 today I'm going to be talking a little bit about aortic stenosis and this is going to be a pretty heavy technical talk so pour a nice glass of coffee and it'll help you get through this. So he's a 59-year-old male who presents to his family doctor with recurrent chest pain and lightness, has a pacifical history of diabetes, hypertension, hyperlipidemia, goes to the hospital, gets several investigations done and it's found out that he has aortic stenosis. So the first part of diagnosis of aortic stenosis is morphological. So in this picture's videos here you have a short axis aortic valve on the left hand side and the right hand side you have a color comparator. It's neat to note here that actually the effect of killer comparator has on your on your frame rate. It drops from 103, but it's all the way down to 29. So when you're doing the morphological insemination of aortic stenosis you're basically looking at four things. You're looking at the number of leaflets, the mobility of the leaflets, the thickness and the calcification. One, based on the two major types of triplacid aortic stenosis would be calcific and rheumatic. So how do you tell the difference between those two? Well it's quite, oops sir, it's quite easy. Rheumatic disease is typically evolving the commissures and you end up having a triangular orifice. While the calcific disease you have calcification at the basis and in the central parts and and consequently you get more of a stelae orifice. The other thing that's a little hint if you have rheumatic versus calcific disease is that with rheumatic disease you typically have a mitral valve involvement. Another concept you read about a lot of times is aortic sclerosis. I actually really didn't know what that entirely meant, but the definition of aortic sclerosis is a calcified thickened valve with normal leaflet motion and typically at velocities less than 2.5 meters per second. So continuing on to this example and back to that previous image. So what does this valve look like? Is rheumatic is a calcific? Well from my appearance it looks like it has three leaflets. They're not moving very well and it kind of it's hard to appreciate here. It looks more like a stelae like appearance. So this is a calcific disease and if we went and looked a little bit further there's no good common in mitral valve disease. So continuing on with the investigations this is a short axis I mean long axis aortic valve again with color compare and what you see is a heavily calcified valve and again you'll see some shadowing distal to the aortic valve or a deeper than the aortic valve and then there's a little bit of AI probably mild AI and I'm not going to go into that because we had three talks on AI already today. Continuing on on the left hand side it's a lv. It's thickened it's contracting nicely probably grade one lv. We did diastole genus we probably have a least impaired diastolic dysfunction and on the right hand side there's a double envelope conuti equation performed and we come up with a pretty significant aortic stenosis around 0.46 square. So for the next part of this talk I'm going to talk more about grading the severity of the aortic stenosis. So you morphologically it looks like yes but now how severe is the anus? So the guidelines break there's a nice table of the 2017 guidelines breaking down how to grade anus there are in the tables divided in yellow part section and green section and a blue section and we're going to focus on the yellow section and that's our recommendations for Doppler for all patients with AS. I'm going to talk about one of the reasonable ones later on in the talk so keep that in mind. So again there's and you can look at assessed age as jet velocity mean gradients and the conute equation by area. So let's start with the first AS jet velocity. So what is the what is the best jet velocity obtained? Well according to the guidelines it's the highest velocity signal obtained from any window. Again this is typically going to be obtained in your deep transcaster view. The main components of this are you basically want to optimize your window you want to make it as large as possible increase your y-axis use gray scale. One thing people make a mistake about many times is picking up these fine linear lines at the apex of the curve or the peak of the curve you want to eliminate those those fine linear signals. You need to make sure your Doppler is parallel to the intercept angle and that's basically based on the Doppler equation with your cosine theta. If you are under 15 degrees you're probably okay it's probably going to result in an error less than 5% or underestimate of your peak velocity through the order problem. If you have a situation where you have any irregular rhythm such as atrial population which is pretty prominent with patients with chronic neural stenosis then you want to look at several cycles and the guidelines recommend five. But again you're going to still pick your highest peak velocity from any of these windows. Continuing on like we talked about velocities you can also look at mean gradients. So again gradients are calculated from the velocity information but peak gradient is not really it's not obtained similar in the same manner as mean gradients. So peak velocity is basically equivalent to the peak gradients 4v squared per the Bernoulli's equation. Mean velocity you can't be graded you cannot calculate from the mean velocity that you obtain from the from the mean velocity. What you the actual machine actually does is averages the instantaneous gradients across the ejection period and again applies the simplified Bernoulli's equation. You need to keep in mind that the Bernoulli's the simplified Bernoulli's equation is not valid if your velocities through the order valve are less than 3 meters per second or more particular in our populations when the velocities are are greater than 1.5 meters per second through the LVOT. And again it's as if for example if you have a velocity of 2 through the LVOT 2 times 2 square times 4 is 16. So that's going to have a huge effect on your pressure gradient. So if that's the case then you probably can't use gradients like I guess it's a case where you'd have a high LVOT gradient would be a patient with suba or stenosis. So if you have a patient with suba or stenosis with a high gradient or a high velocity through the LVOT then you can't use your mean gradients and at that point there the best option would be to do telemetry of the valve. So continue on with mean gradients. This these two images confused me for a long time but reality is echo overestimates the gradients with cath and it does this by two ways. With traditional cath one would calculate the peak to peak gradient and how they how does the cardiologist do that they put a catheter into the LV the measure gradient pull that through the aortic valve into the aura measure that gradient and subtract and that will give you a peak to peak gradients. Initially with a technology they would do that at different time time frames because you can't measure both at the same time. New and more advanced catheters they actually measure at the same time because it has two offices one in the LV and one in the aura. And actually after talking to Dr. Austin a bit about this he says that the peak to peak gradient when it's measured at the same time at both locations actually very similar to your mean gradients. Looking at pressure recovery again I get a complicated issue but what happens is when you have a blood volume going through the LVOT you have a high potential energy and low kinetic energy or low glossies. As you go through the aortic valve your glossies increasing your potential energy decreases and as you exit the office it occurs. However as you exit you lose some of the energy via heat and this is more pronounced in patients with and this is the heat loss is more pronounced in turbulent flow which occurs in patients with large aortic. So the net so basically in a patient with a small aorta there's less laminar flow there's more pressure recovery and at the net result is that echo over estimates gradients. Again there's like all my references those references are actually pretty good at reviewing these concepts in further detail. Continuing on to the last component of assessing the severity of AS is the cotton unit equation. We're all pretty familiar about this but basically you calculate the stroke volume in the LVOT. If you get the peak AV VTI you can solve for AVA and there's several assumptions when you use the cotton equation and I'm going to go through some of these assumptions that make this more challenging. So the first question is what assumption in the cotton unit equation results in the greatest error? So again I'm probably giving away this answer in the test at the end but the cross-sectional area of the LVOT is the most challenging measurement for the cotton unit equation. This is a study looking to compare in 2D versus 3D with diameters and also doing direct measurements of the 3D area using telemetry. And what you can see here is small changes in your radius has quite a big effect on your aortic valve area. In the top one you have classical severe AS and with a modification of that you can put it into more of the moderate range. Though it actually is fairly similar at that point. The reason why the LVOT is very sensitive it's fairly obvious but you square the radius. So that is one of the major sensitivities of with the LVOT measurement. The other sensitivity is the assumption that the LVOT is a cylinder. And as you can see in the diagram C the LVOT has a minor and a major axis. The minor axis is an AP axis while the major axis is a medial lateral. So it's more of a elliptical shape rather than a cylinder. And if you apply the assumption that pi r square which is a circle this is going to lead to some error. So they actually recommend now if you can obtain it is to do a 3D plenitry of the LVOT area to try to minimize that error and to improve reproducibility between observers. Moving on I think this actually was brought up earlier in the talk is where is the correct place to place the sample volume of the LVOT. What the guidelines recommend is that you put your pulse wave Doppler at the aortic valve orifice and slowly pull it backwards towards the LVOT. And then you pick the curve with minimal brautting and a closing click of the valve. If you're too close to the AV valve you're going to have an overestimate of the peak velocity. And again if you're too far away you're going to have an underestimate. It's also a little bit challenging. You want to do a place your sample volume at the exact same level where you measured your LVOT area. So you have to keep that in mind when I try to keep that as close as possible. Moving on other limitations of the continuity equation you can failure to obtain your peak velocity. We again we already talked that cosine theta will really under change abrupt large angles from parallel will cause underestimate of your velocities. But then you throw it into the equation then you're swearing it so the error becomes more pronounced. Differential flows. So in reality for the orycinosis the major problem would be pair members VSTs. Thankfully that's not very common. But what happens here is that you measure your VTI and the or your stroke volume and your LVOT. And some of the stroke volume leads through the pair members member VST. In the other one the rest of it travels through the orycinol. And because you lose some of that mass you get over an estimate of the ABA. Another common problem with the con equation is you measure the raw Doppler signal. When you're in the deep trans gaster view you have flow from the mitral. If you have regurgitation you'll have flow directed towards the the aquaprope and then you have your AS jet. And they could be they could be mistaken. The best way to do that is to look at diastology and systology and use your isovalentic contraction time and your isovalent relaxing time to your advantage to help distinguish between the two jets. So you plug in and measure the most appropriate envelope. Two more of limitations would be a low cardiac open state. And what happens here is you have a non-anatomically non-stonotic valve. But because of low flow the valve can open fully. So that leads to and affects your effective orifice area that you calculate through the cognitive equation. And last but not least is prosthetic valves can cause underestimate underestimate of the EAL. And you should basically reference your results with the manufacturer normal values. So we'll continue on with the the presentation. So this is post op. And what you see here in a post op images is a arthrocytic valve. What you're looking for is rocking. You want to make sure the valve is well seated. You want to look for transvalvator and parabola release. And again this all looks very normal. Looking at long axis again you're seeing the same thing. So there's no leaks and there's no and everything appears to be open and closing well. And to finish off the investigations post op you want to do a gradient through the valve. Actually by these my presentation I can't see the side of it but I think the mean gradient is forward but I am going by memory here. But again it's a normal gradient across the bottom prosthetic valve. So we're going to move on to case number two. I can't feel my face when I'm with you but I love it by the weekends. And it's basically a 30 year old male resents to the emergency department with symptoms of left facial numbness and slurred speech. Similar to the last gentleman, a pathological history of diabetes, hypertension and this gentleman has palpitations. Again goes to the hospital TGH gets a million tests and he's found to have a oresthenosis poor LV function in atrial fibrillation. This is his first pre op image of his LV. So it's a pretty poor LV function. We graded it at a grade three LV. Some LVH and some dilatation. Probably significant dilatation. Going into the long axis of the aortic valve. This kind of looks kind of weird. It's very heavily calcified. It appears to be stenotic and there's a high jet velocity exiting the aortic valve. So this is suspicious. Could this be like hospital valve? We'll continue on. So now we're looking at the aortic valve in short axis. And this is a very, again, very tight valve. And again, does anybody know what kind of valve this is? Again, so hard with the interaction here. But this would be what Omron talked about earlier in his presentation. This is a unique hospital valve. Extremely rare. Both 5% of the patients who come into the aurora would have that if they have AS. But in the population, it's closer to 0.02%. And again, it can have one commissure. It could be eight commissure. And again, people with a unique hospital valve typically present early life with a aortic stenosis. And it's also associated with dilatation of the earlobe. Then going on to the right hand side, we see some pressure gradients. We see a peak gradient of 40. And if you trace that curve out, you get a mean gradient of 20. So we have a bad LV. We have something here stenotic, but we might have a mean gradient of 20. So that doesn't fit the idea that this patient has severe AS. So this is when you have to go back to the guidelines. This is probably more advanced than we need to get into, because we're a perioperative echocardiographers. We usually see our patients in the aurora. And hopefully, this has been determined before we come into aurora. And a matter of fact, in order to do the final steps of this algorithm or this approach, you need to do a dopamine echo, which again, we would not do in the operating. So basically, to summarize this grading of AS, there's basically two columns. I'm going to move through it quickly. You have a typical high gradient of AS with a peak, a mean gradient greater than 40, a peak velocity greater than four. And the only thing you need to exclude is whether this is a high flow status. Examples of that would be anemia hyperthyroidism. And what they recommend the guidelines is fix it and then reassess. And then if you're going on to the left hand side, this is your low gradient AS with a gradient less than 40, or mean gradient less than 40, which is what we were I was showing in the previous slide. You look at the ADA by the continuity equation, calculate or a preliminary, calculate that area. And then you keep on falling your way down the algorithm. If you get to a point where you have a low EF, which is around step six, then you do a dopamine study. And if the dopamine study causes your area to increase over one, you have pseudo, if it stays under one, you have truce of your stenosis. This is the only aspect of the assessment of your stenosis that doesn't use echo. I kind of alluded to have mentioned before, but the assessment of your stenosis is now an entirely echo-based assessment rather than other modalities. The only exception would be the calcium score by CT, which is used to integrate it to be able to help delineate some classifications of ADS. I'm going to skip this slide, but it's basically summarizing what I just did before using the dopamine stress test. And the last part of the talk is how many gradients or velocity measurements needed to be made, a need to be averaged with atrial fibrillation. The guidelines recommend five averaging of the, of the velocity gradients. One, because you get beat to beat variation, so your loading conditions are going to change beat to beat to beat. So that's going to have a profound effect on your, on your continuity equation. One other way to get around that would be to do a double envelope, which I'm showing in the middle here. If you do a double envelope, you're actually capturing your, your velocities at the same time at the same beat. So that would limit some of your beat to beat variability. And you can actually just directly apply that to the velocity ratio. I think Azad spoke about that earlier. And if you have a, I think Azad did or maybe not, but if you have a velocity ratio of less than 0.25, that'd be indicative of severe AS. And just to finish off the images, this is post-op. So the gentleman went underwind of our platonic valve, again, similar to what we talked about before, a good function. All leaflets are working. On these images, there's no leak. There's a lot of acoustic shadow beneath the valve. And this is our deep trans-scaster view. There is a little leak. This is probably a normal jet with the mechanical valve. And we get a nice mean gradient of four. So again, another successful story or successful valve replacement. And that ends my presentation. Thank you for your attention.