 Hello everyone! So, today we are going to be talking about the hemodynamic calculations that we can actually obtain using transesophageal echocardiography. This is part of the lectures for the Toronto General Hospital cardiac fellows as a preparation for the PT Advanced Exam of the National Board of Echocardiography. So, let's just start. I don't have any disclosures to discuss with you. As you well know, there is no academic or financial or any kind of compensation received for giving this talk. The objective for the talk that we are talking today is going to make a little assessment of what can we do with Doppler equation, Bernoulli equation, how to get all or the most common intracardial pressures using TE. The continuity equation, how to assess intracardial actions, TPDT, what it is, what do we use it for and we are going to talk a little bit of systemic and pulmonary vascular resistance. So, I thought interesting to get this little table so you guys can have like a little preparation for your exam. There is a summary of almost every single calculation that you can actually think about. Those are the most frequent kind of calculations that you're going to be using when you are doing a study in TE and you can actually use it as a summary at the very end, okay. Some of the formulas are not recommended by the American Society of Ethical Guidelines. Some of them are actually extracted from different papers where they find like really good sensitivity and specificity when they are used. So, let's just begin with the hard material. So, to start with, we are going to be talking about the Doppler equation. Remember, the Doppler equation is just like a representation of the Doppler effect. And when the Doppler effect, when the source and the receiver are in motion relative to each other, this Doppler effect is presented as a Doppler shift, which is what we are seeing as the first part of the equation, okay. So, when the sound that is emitted moves towards the transducer, so this is going to be a positive effect. And then when the wavelength is actually moving away from the transducer, we are going to call this negative, okay. So, the blood flow, which means that the blood flow which is moving towards the transducer produces a positive Doppler shift signal. And conversely, the blood flow that is moving away from the transducer produces a negative Doppler shift signal. So, it's important from the Doppler equation that you remember what is what is FR, which is the reflected frequency, which is FT, which is the transmitted frequency, and this is going to be given by the transducer. The number 2 represents a constant and it reflects the signal of moving to a target and coming back. V is going to be the velocity of the blood in meters per second. Causing of the angle is the angle of isonation. So, with that, the maximum recommended angle where you are assessing a signal is 25 degrees. And what's that? Because the cosine of 25 is 0.9. The cosine of actually 0 degrees is 1, which means like a perfect signal back. So, ideally you are looking for zero angle when you are measuring a signal by the Doppler equation. But up to 25 degrees is acceptable because the cosine of 25 is going to be 0.9. The moment that you start to actually increase, if you go to 90 degrees, you are not going to be able to get any Doppler signal back because the cosine of 90 is going to be 0. So, the question is completely worthless, okay? And finally, all this equation is divided by C, which represents the speed of sound in soft tissue. So, the most common way of actually represent that is 1.54 meters per second. But it can actually be called 1540 meters per second to the minus one. So, to begin going, you probably are more familiar with how to calculate pressure gradients and to calculate the pressure gradients by Te, you are going to need the Bernoulli equation. We tend to simplify this equation, but really the Bernoulli equation is just like a pressure gradient that is calculated from the velocity using that equation, okay? So, what is going to be component of the Bernoulli equation is going to be the convective acceleration that is the one that we are going to be able to change for parameter-wise, the flow acceleration and the viscous friction. Both the flow acceleration and the viscous friction are going to be negligible for the equation, because we are going to consider them equal in all the in almost all the circumstances and we will talk about which ones are the exceptions for that, okay? It's important to differentiate when we are actually talking about the Bernoulli equation that the difference in one point towards another is reflected by 4 per V to the square, which is what we got. So, from these formulas and having an account what I just mentioned you are going to have to simplify Bernoulli equation, which is your well-known the difference in pressure is going to be measured by the pressure gradients are going to be measured by 4 per V to the square and this is going to give you based on your max velocity your peak gradient from the V max. But, there is an exception to that. You can actually not use a simplified Bernoulli equation and it's recommended to use the modified Bernoulli equation in two circumstances. First one is when your V max is low, which means less than 3 meters per second when your V proximal is actually high, more than 1.5 meters per second, high enough to have an impact in the gradients. So, when the velocity is 1 meter per second the V-prox, the velocity the proximal velocity is below 1 meters per second, that gives you almost nothing because it's 4 per 1 to the square, which is 4 millimeters of mercury. So, anything below 1 is actually going to give you an negligible number but if it's more than 1.5 or even if the V max is small this will have an impact on your pressure gradient. So, then is when you guys need to use the Bernoulli equation it's important to realize that the Bernoulli equation is not the one that is going to give you the mean gradients when we are assessing, for example, an aortic stenosis. So, the mean gradients those are an average of the instantaneous mean gradients over the reaction period and this is calculated by the software of the machine by the velocity time integra or the BTI or to get an approximation you can do 2.4 per B max to the square and that will give you like an indirect measurement of what's the mean gradient. Okay, so, we have been talking about the Bernoulli equation so, how do we calculate intracardiac pressures then? So, the first thing that you need to remember is that the velocity of our regurgitan jet is directly related to the pressure drop across above and using that, you can determine any intracardiac pressure so, the different in pressure from one point to the other equals the pressure gradient which equals the Bernoulli equation which is 4B to the square so, I'm going to ask you to follow 3 simple rules if you can't remember those 3 rules you will not need to remember any formula or memorize any formula you will be able to deduct the formula from the 3 rules that I'm going to show you now so, to start with identify which is the regurgitan jet and if it's on the right or the left side of the heart so, if it's on the right left, the time of the regurgitan jet is going to be different and to understand that means if you are having on the right side of the heart a regurgitan jet during cistory this is going to be your tachaspid regurgitation if you are having a diastolic regurgitan jet from the left side of the heart then, we are going to talk about our regurgitation same thing for MR and PR so, you need to realize if it's on the right side of the heart the pressure that they are asking you or if it's on the left side of the heart and you need to realize if the pressure that they are asking you is during cistory or during diastory and based on that, you are going to know from which regurgitan jet you are going to be able to obtain the formula ok and the last of the things, one you know if it's from a right pressure or a left pressure, the one that you are asking you are a cistolic or a diastolic pressure you need to identify between which two areas the pressure difference is occurring that's very simple, you only need to flow the regurgitan flow so from chamber A to chamber B where the regurgitan jet goes, which is the different in pressure gradients, ok so let's just practice a little bit that, ok, so you have the right ventricular pressure so you want to know for example the RBSP the right ventricular cistolic pressure we are talking about a pressure on the right side of the heart during cistory which is the regurgitan jet that happens on the right side of the heart during cistory, ticaspid regurgitation yes so and the flow goes from the right ventricone to the right atrium when, in cistory so the right ventricular cistolic pressure during cistory and the right atrial pressure during cistory so if you take that your RBSPs of right ventricular cistolic pressure are going to equal the pulmonary artery cistolic pressure ok and on the right atrium the pressure during cistory is going to be your right atrial pressure or CBP there is an exception to that the right ventricular cistolic pressure is not only going to equal the pulmonary artery cistolic pressure if there is pulmonary stenosis you need to subtract the pulmonary stenosis gradient between the right ventricole and the PA otherwise the formula is not going to be accurate just have that in mind ok, so based on that we apply the pernually accretion and then what we got is that the pressure gradients equal 4V to the square in this case we mentioned that we are going to use to get the RBSPs is going to be the TR so pressure in the right ventricle RBSPs minus pressure in the right atrium right atrial pressure or CBP equals 4V to the square being the velocity from the TR so RBSPs or pulmonary artery cistolic pressure this is going to equal 4 for the velocity of the TR to the square plus the right atrial pressure and as you well know you will localize your modified by K-valve view in TE get the TR yet to a continuous width doctor from this modified by K-valve get the maximum velocity on the TR square it, multiply it before and add the right atrial pressure and you will instantaneously get the right ventricle cistolic pressure you need to remember one thing what is going to happen when you have TACASPIC recogitation and you have a PDA or a BSD we will talk about that later on the lecture but choose remember that because then the things are going to be different and remember this RBSP is not going to be reliable with RV failure RV infarction and RV obstruction those three conditions are not going to validate this formula just have it in the back of your mind so we have been talking about right ventricular pressure what about pulmonary artery pressures ok, so let's see that we want to know pulmonary artery mean pressure or pulmonary end diastolic pressure so if you want to know that we are talking about a right sided pressure that happens in diastole so which is the regurgitation yet that happens in diastole in the right side of the heart pulmonary regurgitation so we are going to use the pulmonary regurgitation flow and the flow goes from the PA to the RV so the pressure in the pulmonary artery during diastole can be the pulmonary artery the pulmonary artery mean pressure or the pulmonary artery and diastolic pressure and the pressure in the right ventricle during diastole means that the tricuspid is open so the RVDP is going to equal the right atrial pressure because the tricuspid is open and is communicated with the right atrium so we can assume the RV RVDP is going to be your CVP at that time so using the formula we start again from the PA pulmonary artery pressure during diastole minus the RVDP which is the right atrial pressure will equal 4 per V to the square in this velocity from the PR jet so from all this if you want to calculate the pulmonary artery mean pressure what you are going to get is 4 per V to the square because it is the mean pressure the PR peak velocity as you can see in the lower part of the screen on the right side the PR peak pressure there is a gujitan you get that and automatically you will get the mean PA pressure and you need to add to that the right atrial pressure another way of determining the pulmonary artery mean pressure is another formula that we normally is not related to the Bernoulli equation which is a third pulmonary systolic pressure plus two-thirds of the pulmonary artery diastolic pressures which is another common formula known for that ok so if we want to go and determine what's the PA end diastolic pressure it's exactly the same formula that we were using it's 4 per the PR but it's an end diastolic velocity which you will measure as you can see in the right side part of the screen in the lower part of the screen the PR end diastolic velocity over there you will take this one as your PR end diastolic velocity you will square that multiplier for another right atrial pressure and that will give you the pulmonary artery and diastolic pressure so what other formulas can we use other articles that talk about the mean different in pressure between the right ventricle and the right atrium plus the right atrial pressure and the other formula that is commonly used in other articles is 79 minus 0.45 per RBOT acceleration time but those are formulas that you need to memorize if you want to remember you can always go to the articles and go back to them and get the formulas but if you want to use your Bernoulli equation using the equations that we just mentioned you're going to be able to perform so we have talked about RVSP's we have talked about diastolic pressure what about left atrial pressure ok so this is the left atrial pressure on the left side of the heart this time during systole the regurgit and jet that happens because during systole is when the mitral ball is supposed to be close and then the left atrial pressure is going to be fully in it so on the left side of the heart during systole the regurgit and jet that happens is mitral regurgitation and the flow in mitral regurgitation goes from the left ventricle to the left atrium so during systole the left atrial pressure during systole is going to equal your systolic blood pressure and the left atrial pressure during systole is the one that we are going to want to calculate so based on the Bernoulli equation again you have left ventricle systolic pressure or systolic blood pressure minus the left atrial pressure is going to equal 4 per B to the regurgit and jet which in this case is the MR to the square so that gives you left atrial pressure equals systolic blood pressure minus 4 per the velocity of the MR to the square ok so this is a classical formula they love to ask this kind of formula in the exam so if you need to calculate that's how you will actually do it so other formulas that have been used for calculate the left atrial pressure that are well known is E from the mitral inflow by put with Doppler at the tip of the mitral leaf let's divide by the E prime by T should Doppler plus 4 or the other one not as well known of 1.24 per E divided by E prime plus 1.9 but again those are formulas that you can actually have in your little you can actually put in your pocket when you are doing the calculations but they are not going to be using the Bernoulli equation to actually detect them so an important part when you are measuring left atrial pressures is like this is going to be invalid when you have an alveotia obstruction a PFO or an ASD and we will talk a little bit about those further on the lecture ok so left atrial pressure left ventricular pressure so you want to calculate the left ventricular pressure ok so you are talking about the left side of the heart during diastole ok the left ventricular pressure during diastole ok this is the the regurgitation yet that is going to happen on the left side of the heart during diastole is averted regurgitation and in averted regurgitation the flow goes from the aorta into the left ventricle so you have flow from the aorta during diastole is the aortic diastolic pressure also known as diastolic block pressure and the left ventricle pressure during diastole is the LVEDP which is the left ventricular and diastolic pressure so based on those two pressures again we get diastolic block pressure minus the left ventricular and diastolic pressure equals 4 per the velocity of the aortic regurgitation yet at end diastole because the left ventricle end diastolic pressure is at end diastole so as you can see here on the right side of the screen the very bottom the AR end diastolic pressure should be measured exactly where the white arrow is indicated and this will give you the left ventricular and diastolic pressure equals the diastolic block pressure that will be given to you minus 4 per the velocity at end diastole of the AR jet to the square so what happen if we have severe and massive aortic regurgitation so you should assume when that happen that the left ventricular and diastolic pressure equals the diastolic block pressure okay this is another exception when we are applying these formulas so we have talk of the 4 most common intracardial pressures that you may be asked for so continuing on we are going to talk about the flow by continuity equation this is something that you are very familiar with from when we assess aortic stenosis again and the continuity equation is only showing that the stroke volume equals area per velocity which means that the stroke volume equals area per in this case the BTI which with the stroke volume we can actually calculate the cardiac output being stroke volume by heart rate okay so when you get stroke volume and we talk about area we are talking assuming that the surface the cross-session area of something the perimeter is going to be the pi per radius to the square and is going to give you centimeters to the square multiply per the velocity time integral of the BTI which is given in centimeters which is the stroke distance this will give you a stroke volume in centimeters to the cube or milliliters okay so stroke volumes in the aortic valve equals the stroke volume in the LVOT so aortic valve area per BTI of the of the aortic valve will equal cross-session area of the LVOT per BTI of the LVOT which is the classical formula that we use to calculate the aortic valve area okay so aortic valve area equals cross-session area of the LVOT which you will be able to calculate from pi per the radius from the diameter in the LVOT to the square okay per BTI on the LVOT from the tracing of the BTI and then the BTI in the aortic valve and then you will be able to calculate the aortic valve area so aortic valve that's the example that we actually place when we were commenting on the continuity equation when you have stenosis you need to remember that what they are going to ask you is the mean gradient and not the peak gradient so you will not use the Bernoulli equation to get the mean gradient the mean gradient is going to be calculated by the machine by the BTI okay but you can use the continuity equation to get the aortic valve area as per the example that we choose comment when we were talking about the continuity equation but what happened we want to actually quantify regurgitation so when you want to quantify regurgitation there are a couple of methods that you can use the volumetric method we are talking about the volumetric measure so we are going to base everything on the regurgitum volume regurgitum volume and regurgitum fraction so in case of aortic regurgitation the regurgitum volume and in any kind of other regurgitation is always going to be equal to the stroke volume of the regurgitum valve minus the stroke volume of the referendum valve in this case the stroke volume of the regurgitum valve is going to be the stroke volume of the aortic valve or stroke volume of the LVOT okay so this is going to be calculated by the cross section area of the LVOT per LVOT BTI and the stroke volume in the reference valve the valve that is normally used is the mitral valve if the mitral valve has no regurgitation or stenosis and this is going to be calculated by the cross section area of the mitral valve per the mitral valve BTI so you all know how to calculate the stroke volume in the LVOT which is going to be diameter of the LVOT and BTI of the LVOT and the people is not so familiar in how to get actually the cross section area of the mitral valve but is familiar on how to get the mitral valve BTI for the cross section area of the mitral valve you will go to the four chamber view get the annulus of the mitral valve you will consider that the diameter and pipe around this to the square you will get the cross section area of the mitral valve and then you will trace the BTI on the mitral valve and you will obtain the stroke volume so when you do the calculations by volumetry you are going to get the volume when you are using the PISA you are going to actually first start to obtain the regurgitum flow and the regurgitum flow in the PISA method is going to be the surface of at the hemisphere so you will shift your baseline towards the regurgitum yet get your 2 pipe per the radius of the PISA envelope to the square per the aliasing velocity which is in T the top aliasing velocity towards the regurgitum yet if we are assessing the art regurgitation from the deep transgaster view and you need to modify that per the angle of the jet divided by 180 with the regurgitum flow the next thing that you need to do is to trace the AR jet by continuous width doper and automatically you will get the peak velocity from the regurgitum jet in the Arctic valve and the BTI of the Arctic valve so the aeroa is going to be your regurgitum flow divided by your peak velocity and the regurgitum volume is going to be affected regurgitum or PISA per AR BTI finally the regurgitum fraction is going to be the regurgitum volume that you already obtained divided by the stroke volume of the regurgitum valve and this is going to give you an estimation okay so what are the pitfalls of the volumetric method so the pulse rate doper sample volume location normally the mitre valve annulus you need to go at the tip of the mitre leaflets and the same thing with the LVOT it can actually be a source of error the other thing is the diameter measurements so any mistakes that is making on the diameter if you are not cutting perfectly aligned the diameter on the location, on the timing so the error is going to be a square which is a very important source of errors you have a radius, you need to average over several bits and if you have a multivalve lesions or shunt the formula starting value if there is a significant shunt it is more than mitre regurgitation of the non-regurgitum valve so we have talked about the Arctic valve let's just talk about the mitre valve ok so stenosis several formulas are described for mitre valve stenosis, the level one class is mitre valve area being the formula 220 divided by the pressure half time this formula is embodied if you have AR because the AR is going to actually provoke an early closure of the mitre valve and it is going to overestimate sorry, it is going to underestimate your mitre valve area ok, so that is one of the formulas it is very commonly used the graphic that you have on the right side of the screen where it is pointing the white arrow shows you that you should not do the pressure half time at the very beginning of the mitre valve inflow and you should wait until the first deflection to actually do the measurement and not take that in account otherwise you are going to do another mistake if you use the continuity equation mitre valve area can be calculated as cross-sectional area of the LVOT per VTI of the LVOT divided by the VTI of the mitre valve exactly as we were doing there with the Arctic valve and there is a third method when you use the PISA method which is 2 pi per radius per square per the alias in velocity divided by the peak which is going to be what is being called the effective regurgitane orifice and there is a nice illustration on the right side of the screen on how to do that but this is to be discussed in another lecture so pitfalls of mitre valve are not just remember when you are using pressure half time you cannot use it with AR or with diastolic dysfunction when you are using the continuity equation you cannot use it with AR or MR but the continuity equation on the difference of the pressure half time is going to be flow independent and when you are using PISA it is flow independent but it is very difficult and it is very susceptible to errors in measurements so when we talk about regurgitation in mitre valve again you can use the bolumetric called the PISA method we already described the PISA method for the or the regurgitation is exactly the same for the mitre for the bolumetric measure on the mitre valve what you want to have is the regurgitan bolum in a mitre regurgitation is going to be the stroke volume of the mitre valve minus the stroke volume of the complement valve which is the LVOT or the RT valve so the stroke volume of the mitre valve can be calculated how do you calculate that the recommendation is to do it and diastolic volume minus ansiastolic volume in the left ventricle which is going to give you the stroke volume in the mitre valve then the regurgitan fraction can be derivated from here ok so we have talked about Bernoulli's continuity equation Doppler effect we want to talk a little bit about intercardiac shunts ok so an intercardiac shunt is measured by the QPQS what is the QPQS so it's a pulmonic to systemic stroke volume ratio which means the stroke volume in the right heart compared to the stroke volume in the left heart ok so how do we measure stroke volume in the right heart you can use it in the PA or in the RVOT which can be cross-sectional area of the PA per VTI of the PA cross-sectional area of the RVOT per VTI of the RVOT as you can see in the image on the right side of the screen the stroke volume in the left side of the heart is the stroke volume in the RVOT or RVOT and again how do you calculate this stroke volume is cross-sectional area of the RVOT per VTI of the RVOT or cross-sectional area of the RVOT per VTI of the RVOT so which is important to know when you are measuring intercardiac shunts is knowing what is the side distance to the shunt inflow and the side distal to the shunt outflow when we are talking about an AASD so the flow goes from the left atrium normally to the right atrium so the distal the side which is distal to the shunt inflow because here the shunt inflow is going to be your right atrium so the side distal to the right atrium is going to be the half speed annulus first then the RVOT then the main PA and the side distal to the shunt outflow, which is the left atrium is going to be the mitral valve annulus the RVOT and the outstanding aorta what happen when you are assessing an AASD normally the flow goes from the higher pressure chamber left ventricle to the right ventricle so the side distal to the shunt inflow is the right ventricle to that you're going to have the RVOT, the main PA, or even the mitral valve annulus. And the site distal to the shunt outflow, which is the left ventricle, is going to be RVOT, astandinaorta, antacaspid valve annulus. For a PDA, which is the connection between the aorta and the pulmonary artery, it's exactly the same principle. So you understand which site is distal to the shunt inflow and the shunt outflow, you actually can calculate using your Bernoulli equation any kind of pressure in ASDs, BSDs, or PDAs. Let's go with examples. So imagine that you have a BSD. It's going from the left ventricle to the right ventricle, okay? And they ask you, you have a patient with a BSD that goes at x meters per second, and then I want you to be able to give me your right ventricular systolic pressure. So what are we going to do? So again, Bernoulli equation, different in pressures for per the velocity of the BSD to the square. What is happening in this velocity, insistently, and is left ventricle to right ventricle? So during systole, the left ventricular pressure, okay, is your systolic blood pressure. During systole, the right ventricular pressure is your RVSPs. So systolic blood pressure minus RVSPs equals 4 per the velocity of the BSD to the square. Then based on that, the RVSPs is going to equal systolic blood pressure minus 4 per the velocity of the BSD to the square. So if in this same question they ask you, how do you calculate the right ventricle and diastolic pressure? So we apply the same formula, and again the same thing. You choose change the timing. Instead of systolic, now we are talking about diastolic. So the right ventricular diastolic pressure is going to equal the left ventricular diastolic pressure minus 4 per the BSD diastolic velocity to the square. What happened with an ISD or a PFO, which is more commonly used? So in a PFO based on the same Bernoulli equation, so you have the left arterial pressure, okay, is actually going to shunt pressure towards the right atrium. So the pressure gradient equals 4 per the velocity of the PFO to the square. Then left arterial pressure, as you can see here, minus right arterial pressure, which is your CVP, is going to equal 4 per the velocity of the PFO to the square, which gives you left arterial pressure equals 4 per the velocity of the PFO to the square plus the right arterial pressure. So we don't care how they want to discuss that. If it's a PDA, it's a PFO, BSD, just based on your pressure gradient equals 4 per B to the square, you're going to be able to determine any pressure that you want. And that's the matter of the flow growth from the left to the right, or it goes from the right to the left. The only thing that you need to change is the subtraction in the order of the flow. Okay, we are arriving at the final of the lecture. I hope you're still there with us. So DPDT. So DPDT is something that we use a lot for quantifying systolic function, and we use it when we have severe regurgitations in the right and the left side of the heart. So the DPDT is the rate of ventricular pressure rise. Okay, so when we start talking about the RB systolic performance, you use DPDT when you have severe TR, for example, because you are assuming that the whole flow on the right ventricle is going forward, when you have severe TR, that's definitely not happening because at least 50% is going backwards. So a good way to actually assess systolic function is the way that the rate of ventricular pressure rise when you are assessing the TR jet from one meter per second to two meters per second, how long it takes to actually rise it. The last time it takes in this rise is going to be actually a better systolic performance, because it's between one and two meters per second. The difference between one and two is going to be always difference in pressures, four per V to the square at two meters per second, which is the V max, minus four per V to the square, which is the V prox at one meter per second, which means 16 minus four. So the DPDT is always going to be 12. And then the DT, the time, is the time, the milliseconds that it's going to take from going from two meters per second, from one meter per second to two meters per second. So if it's less than 400, that means it's a normal. Why? Because it takes a long time to actually be able to generate this regurgitant jet. So the bigger the number is when the millimeters of mercury are going to be higher and the pressure that is able to generate is faster. So based on the same principle, we can assess the LV systolic function when we have severe MR, but in this case, because it's a minor regurgitation as the flows are higher than on the right side of the heart, we are talking between the difference between three meters per second on the MR jet and one meter per second on the MR jet, which makes the difference in pressure. 36 minus four is always going to be 32 on the DPDT. The DT is the time that it's going to take the minor regurgitant jet to reach from one to three. Okay, if it's below 1200, that means it's abnormal. If it's above 1200, that means that it's normal. You need to generate at least 1200 millimeters of mercury per second to be a competent ventricle. If you're not able to do that, it's because the ventricle is dilated. It's not able to generate this MR jet despite having severe MR. Okay, so systemic vascular resistance and the vascular resistance is just to finish that I choose with. This is based on a not very recent, this is from 2004, but I think it's probably a good way to actually get SBRs when you don't have a swan-gans if you are doing a T study. Okay, so when you need to assess systemic vascular resistance at all, we're able to actually instead of using the classical swan-gans formula of 80 per map minus mean right amount of pressure divided by the calic output, they were able to see that the relationship between the velocity on the MR jet divided by the VTI on the LVOT is stable to give you with a decent sensitivity and a specificity if the SBRs are high or not. Okay, the most important part is if this relationship is below 0.2, the sensitivity is almost 92 percent and the specificity is 88 percent to say that you don't have high SBRs. And if it's about 0.27, it's highly predictable of having high SBRs. Applying the same principle and that was described by the same author in 2013, the pulmonary vascular resistance can be calculated from instead of the regular PA catheter formula, the relationship between the velocity in the TR and the RVOT VTI. That's actually the same principle that we use for the system vascular resistance. And what it's telling you is that if this relationship is more than 0.27, exactly almost 30 percent, so if you have a more than 30 percent relationship between the velocity in the TR divided by the velocity in the RVOT, that means that is highly suspicious for high pulmonary vascular resistance. So to finish, I wanted to actually let you know what other values CVP can be estimated by the cardiologist. They normally guess how much is the CVP, but there are several formulas that have been described. This one you obviously can't remember. You need to write it down. So it'll be more complicated, but it can actually be calculated with the tricuspid valve inflow. It's pulmonary Doppler on the E wave. And this is described at MERS in 2016 in the current opinion of anesthesiology. The pulmonary capillary wedge pressure, exactly from the middle of a shear force chamber, applying this formula that you can see here, and based on the mitral valve inflow, pulmonary Doppler on the E wave and the mitral annulus T-shoe Doppler E prime, between the relationship of the two of them, you can actually get the pulmonary capillary pressure. And the pulmonary vascular resistance that we wish to stock between the relationship that was before, the formula that MERS et al. gave for that, is showing here on the right side how to get those velocities from the middle of a shear force chamber and the trans-gastric RV and the basal view. So as a conclusion, there is various thermodynamic data that might be obtained with non-invasive Doppler echocardiography. The Doppler-derivative thermodynamic data has a great impact on clinical decision making, and the delivery barriers are time consuming, but can definitely be obtained. So I hope you enjoyed the lecture. That's all for today. We will ask you some multi-choice questions on the review session, and thank you very much for listening.