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Marc Simon, MD - phaware® interview 522
05/27/2025
Marc Simon, MD - phaware® interview 522
Decoding Pulmonary Hypertension: Echo and Cath Insights for Pulmonologists. Dr. Marc Simon shares his expertise on diagnosing pulmonary hypertension, emphasizing echocardiographic markers, right heart catheterization pitfalls, and risk stratification with the H2FPEF score. His insights help clinicians refine their diagnostic approach for better patient outcomes. This Special Edition episode is sponsored by . View PDF Slides . I’m Marc Simon. I am a cardiologist and a heart failure specialist at UCSF in San Francisco. I direct the pulmonary hypertension program there. I moved there about four years ago now in 2021 for this opportunity from the University of Pittsburgh where I was on faculty for about 15 years, taking care of pulmonary hypertension patients within our cardiology section. Very similar to UCSF, in a very multidisciplinary group with both pulmonologists and cardiologists. It’s really been a really wonderful experience over these past 20 or so years. I’ve done a lot of research over the years in terms of right ventricular function and adaptation in pulmonary hypertension, really ranging from imaging with echocardiography as we’ll talk about today, MRI, some CT scans, as well as integrating with hemodynamics to understand cardiovascular physiology of the right ventricle, as well as some translational work to try to understand the biomechanics of the right ventricle, which is an exciting and ongoing story. Finally, some drug development over the last eight years or so. That’s been really exciting. As you know, with pulmonary hypertension, we’re very fortunate to have so many drugs available to treat patients, so it’s been a wonderful career so far. It’s a really interesting time in pulmonary hypertension. There’s continued to be a lot of drug development going on with a lot of focus now on ILD and related pulmonary hypertension, which is particularly exciting in a space where prior we had no therapies. In that context, I’ll be talking to you today about echocardiography and right heart catheterization for the pulmonologist. This is a talk I gave recently at the California Thoracic Society. I really look forward to presenting some of this information today as a cardiologist, I guess, talking to the pulmonary community and folks involved with pulmonary hypertension, and potentially patients as well, getting some insights as to some of the testing that we do to better understand disease and diagnose. When I think about echocardiography for pulmonary hypertension, I’m kind of thinking really sort of broadly speaking in three different contexts that I find to be really helpful to think about this. One is echocardiography, of course, useful for estimating a pulmonary artery pressure. That’s what most people will think about and that can be really useful. That echocardiography is a great screening test for the pulmonary pressure. Then, I really like to come at the echocardiogram in terms of trying to end up at a phenotype that is either right-sided or left-sided. I think that’s a really nice context to think about the echocardiogram as you’re going into this. By right-sided, I mean, sort of a RV failure type phenotype, and that’s really what we’re talking about for pulmonary hypertension, pre-capillary pulmonary hypertension. As opposed to left-sided, thinking about really ending up being group two pulmonary hypertension and all the causes thereof related to heart disease and things like this. You’ll hear me talking about right versus left-sided phenotyping as we go through some of these highlights of echocardiography for pulmonary hypertension. Finally, it’s always important not to forget with the echocardiogram, that’s a great screening test for congenital heart disease. So, of course, that’s a very unique and specific cause of pulmonary hypertension. A lot of times, you’ll get your first inkling that this may be what’s going on, on the echocardiogram. I like to start off by highlighting a study that came out a few years ago, actually, out of Australia by a Strange and colleagues, it was published in Heart in 2012. They just looked at all echocardiograms that had an estimated pulmonary artery pressure greater than 40 millimeters of mercury. All of those coming through the echo lab, out of those, two-thirds ended up being left heart disease. So, the vast majority of what we’re seeing that’s referred to us as an echocardiogram that might be suggestive of pulmonary hypertension with an elevated estimated pulmonary artery systolic pressure really ends up being left heart disease. So, again, really important to keep this in mind. Only 2.7% of those patients ended up having pulmonary arterial hypertension. About 2% had chronic thromboembolic pulmonary hypertension and 9% had lung related disease. The 2022 European Guidelines think about echo screening in terms of three contexts. This is the ventricles, the pulmonary artery and the inferior vena cava and the right atrium. Showing signs from at least two of these can alter your level of a probability of pulmonary hypertension. When we’re talking about the ventricles, there’s a couple of points. One is the right ventricle larger than the left ventricle. This can be as simple as a basal diameter in which the right side is greater than the left side. Along with this can be flattening of the interventricular septum. Those two points right ventricular enlargement, RV size greater than LV size and flattening of the septum falls into that context of a right-sided phenotype that I was mentioning. Then, talking about the TAPSE, tricuspid annular plane systolic excursion or that ratio of that to the systolic pulmonary artery pressure being less than 0.55 millimeters per of millimeter of mercury. I’ll talk a little bit about what that particular measure is. Some people like it, some people don’t. TAPSE is a measure of right ventricular function. Of course, systolic pulmonary artery pressure is the pressure afterload that the right ventricle sees. In terms of the pulmonary artery, a dilated pulmonary artery, like I’m sure a lot of pulmonologists are really keyed into. In fact, I usually receive several referrals a month based on an enlarged pulmonary artery seen on a CT scan and is this related to pulmonary hypertension. So, the enlarged pulmonary artery can also be seen on echocardiography. That can be a real phenotype that keys you into precapillary pulmonary hypertension. Also, is the pulmonary artery acceleration time. This turns out to be my favorite, favorite term in echocardiography. I’m going to talk to you a bit more about that. But essentially, it’s the flow out of the right ventricle through the pulmonary valve into the pulmonary artery, and you can measure the onset of that flow to the peak velocity. If it’s less than 105 milliseconds, call it 100 milliseconds, it’s easier to remember. That is a good cut point to say, “Hey, maybe this patient has significant pulmonary hypertension.” Again, I’m going to talk about that a lot more. Then, a dilated inferior vena cava, significant for right ventricular volume overload. Right ventricular failure, a high central venous pressure, for example, and a dilated right atrium. These are other signs of that right-sided phenotype again. Again, if you have signs from at least two out of these three categories, it can be highly significant for pulmonary hypertension. A lot of people are familiar with this concept of the large dilated right ventricle and right atrium, the flat septum, the pericardial effusion that a lot of times can be seen in pulmonary arterial hypertension. We’ll have a to some images of this if that’s helpful for folks. Let’s talk a little bit more about my favorite echocardiographic measure, the pulmonary artery acceleration time or PA acceleration time or sometimes called PAAT. If you’re in the parasternal short axis view at the valvular plane, for those of you who have looked at echocardiograms, that view where you see the cross section of the aortic valve right in the center there and on the left side of the screen is the tricuspid valve with the right ventricular outflow tract arching over the center of the top of the screen over the aortic valve, and then the pulmonic valve on the right side of the screen leading out to the main pulmonary artery. That classic view of the basal cut of the parasternal short axis view. When we look at the flow on that right side of the screen, so from the right ventricular outflow tract out through the pulmonary valve into the main pulmonary artery, we can look at the Doppler velocity of the blood flow in that direction. That flow is what we call the ejection from the right ventricle out into the pulmonary artery. Again, we can measure the onset of that flow to peak velocity because in Doppler terms, we’re measuring velocity. So, the peak of that velocity, and this is really sort of a U-shaped type of velocity envelope as we call it. So, the onset to the peak of that U, the X axis is time, and we’re measuring that in milliseconds, so, that time is the pulmonary artery acceleration time. As it turns out, it’s highly sensitive to pulmonary pressure and it gets shorter as pulmonary pressure is elevated. So, it’s inversely related to pulmonary pressure. I quiz the trainees a lot on this. Why would that be? Why is it an inverse relationship? Well, it turns out this is related to cardiovascular physiology. So, if you think back to medical school, the idea of isovolumic contraction of the ventricle, because after the ventricles filled, you have to develop enough pressure to overcome the pressure that you’re pumping out against, in this case the pulmonary valve and the pulmonary artery. So, ventricular pressure during the initial contraction phase has to develop enough pressure to exceed pulmonary artery pressure. Then, the pulmonic valve opens once that pressure gradient is exceeded. Once the valve opens, then we have ejection. After ejection is complete in terms of enough volume has been ejected from the ventricle, that ventricular pressure then starts to fall. When right ventricular pressure falls below pulmonary artery pressure, the pulmonary valve will close again, and then you’ll have isovolumic relaxation until pressure falls below the right atrial pressure. Then, filling begins through the tricuspid valve. If you think about pulmonary hypertension, the higher the pressure in the pulmonary artery, the more that the right ventricle has to overcome in order to eject its volume. If you think about the cardiac cycle being fixed, then the higher the pressure, the more time the ventricle is going to spend in isovolumic contraction to develop more pressure to then overcome the pressure in the pulmonary artery and eject. So, there’s less relative time in ejection. So, that means, all of the blood flow out of the right ventricle into the pulmonary artery has to occur in less time. You can imagine that really squashes down, that narrows down the velocity window of ejection. So, the time from onset of flow to peak flow becomes much narrower. That’s that inverse relationship between pulmonary artery acceleration time and pulmonary pressure. There was a nice paper published in 2011 actually, in the Journal of the American Society of Echocardiography, first author Yared that looked at the PA acceleration time and created an equation linking it to estimated pulmonary artery systolic pressure. I really like this because you can then relate directly the PA acceleration time in milliseconds to pressure. When I calculate that out, if you have a PA acceleration time of 150 milliseconds, that calculates out by this paper to 32 millimeters of mercury. So, not too bad. If the PA acceleration time, then decreases to 100 milliseconds, remember this is the cut point for the European Guidelines, 105 milliseconds, very close. That calculates out to an estimated PA systolic pressure of 50 millimeters of mercury. You can see right there, you’re at a significant pressure in a range where we would really say, “Oh, that might be someone we should look at further.” PA acceleration time of 50 milliseconds, which I’ve seen quite frequently, calculates out to an estimated PA systolic pressure of 79 millimeters of mercury (mm Hg). Really, that’s significant pulmonary artery pressure. Beyond just being able to have another measure of estimated pulmonary artery systolic pressure, there’s a couple other things I like about this. One is that it’s not just numeric. I’ve told you a lot about the numerics and the physiology, but that can be a little bit complicated. There’s also a qualitative version of this, which is, if you’re looking at that velocity envelope, it’s is called mid-systolic notching. Along with a steepening of the velocity going out into the pulmonary artery, on the backside of that nice U-shaped (usually) curve, you’ll get a notching. This can look like a W or an M. It’s very obvious in many cases. That qualitative sign also goes along with significantly elevated pulmonary pressure. A lot of times actually, when I’m reviewing an echo where I don’t have that measure already made for me and I don’t have the ability to measure it on my own on the fly, I’ll make a note to myself, “Oh, this patient has mid-systolic notching or this patient does not have mid-systolic notching.” Again, that to me is another one of those check boxes for is this a right-sided phenotype? There is mid-systolic notching. Or a left-sided phenotype, there is no mid-systolic notching? There’s a few examples of this that will be in the . The final reason, I really like pulmonary artery acceleration time is the incomplete tricuspid regurgitation jet. I’m sure everyone’s seen an echocardiogram report where it says there’s an incomplete TR jet. Therefore, we cannot estimate pulmonary artery systolic pressure. That occurs in really upwards of 25% of echoes. So, it’s quite substantial. When this occurs, almost always there’s a viable PA acceleration time or RV outflow Doppler signal that’s in the echocardiogram and can be pulled out. Even in these indeterminate echocardiogram reports, many times, we can actually come up with an actual estimated PA pressure using the PA acceleration time. The other things I like to look at with the echocardiogram are right ventricular function. We’ve talked a little bit about right ventricular structure, is it dilated or not? We’ve talked about the estimated PA pressure and the related lauded pulmonary artery acceleration time. Finally, let’s talk about right ventricular function. So, again, diminished right ventricular function will fall into that right ventricular phenotype echocardiogram versus normal right ventricular function, maybe, there’s not a significant pulmonary hypertension. There’s a number of metrics now out there to help evaluate right ventricular function. One of the main ones that I would say is reported on more echoes than not these days is TAPSE. Probably, a lot of people are aware of this. It’s not a new measure at this point, but it is related to the longitudinal motion of the right ventricle. This is a large portion of right ventricular function, not all of it, but a large portion of right ventricular function. We can measure how much motion is in that tricuspid plane just by measuring in one dimension the motion in centimeters or millimeters. The more motion there is, the more normal the right ventricular function is. There are various cut points between 2.0 centimeters, that’s 20 millimeters and 1.6 centimeters or 16 millimeters. Why is this so important? There are a number of papers that had come out thathave associated related diminished TAPSE with poor outcomes. There’s a lot of prognostic value with this. It’s highly correlated with pulmonary pressure. So, it’s a really useful term to have in our reports. This is one of several that I’ll try to write down. The next one is what’s called right ventricular S’. S stands for systole or systolic contraction. The prime (‘) indicates that this is a tissue Doppler measure. So, we’re actually measuring the velocity of the tissue in this case and not the blood. If we look kind of in a similar spot to where we look for TAPSE on the lateral wall at the basal level near the tricuspid valve, we can put a cursor there and we can measure the velocity of the myocardium of (the muscle of the right ventricle). A cut point for this is about 10 centimeters per second. If you’re above this, you have vigorous contraction. If you’re below this, you have right ventricular dysfunction. Again, another measure that is in many reports these days, I’ll add it along with TAPSE to sort of complete this story. I kind of find that with right ventricular function. Remember, the right ventricle is a very complex three-dimensional structure. Echocardiography is a one-dimensional or two-dimensional modality of imaging. You need to provide multiple views, multiple metrics to really best describe right ventricular function I find. I don’t think any one measure is good enough to really give you a full picture of right ventricular function. The more of these you can sort of put together the better. So, we have TAPSE. We have right ventricular S’. Then, there’s also strain, right ventricular strain. In this case, we’re looking at image processing of the right ventricle, and we can look at the shortening of the myocardium from one frame to the next as the right ventricle contracts, and the percentage shortening is correlated with right ventricular function. We can look at the free wall of the right ventricle. We can look at the septum. We can average all of those together. More often than not, I like to look at the mid right ventricular free wall, a shortening of minus 20% or so in absolute terms, more, if you want to talk about it or in negative terms, more negative is normal function, and less than that is abnormal. Then, more recently, there have been some attempts to put together several of these metrics to help us guide is this more of a right ventricular phenotype, pulmonary hypertension, precapillary pulmonary hypertension phenotype, or more of a left-sided phenotype or Group 2 pulmonary hypertension phenotype. One of these is the VEST echo screening tool, which looks at three parameters. One is the mitral E/e’. I haven’t talked about this too much, but this is a measure of left ventricular diastolic function. I put left ventricular diastolic dysfunction into that left ventricular phenotype category. You can have a whole lecture just on that alone. But another probably good point to look at and keep an eye open for on our echocardiograms is simply has there been a mention of a grading of left ventricular diastolic function? If there is, that might be one of these warning signs that maybe we’re dealing with a left-sided phenotype. But in any event, the VEST echo screening tool looks at the mitral E/e’, looks at left atrial size. We talked a little bit about right atrial size. A dilated right atrium, a significant for precapillary pulmonary hypertension, that right-sided phenotype. A dilated left atrium is a big marker of left-sided disease. Then, finally, septal flattening. We’ve talked about that before too. So, more to come on that measure (VEST echo screening tool), I think, as there’s more work being done on it. With that, I’ll switch gears to right heart catheterization and talk a little bit about that. So, with right heart catheterization, as...
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