary arteries. This changes the risk of the operation. If you're addressing root pathology, also it necessitates that you have to address the valve at the same time. The ascending aorta is a little bit more straightforward, but that is the area that is the most dynamic of the ascending order. And also is the area that sees usually the highest strain. And so, that is typically where w e use that 55 millimeter number.

The arch is the, sort of as the aorta turns and then the descending thorac aorta, again, we use 55 millimeters, but that's for endovascular repair. Whereas if we are considering an open repair, we use a slightly higher threshold only because the open repair comes with additional risk getting back to that risk sort of, balance that we talked about. The expansion rate's also important. This is something I always talk to my patients about. Aneurysms typically grow it's somewhere around a millimeter a year, but the best concept to understand is a balloon, right?

When you first blow up a balloon, it's hard to blow up. But then as it gets bigger and bigger, it gets easier and easier to blow up. So as aneurysms grow, the rate of expansion actually increases which is important to understand. So if we see aneurysms that are growing greater than five millimeters a year, that's a soft indication, or a reasonable indication to consider repairing those aneurysms. And then there are the additional factors that would tip us over the edge, which I had sort of mentioned before. Meaning is there high risk family history?

Is there some associated disease, meaning that you're treating the patient for some other valve pathology or coronary disease? If somebody's undergoing open surgery for some other procedure that's indicated, then we actually replace the aorta at 45 millimeters, which is much lower than the 55 millimeters that I had mentioned. And then based on specific genetic genotypes, we can be more aggressive meaning patients with [ inaudible]. .

We are very aggressive about how to repair their aneurysms down to the level of 40 millimeters, whereas patients with standard morfans it's closer to 50 millimeters and patients with Bicussip valve diseases, it's closer to 50 millimeters. The important takeaway of all of that is it's nuanced and it's very patient specific. I guess that answers your when. I haven't crossed over into the how yet you want me to continue with that?

Melanie Cole, MS (Host): Well, yeah, because this is absolutely fascinating. And I thank you for giving us those predictors for successful repair. So why don't you just tell other providers briefly some of those technical aspects Dr. Eudailey, that you look to that really help them to achieve better outcomes, because this is really the main thing, right? You're an expert in this and they're looking for better outcomes for their patients. It's about when to refer, why it's important and why you are such a specialist in this particular situation?

Dr. Kyle Eudailey: Sure. So, you know, I think when for me, I've spent a lot of the last couple years of my career explaining to people that it's not a bad thing to send somebody to a surgeon early only because the big takeaway that I really preach is that just because you're sending somebody to a surgeon doesn't mean they're getting surgery. I find that patients are often much more accepting of when they cross that surgical threshold. If they've know n a year or two years before. And also if they understand the thinking around, when we actually consider surgery.

And so we usually say, really being not on the super conservative side but I typically say, I think it's always reasonable for a surgeon to see somebody when they have a thoracic aneurysm that's greater than 45 millimeters. It doesn't necessarily mean that they're ever gonna need surgery, but somebody does need to take control of the surveillance schedule, meaning driving. How often the aneurysm is imaged and also making sure that the aneurysm is imaged reliably. One of the most important aspects. Understanding thorac aneurysms is reliable imaging.

Meaning that when we talk about diameter, when I talk about those numbers or those surgical thresholds, what's really important is understanding that's a center line measurement, meaning that's a coaxial measurement against the flow of the blood and aorta. The aorta is a dynamic and windy structure. And when we do CT scans, we're typically only looking at it from certain cuts. And so what's really important is that the aorta is measured at a sort of Coplain or coaxial measurement of the flow of the blood, in order to get that diameter.

You can imagine if you take an oblong cut of the aorta, you may think that it's six and a half or 65 millimeters? When the reality is it's only 40. That's an important takeaway because I get a lot of referrals where people think they have a seven centimeter aneurysm, and it's not anywhere near that. Additionally I put in there that I had mentioned that the expansion rates and indication for surgery, the trouble is if you have two scans that were done without the same precision and without the same way of measuring somebody may say, oh, I see in the chart that you had an aneurysm this size.

And then they look and they take kind of a sloppy measurement. And they think that the aneurysms grown 10 millimeters in the span of six months it's important to understand how to measure and what to be looking at and to have somebody who's kind of the reliable predictor of where these are being measured. And that's one of the crux of understanding how to refer a patient and also understanding then how they end up to that, when we decide about surgery.

And I'll make a note, in regards to imaging, not all imaging is created equal. Some CT scanners take better cuts. Additionally, if you're dealing with an aortic root aneurysm, the aortic root and the Aascending aorta are particularly dynamic. I'd mentioned that the size that we consider is the end diastolic dimension, which is the largest size of the aorta. And what that means is that the aorta can actually have a 10 to 15% variation just within the cardiac cycle based upon whether or not you catch the aorta at the right time of the cardiac cycle.

So when you're talking about millimeters in deciding between surgery for somebody, these are the nuances that you need to consider before you take 'em to the operating room, because surgery for an asymptomatic disease, it's important to understand when to pull the trigger in and when it's worth it for a patient.

Melanie Cole, MS (Host): And isn't that the key takeaway you are brilliant. Dr. Eudailey, what an informative educational podcast. I was literally riveted. Thank you so much for joining us today and really explaining all those important predictors. When you're talking about thoracic aortic aneurysm.

Dr. Kyle Eudailey: Can I make a plug for one more thing?

Melanie Cole, MS (Host): Please do.

Dr. Kyle Eudailey: The other aspect that I don't think people understand is when you have an aneurysm, there is actually some element of patient education, which needs to happen. And that patient education, it comes down to a few things, because this is the one question I get a lot, which is, am I a time bomb? Am I gonna explode? Right. And simply educating a patient on their risk is really important. Meaning what can they do? Do they have to walk around on eggshells? Because the reality is most people don't have to walk around on eggshells.

The most important things that we can consider is providers are reduction of cardiovascular risk, which really means making sure that your on appropriate blood pressure medications, making sure that the blood pressure's well controlled. Usually we typically like to go anti impulse therapy, beta blockers, or an ACE or an ARB as these are kind of the best modalities for after load reduction. The other is smoking cessation, which in and of itself is associated with aneurysm formation, aneurysm expansion, aneurysm rupture and then the other is.

You know, discussing with people, exercise and activity. I usually tell people you're free for aerobic exercise run jog. I want you to do lightweights, increased reps. The big things are to avoid extreme, heavy lifting, which we usually about half your weight.

Melanie Cole, MS (Host): Vasalva Maneuvers.

Dr. Kyle Eudailey: Exactly. Avoid sustainde vasalva maneuvers. But the important thing is that exercise is good. And so often I get people coming in and they're, you know, they're beside themselves cuz they think they're gonna explode at any point. And so it's really important to sort of understand and talk to people about understanding what their aneurysm means. And I think that's probably the most important aspect of what I do in terms of when I see people that, and this is also a final sort of PSA announcement, but we've also found that a set of antibiotics which are called fluroquinolone antibiotics most specifically levoquin and Cipro.

If you have a known ascending or root aneurysm, if you take prolonged courses of antibiotics, you have increased risk of an aortic event. And that's new information that just came out from the FDA and there's a black box warning on those only as recently as 2018, but it's not as if an individual's allergic to those, but if they take prolonged courses, they can increase their risk. So simple things like blood pressure control, avoiding the wrong antibiotics and then making sure that you exercise, but just don't strain that can go a long way.

Melanie Cole, MS (Host): And patient education. Wow. Thank you again, Dr. Eudailey. A physician can refer a patient to UAB Medicine by calling the MIST Line at 1-800-UAB-MIST or by visiting our website at UABmedicine.org/physician. That concludes this episode of UAB MedCast. I'm Melanie Cole.