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EP Fellows Curriculum: Pericardial Anatomy and RV ...
Pericardial Anatomy and RV Anatomy
Pericardial Anatomy and RV Anatomy
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taking the time, and it's a kind of a rare honor and a privilege for me to present to all of you. And this content is intentionally sort of oriented toward an EP audience, then of course, you know, anyone who's also in other areas of cardiology, hopefully, and enjoy it. So, going on to my first slide. So, this is our mission statement of our group, and I put up this slide in almost every talk that I give. This is a requirement of the presentation over here where we have to talk about our disclosures, and the disclosure is here in the bottom part of the slide. But I'd like to take this opportunity to thank all my colleagues on this slide, which, I mean, they are the very best people, and I actually miss not physically seeing them, every one of them every day. We are now having a skeletal crew because of the COVID crisis. This also recognizes all the funding agencies we've had over the years, and it's only, you know, donor and public money that led to the research. The two aspects, the bookends of the slide, and the left upper corner you see is a McAlpine image of the human heart. You're going to hear a lot about this in this lecture, and a floral image of a procedure, and at the right part of the screen, you actually see a confocal image, which is a light sheet microscopic image of cardiac nerves. It really sort of bookends the two aspects of our work, which is we do complex interventions, and we do science all the way to the basic level, and these are the men and women, the team that does the work, and I have the privilege to present some of their work. So, we love cardiac interventions, and you're going to see a huge amount of work that we are hoping to present to you, where it is, we view anatomy as macro structure function. So, every time you place a catheter in the heart, you're getting an information that is recorded through any modality, electrical, imaging, you're really, in your mind, you're putting this in the context of three-dimensional anatomy here, and of course, you know, the purpose of this series of lectures that we have created, and depending on how this goes, we'll try to give the entire sequence online for the benefit of trainees, and also be very honest about feedback. I'm old enough to have very thick skin about things that work, things that don't work, and at UCLA, we are very big fans, and as all my colleagues are around the world in EP, science and education is what links all of us, and much like a virus that knows no borders, knowledge should not have any borders, and science should not have any borders. So, here is a, you know, the overall mission statement of these lecture series, and our aim is to actually place a cardiac anatomy in its proper anatomical orientation of the human body, and of course, this will also be hopefully an inspiration for future areas where there is a knowledge gap and where we want to do science. So, there are a whole lot of concepts that are going to be presented, but it's, my hope today is to give you orientation of the human heart, a little bit of orientation of the heart on fluoroscopy, and introduce you to what we mean by the term attitudinal terms, and then of course, we'll start with the outside of the heart and later do cardiac chambers, conduction system, and advanced anatomy. So, there's nothing at UCLA that starts off or ends without a citation to John Wooden, who is a legendary coach, and you can see in my virtual background, I always have a picture of John Wooden because he's the coach who keeps us, you know, our feet firmly on the ground. For some of the people, you know, when I grew up in India, we would say it's like the Upanishads, which is a philosophical work, but at UCLA, I would say that this man's teaching is right up there with the absolute best in what we aspire for. So, one of John Wooden's famous statements was failing to prepare is preparing to fail, and he also said failure is not fatal, but failure to change maybe, and the reason why I put this at the beginning of an anatomy lecture is because anatomy is not going to change. So, anytime you devote to it and get really good at it, it's a great investment in your career and for our patients because every single patient that is being treated by any one of you belongs to all of us, and really, that's how we have to view medicine, and in fact, all of us do. So, to put it in a much more day-to-day sort of format, and I'll give you all these rules applying in future talks, but I'll give you three rules applying. One is we have to think about EP like how pilots do, which is takeoffs are optional, landings are mandatory. So, don't start a procedure if you do not know how to handle it and safely finish the procedure for the patient, and 90% of EP procedures are elective. Therefore, there is no excuse to take on the procedure without being well-prepared, and again, never let a catheter or an instrument take you somewhere where your mind did not get to five minutes earlier. That's true, and the pilots use a nice term for this. They say never get behind the plane. Be in front of the plane ahead of it, and always have a pre-procedure, pre-flight, inter-procedure checklist, and a post-procedure checklist. The most important pre-procedure checklist is to know the anatomy of what you're going to be doing today. So, all our talks start with a little tip of the hat to history, or many of you may know this. This is the famous mural that hangs in the Institute of Cardiology in Mexico City, painted by Diego Rivera, and in this mural, maybe some of the colleagues from Mexico can comment on this. So, one of the, there are many famous anatomists in that painting, and we'll talk about this, and we would always say that this, one of the famous physiologists in the history of medicine, of course, is Michael Cervetus, and we often say, and he actually had a very tough ending, as fans of history would know. So, we always say that cardiac anatomy was a dangerous business in the Middle Ages. Fortunately, it is not so now. Most of what we do in anatomy, at least as interventionists, starts off in our world by having limited access to the heart, or we image it using some imaging modality, and of course, the modality that is still used, and it's never going to go out of style in the foreseeable future, is actually a fluoroscopy, and in fact, fluoroscopy is how we actually were able to relate form to function. So, Rengen's work, again, immortalized in Rivera's mural over here, is how we look at the heart. The other aspect of the heart, the other distinct, you know, bookend, if you will, is complete access to the heart, which is what surgeons have, and one of the surgeons, you know, is McAlpine, who created this phenomenal atlas in the late 60s, early 70s. There was only one edition of that atlas, and after a multi-year search, we were able to locate the McAlpine's collection, and it's now been digitized, and now we are in the process of sharing it widely to the world, and these slides that Dr. McAlpine had were created by mounting hearts, and he did this in a, he set up an entire anatomical studio, and he would actually pressure perfuse human hearts, and he would film them from a distance, and since he pressure perfused them, they would not collapse, so in other words, you would actually see the specimens as if it were a functioning, working heart, and these are images that I got from the McAlpine family, and this, a lot of these images you see over here are images that are taken from a distance, and things that you can instantly relate to when you do an electron atomic map or a photostrophic image of the heart, so how does McAlpine, why is McAlpine, why am I spending a few minutes on this, because you will hopefully agree with this comment that was made in his arbitrary, and that is, it is an original work that may be equal, but it'll be difficult to surpass, and of course, this book is no ordinary atlas, it's a work of art, and all of us at UCLA feel that, so first off, how does the heart sit in the chest, how is it oriented, here are two images, and this one is a CT image, and one is a gross anatomic image, and this is to emphasize something which all of us know, the heart is actually a mediastinal structure, and it's tilted slightly to the left, and it's almost, if you're looking from the foot end of the patient, the heart is slightly clockwise rotated compared to mammals that walk on four feet, for instance, so that is the first important aspect of the human heart, and so all that is right is actually in the front, and all that has the term left, in general, is behind, is posterior. Now, the terms, the attitudinal terms become very important in how we describe anatomy, and it's best to describe anatomy of the heart based on how the heart sits in the chest, so that has led to a huge amount of confusion in our field, and it's worth remembering the long axis of the heart and the long axis of the body are at two different levels, and that is a very important description, and that has led to a lot of avoidable unnecessary confusion in our field, so any terminology that I use, and occasionally people please correct me if I make incorrect comments, because it's still hard to get rid of some of these wrong bad terms, but we'll always use attitudinal terms. Here are two slides which I've kept going for the past, you know, several years. This comes from my very dear friend Mark Wood, who is Dr. Ellen Bogan's colleague. He passed away many years ago because of cancer, and I keep this slide in my collection, and I show this to all the electrophysiologists in the world, just to, in a way, thank him, and he was one of the kindest and most gentle souls. So, Mark Wood, in his lecture, and in his honor, I'm showing these two slides, and that is attitudinal nomenclature. So, superior is toward the hand, inferior is toward the feet. Anterior is toward the sternum, posterior is toward the spine. We don't prefer using that term. It's better to say superior-inferior. So, the anterior-posterior is a term that is to be avoided, because it is meaningful in the context of the chest wall and the whole body, but when the term anterior and posterior used for the heart, that leads to a lot of confusion. Okay. Medial is toward midline, lateral is away from midline. All right. So, keep that in mind. And so, let's jump into what is attitudinal views of the heart. Attitudinal views of the heart are RAO and LAO, and which all of us in EP instantly know because we are, we constantly do this every day when we go into the lab. So, here's a McAlpine image, and on the right panel, I've actually given you a still shot from a epicardial ablation procedure where we injected a tiny bit of contrast into the pericardial space, and if I now overlay the line diagrams of the border-forming structures in these two views, you can instantly see that the contrast pretty much covers the heart, and it outlines all the key structures. So, if you look at RAO in this little bay over here, which is a region where you'll see the tip of the left atrial appendage. So, you'll see that this is LV, which is border-forming over here, and then the inferior surface of the heart is actually what is border-forming is the right ventricle. And then, of course, you can see a little bit of a tiny shadow over there near the IVC, and then the contrast goes around the green vessels over here, and in an epicardial case, we put a tiny bit of contrast. You'll actually see the right atrial appendage. The RAO is a very important view because this is the view, and again, what angle you should pick, it depends on how the heart sits in the chest of that patient, and what is on the left aspect of the screen is atrium. What is on the right aspect of the screen is ventricular, and in this case, it's a standard EP setup. All of you instantly know that this is a CS catheter from the IJ, a His catheter, RV. There's a high right atrial catheter, and in this case, there's also a catheter from the IVC that is entered into the CS, so that is to give you RAO orientation, and in the RAO view, if I now inject contrast using a pigtail into the aortic root, and in this case, just to keep the screen less crowded, you have a much thinner CS catheter here, the His catheter and HRA catheter, and what you see over here is the pigtail is sitting in the non-coronary cusp, which is, of course, related to the interatrial septum, right? All of you see it on TE, recognize it, and you can use this as a marker for where the membranous septum is, and we're going to be talking a lot about that in the future when we talk about the conduction system. The next view, the orthogonal view of the heart is the LAO view, which is shown over here, and in LAO, again, contrasting the pericardial space, this patient has a atrial lead ICD and all that good stuff. This view is a very important view because this helps us distinguish what is right from left, so this is in the plane of the ventricular septum and the atrial septum in general, and in this case, you can see the CS catheter from the IJ goes all the way almost, you know, not quite close, but, you know, it's already entered the great cardiac vein, and you can see there's, in this patient, the patient actually had a stent in the LAD, which you can see as a faint shadow over here, but the LAO view opens up the, literally, the two, the tricuspid and the mitral annulae look like, you know, the two eyeballs, you know, two eye sockets looking at you, so that is the clock face view of the AV valves, and another easy term to use is use this as the clock face and say where accessory pathways are, and it's better to say anything that is in the upper part of the screen as superior and anything in the lower part of the screen as inferior. What is toward the midline is, you know, is medial, and what goes toward the borders of the heart is lateral, right, so if you keep that as your terminologies, you're going to be very clear when you communicate between teams as to what you're looking at, so lose, don't use the words anterior and posterior. That is very, very misleading, and it's an anachronism and really strongly should be avoided, so this is LAO view. In this case, again, I'm injecting a tiny bit of contrast into the aorta, the exact same position. We'll talk more about this in a future lecture. Dr. Bradfield is going to talk to you about, you know, the sinuses and mapping VT and so forth, but I want, I'd be grateful if all of you can use this as a sort of a road map for you to look at where the, how the aortic root sits and how the HES model in the conduction system is the absolute center of the mammalian heart, so that's where the conduction system, you know, penetrates from the atria to the ventricle, and in many ways, you can sort of use that as a, as a sort of a pivotal point around which you can sort of look at how the heart is constructed. I'll repeat some of these concepts in future talks so that you'll have a good orientation. This view is going to be very important for you to understand pericardial axis, because in this image, we've done complex overlays. The first, the left part of this panel actually shows a Berman angiographic catheter. Some of your labs may use it, others may not, but this is a kind of a, what looks like a swan-gans catheter, but it's, this injection ports are proximal to the balloon, so that the jets come, you know, across the axis of the catheter, and the catheter is very stable in the ventricle. We like using that, and what we've recorded here is the Lebo face image of the perfusion, so you can see the RV fills, it goes into the PA, and you'll see the Lebo face, and on the right panel, you see the LAO view of the same image with an overlay of McAlpine slides, okay, so we'll spend a few seconds looking at the left. That panel, the contrast is going through, and this is the exact same patient, it was shot in my plane, okay, so this is RV, and you can see, I've just kept the his catheter in the location to keep, you know, to reduce the crowding in the heart. Now, I'm going to overlay on the left image the line diagram of what you're looking at, and over here, what you see is the structure that you're looking at during a ventriculogram, all right, and the left panel, what is shaded in red is left ventricle, and all that is shaded in with a blue outline is right ventricle, all right, so this is a huge amount of information, but I'll again revisit this one slide in future talks when you do catheter ablation of VT, please sort of, we'll revisit this, this is not your only opportunity, because the main point I want to bring to your attention here is in the RAO view, there are parts of the right ventricle that are border forming on the diaphragmatic surface of the ventricle. This area is extremely important for catheter ablation cases, and in fact, I hope you can see my laser pointer over here, the part that I'm showing you over here, this becomes very important because this area is exposed to risk when you do a pericardial axis, and in the LAO view, again, when it plays, you'll see this. In the LAO view, what is to the right side of your screen is RV, and then what is border forming in the more leftward side of the screen is actually the left ventricle, and this area also roughly tells you where the PDA is going to run so that you can find your access point to the pericardial space in general to avoid coronary arteries, which are going to be running in this view, you know, sort of foreshortened. Later, we'll come to, you know, the orientation between the membranes and muscular septae, and when we talk about the intracardiac structures, but for the purposes of this first initial kickoff talk, please keep track of the fact that what is border forming, all right? Now, having empowered with this knowledge, let's jump into axis. So, tomorrow, you're going to be hearing a dear friend of ours, Dr. Calkins, talk about ARVC, and you'll see that, you know, epicardial ablation has had a huge impact in the world of VT ablation, and how do you get into the pericardial space? So, this is all the structures in the chest wall, internal organs, and how do you access the heart? So, access of the heart requires you to understand chest wall anatomy, knowing the fact that the heart is actually covered by the pleura and the lungs, and the access to it comes from a space, which is called the Larry space. So, here we go. So, these are the structures that you have to, sort of, in the back of your mind, file away, and when you take the heart and the mediastinal structures out of the chest wall, this is how it looks. This is a preparation from McAlpine, where he has just removed the heart and the lungs from the chest, and he's displayed that, and you can see that there's only a very finite portion of the heart, the anterior part, the retrosternal part, that is visible, and the rest of it is completely covered by the lungs and the mediastinal structures. Now, if you now look at it straight on, and you cut the visceral rear of the pericardium, we're going to be revisiting this quite a bit, and where Dr. McAlpine has placed these little beads is the reflection of the parietal pericardium onto the great vessels, all right? Once you open that up, you actually can see all the structures of the heart, and this would be the equivalent of an AP view when you look at it, you know, in anatomy books and chest x-rays. So, AP view. So, AP view really is not of great value for us in electrophysiology, because it's not RA or LA. It's not attitudinal, and AP is perhaps the most, you know, inelegant view for cardiac interventions. I mean, look at this. The LAD cuts across here. This is RV. This is LV. It's like a mishmash. It's a little bit of everything type of a view. So, now, with that piece of information, let's briefly look at the cut edges of the pericardium over here near the superior mena cava, which is where my laser pointer is pointing to, and this is the aorta. This is the PA. This region, of course, we're going to be talking about this in the future again, is going to be very important for laser extractions and the dangers of what happens if you actually had an exit of the extraction tools. The location being, you know, medial-sternal versus intrapericardial bleeds. So, this is a, the reflection of the pericardium become very important. So, again, planting seeds for the future, keeping, you know, keeping that in mind. So, now, let's use a very important resource, and that is the Visible Human Project, which is a resource that's available, and this was done by the National Institutes of Health, and in this example, I'm trying to give you an orientation of how a needle can access the pericardial space. So, this is the chest wall, and what you see over here is a cut that is being in the plane of the chest and the body, and we are slicing it step by step by step. Now, you see the sternum is appearing. You can see the xiphoid process. The next cut, the sternum and the xiphoid has been removed, and you can see parts of the RV are beginning to appear, and as you get deeper, you can see that now you see the diaphragm and the complex relationship between the liver and the pericardial space, and now you can actually see that, you know, what is shaded in blue over here is the pericardial space itself. So, there's a thin layer, and it immediately becomes obvious that the pericardial space is a potential space, all right? So, a quick look at that image tells you that there are lots of dangers of pericardial access, and that is you can get RV perforation. You can get pericardial bleeding. I just showed you the liver. You can damage the liver. You can get abdominal bleeding if you hit one of the blood vessels in the diaphragm, and of course, you can enter the pleural space. Lots of dangers. So, how do you, you know, how do you avoid these dangers, and what do we have? The tool that we have is over a century old. We just have to literally take a needle and enter the space. There are new technologies that are coming up, but nothing that is yet widely used to make this procedure stress-free, but no matter what tools you have, you still have to understand anatomy. So, when we talk about anatomy here, a quick historical tip of the hat to Baron Larry, we call it the Larry space, which is the space with which, you know, the area through which we access the pericardium, and it's, of course, he's named, he's a very famous French physician and surgeon. He was in Napoleon's Grand Army, and he is, of course, a father of triage, and was a widely respected physician, and he's credited to being the first one who created ambulances. So, during a battle, he would actually take his little wagon and go pick up soldiers, and irrespective of class or distinction, he would, of course, treat the people who can be treated. So, his writings are very fascinating. So, those of you interested in history should look it up. So, how do you put Larry's space in context of anatomy? So, here's a series of data. This is in a paper that my colleague, our anatomy fellow at UCLA, Dr. Shunpei Mori, is putting together, and I'm going to be showing you data from his and other papers that we put together. This is a reconstruction for you. When you're looking at a patient, this gives you the chest wall anatomy and what lies beneath. So, the reconstruction in the front actually shows you all what I mentioned to you before, which is the lungs, and the fact that the right lung covers a little bit more of the heart, and the left lung actually has a small area because of how the lobes embryologically develop that you can see a little bit more of the heart over there, and most of the right ventricle is retrosternal, and this is the xiphoid process you see over here, the xiphoid process, and these are all the chest wall muscles over here, and in the left side, the muscles have been removed, and this is reconstruction, which took days to do. You can actually see the bony reconstruction. So, this is a, for the first time, we are demonstrating this to the world, and this information is very useful for navigating the heart, and the two things that you need to know is there's a lot that is written on the literature about the anterior versus the posterior approach to the pericardial space, and over here, I'd like to sort of bring your attention to irrespective of which area that you take for accessing the heart, whether an inferior or an anterior stick. Inferior is you sort of slip underneath and try to avoid most of the RV, and the other stick, of course, is the anterior stick, where you image the body in a lateral plane. No matter which approach you use, the first part of the heart that you actually go through is the chest wall, and this, I'm going to pause for a second because I really would like the audience and the group to appreciate this a little bit. One of the dangers of the pericardial axis, among the numerous dangers that we have, the problem starts literally underneath the skin, and why am I saying that? These are all the problem vessels that you deal with, so this is a reconstruction which, you know, Shumpei has done with a lot of effort, and what you see over here is the overlay, so these are the vessels that you are sometimes, no matter what you do, there is a finite risk of getting this, and if you are somewhat careless, and if you don't pay attention to anatomy very carefully about your point of entry, you could damage some of these vessels, especially the vessels, and there are reports, as many of you know, of internal thoracic artery injury, so the problem begins there, and if you look at the left part of the screen, then comes the whole three-dimensional dive, if you will, where you have to sort of avoid the liver to get into the space, so it doesn't matter whether you do anterior or inferior, there's a lot of problems between the tip of your needle and your destination, which is the pericardial space, and what about the pericardial space? It's a problematic space because it's a potential space, and really, this is an autopsy specimen where, you know, already the heart is shriveled up a little bit. Normally, these two layers are touching each other, so that adds to your challenge of getting there. Here are two reconstructions that we put in, and this is, again, this is a direct recognition, Shumpei Mori again, and in this presentation, what you're seeing here is the, you know, the movies, and hopefully, I'll get this to play in a second. These are two layers of the pericardium, the parietal and the visceral layers, and the purpose of this animation is to give you an appreciation of what lies beneath, and when you go from the tip of your needle, and if you can, sort of, in your mind, think of all the structures that you're going to be crossing through. That has been demonstrated in this animation, so I'll play this again for the benefit of the audience, which is right here, so that is, you know, for you to know where it is, and in this example, we've also sort of shaded where pericardial catheters are generally positioned, and this is from an actual patient who had a VT ablation. We did this full reconstruction. I'll probably pause here for a second to see if there are any questions at this point. Nishant, are there any questions at this point, because I wanted to make sure that I paused for a second to answer any quick questions at this stage. Yeah, that's probably a good spot. I haven't received anything in the chat. Oh, here's one. Okay, if you could talk about surface landmarks in terms of access, and then, I guess, just because there are a lot of fellows on, how do you advise your fellows when they're taking on these epicardial procedures when they're done? You know, do you tell them that they should be sent to a major center? Should you, do you tell them that, go ahead, you've done enough during training? How do you have them approach it? Sorry, I was muted in my mistake. So there are two very good questions. One is the immediate question, which I can answer based on this lecture. The second question is a question that involves both anatomy, judgment, your practice environment, and ultimately, what qualifies for independent flight, right? So I'll start off with a tougher question, which is the second one. Always when you start in a new place, it goes without saying, we say this to all our fellows, choose your cases carefully. If you have senior colleagues, talk to them, discuss with them. If they are not physically at the location where you practice, call your program directors, call the people who trained you, call other colleagues and briefly run the case by them because they can give you a perspective. There are certain aspects of how to do a procedure, which I did not have the time to do today because I wanted to make sure that I communicated key anatomical concepts. Always make sure that the patient doesn't have coagulation issues, liver enlargement. Make sure they don't have the interposition of the colon between, look at the chest x-ray. So there is a little bit of a pre-flight checklist of how to. And Nishant, since you're the director of this course, if you do such a session, we'll bring up some of those questions and what is not in the literature, be careful to make sure that that doesn't affect us. Last week, I think this was in JCE or somewhere, there is a very nice paper that shows some people actually have very long xiphoid processes. Therefore, you may actually have a longer path to go into the chest wall. So I think it's about case selection. So the second question which was asked is, it's case selection and being careful and looking at all the, even the uncommon things that should be in your checklist as you get the history and examine the patient. The first question was, what are the landmarks? Perhaps the most important landmark is the xiphoid process and try to avoid going very close to the possible margins. And when you access it, try to stay a little bit behind the sternum and then learn to dive in. And that component of landmarks and how you feel and do this is what I'm sure your program directors and others are literally holding your hands and teaching you. So moving on to the next part of this slide, you've seen this 3D recon. So let me take you to a kind of a real world case. This is a paper that was published by Jason Bradfield several years ago. And in this case, we actually put a alligator clip onto the needle and we are actually showing you the track of epicardial axis. This is a CT reconstructed, the heart sitting over the diaphragm, as you can see. And now when you overlay, we did an electron atomic map of the RV endocardium seen over here. By the way, this was the pre Twitter world. So this would have been a very beautiful tweetable image. But what you see over here is the needle. The needle is now visible in the electron atomic mapping system. In real world practice, you may not have the liberty and the luxury to do this. But if you plan your procedure well, you could actually see this. And the purpose of this is this is an overlay of the electron atomic map onto the CT. Now, during a case, you can actually literally see this. And the purpose of this procedure is that when you get the needle closer and closer to the pericardial space, especially there's adhesions and so forth, you can always use this as a guide to say, oh, my God, I don't want the tip of this needle to ever get near this electron atomic voltage map. Does that make sense? So if you've gone there, it means you've gone too far. So that is kind of how that is done. And this is really showing you the 3D dive angle of how you go over the liver and get into the pericardial space. Now, having with this piece of information, I'm going to show you a video of if you're visibly looking at a needle as it's sticking the pericardium, this is how it's going to look. So I let this video play, and I'll play it a second time. What you see over here is a near-field view of a needle perforating the pericardium and entering the pericardial space, all right? And you'll actually see this. This is the wire. So I'll pause this for a minute and play this again for the benefit of the group. And just before it plays, let me explain to you what you're going to be seeing. On the left lower corner of the screen, you're going to see the tip of the 2E needle, the curved little tip. It's going to be coming in to the left lower corner of the screen. The beating surface of the heart that you're seeing this, which actually has tiny little pericardial arteries and veins, you'll actually see that. The needle is going to actually puncture the pericardium, and then a J-tip wire is being threaded in the pericardium. And once the wire is in, it'll look as if it's like a little worm. It's wriggling into the pericardial space. And at that time, the 2E needle is being withdrawn back, and you'll just see the wire sticking out of the pericardium, okay? All right. I'll roll it here for you. Needle is coming in. Do you see that? That's the needle. We just took the pericardium, wire going into the pericardial space, needle coming back, and that's the wire sticking out of the pericardium. And once more, for the benefit of the whole group. And that's the wire. All right. So now, let's make a few comments about mapping and ablation so that I'll stay on time. So once you're in the pericardial space, there are some important concepts for you to know. There is almost virtually no region of the heart that is on the outside of the heart that cannot be accessed using epicardial mapping. And there are anterior axes. Once you're in the space, you can go in front of the great vessels, map all of the tricuspid annulus, all of the RB, relevant for tomorrow's lecture. And then, of course, if you go through the oblique sinus. So there are two sinuses in the back of the heart. One is called the oblique sinus. Another is called the transverse sinus. And people get very confused about these structures. And I'm going to use this opportunity to give you and introduce you to how to look at 3D anatomy of the heart. So if you look at the heart and remove the chest wall and cut the parietal layer of the pericardium, these are the vessels you see, aorta, right atrial appendage. You already saw that at the PA. And if you cut the heart out, and if you look at the cut edges of the pericardium, this is how it looks. This is the inferior cable vein, the superior cable vein, aorta, PA. And these are the four pulmonary veins. And this is the cut edge of the pericardium. Do you see that? These are actually the cut edges of the pericardium. So the part of the pericardium that goes behind the great vessels over here is called the transverse sinus. And the part of the heart that is behind the LV and the LA is called the oblique sinus. So this is a very confusing term. How do you make sense of this? And this is a very important reconstruction it took days to make. The way you should look at the pericardial space is shown in the left panel over here. And this is a paper that's being submitted. You'll actually see that it's almost like a fist going through a balloon, which is shown in the upper panel. This is the embryologic heart that is developing, which has a arterial pole and a venous pole. And when the heart develops, as you know, it's a tube. And then it folds on itself. And when it folds on itself, it has a venous pole, which actually has the cable veins and the pulmonary veins. And then it has an arterial pole, which is the pulmonary artery and the aorta. So when these structures fold on themselves, that's how the sinuses form. So the transverse sinus is shown here. You can see this. And essentially, what the heart, the way the pericardium does is the pericardium actually has two little holes, orifices almost. So the arterial pole is here. And this is the venous pole. So this literally is the hilum of the heart. And all the mediastinal nerves and the structures that enter the heart actually have to use this arrangement. Because within the pericardial space, there are no nerves, there's no structure that connects the parietal from the visceral layer of the pericardium. It's actually smooth. That's why fluid can float around it. So if you see any kind of connections there, it means it's an adhesion. So that's an important concept to keep in mind. And we don't have time to go over this in great detail, but you'll be reading this in the paper. This is very important. So the heart, the pericardial space is almost like a glove that encases the heart. And it has the two fingers for the glove. The fingers are where the vessels go into the heart, which is the veins and the arteries that bring blood out of the heart. So that's an important concept to keep in mind. And that is what, when you see in dissections, you can actually see. And this is another beautiful McAlpine dissection, where if you open the heart and if you take the heart out of the chest and look at the reflections, you can see the oblique sinus and the transverse sinus of the pericardium. So that is, again, in the right lower corner, what you see is the cut edges of the pericardium. Now, one of the ways we visualize this, of course, in the EP lab, the oblique sinus, which is the part behind the heart, here there's a pericardial ablation. We put a pigtail catheter in this case. It goes all the way behind the heart. It's in the oblique sinus at the very top. This catheter is in the RVOT. You can see that. And this catheter goes from the IVC to the SVC. So it gives you the orientation. Now, this oblique sinus is this part, like if you do a standard parasternal 2D echo, the region of the heart that you see behind the left atrium, you see where the arrow is pointing to the echo image. That is oblique sinus. So if you're assisting a cardiac surgeon in the OR, it's the part of the heart where you put your hand underneath the heart. So that is the orientation for you to tell you where the sinus is located. Another way to look at sinuses is something that very recently was published by Dr. Morey. And Schumpet did a very interesting reconstruction of a patient who had a pericardial effusion. And then he asked a simple question. OK, why don't we get rid of the heart and look at the 3D structure that is left behind? That essentially becomes a casing of the pericardial space. And that, for the first time, you can see that, in this case, the pericardial fluid has gone into the recesses. Now, several years ago, we thought, aha. So if we can use this, why don't we actually try to visualize this by taking a patient. This is a patient who had a VT ablation. And after the VT ablation, we took the patient to the CT scanner. And the patient needed a CT scan. And at that time, we put contrast with the pericardial space. And we obtained an image. And we have done a 3D reconstruction of the pericardial space alone. So this is kind of the first of its kind image. And what you see over here is the arterial pole, which is where the PA and the aorta come out. And here are the pulmonary veins. And this little area that you see over here is the transverse sinus. Do you see that? That is a contrast that is going through that area. So this is oblique sinus, transverse sinus seen in a patient, this patient had a VT ablation, did well. And you can actually see the shock lead, which is in the RA and the RB. And it serves as a good orientation for you to tell you where. So that is an image of all you see is the ICD lead. And you don't see any heart tissue at all. You're only looking at the pericardial space. So I'll read this rule for a minute so that you can see the arterial and venous poles of the heart. This is the PA. This is the superior and inferior cable vein. And you can see this is pulmonary veins, the aorta. And when you take away these structures, what is left behind is the 3D pericardial space. So that is the living anatomy of the pericardial sinuses for you. Now, I'll also show this to you as a 3D recon so that you can fully appreciate how the two layers of the pericardium interact. And this animation is to show you that finding. And we are getting close to the end of the hour. So it's the exact same heart so that all our colleagues who are on the phone will have the orientation. And this, by the way, is the pericardial drain you see over here, catheter. So the double layer reconstruction, what I showed you was the two layers. The visceral layer is the layer right over the heart. The parietal layer is the layer that covers. And if you go one step below, remove the cardiac, the heart out of this image, what I just showed you, you can actually see the transverse sinus that is running behind the great vessels. And again, imagine and in your mind, look at the pericardial space as a three dimensional space. And that will immediately tell you how to navigate yourself around in the pericardial space. And so this is a, we don't have time to do this. We'll save this for the next talk where we look on case selection and how you do anterior versus inferior axis. And I'll just make a quick closing comment on all the pericardiac structures, which are important for epicardial mapping. And that is the phrenic nerve and the esophagus, all of which you can protect and the lungs too, which you can protect carefully by shielding catheters. And one of the structures that requires a lot of care, of course, are the coronary arteries. And of course, if you inject contrast, we always, each lab is very different. Our group is very compulsive. We always do coronary arteriography before applying energy in the pericardial space, because that's very important because you don't want to damage coronaries. And there are very important insights that you get from epicardial mapping, whether it's a pathway or VT, the information that you get from that surface actually helps you guide ablation. There are specific locations, such as the pyramidal space near the base of the heart, where there are important nuances to epicardial mapping. And that is the extent of pericardial fat and the presence of veins and arteries. And more on this during future VT ablation courses. And also how there are times when you have to do multiple accesses, especially when you have complex post-receptal pathway. And again, post-receptal, you should catch me and say, aha, you caught me with a bad term. So this would be pathways that are close to the crux of the heart. So these are areas where you'll be hearing more in future anatomy sessions. Phrenic nerve is a big problem in during catheter ablation. Here's an example of a VT that is very close to the phrenic. You can see diaphragmatic capture. And how do you prevent this? You can place a balloon in the pericardial space, inflate it so that you physically separate the catheter from the phrenic nerve and you can safely ablate. And this was many years ago, my colleague Eric Bush published this. And this is now standard practice in many labs around the world. Several groups, Dr. Stevenson's group, Dr. Marchalinski's group, and Dr. Natale's group have all published on this. Sometimes they inject, in addition to placing a balloon, they also inject fluid and air into the pericardium to sort of separate the phrenic nerve away. So that's phrenic protection. And I'll leave you with one thought. A future paper that's coming out on this subject, we are gonna actually upload stereolithographic files for all our colleagues around the world. So anyone who has access to a 3D printer can actually print the model of this heart and literally put these structures together. And you can actually use that for your own learning because you actually have to hold that in your hand to see how these spaces work. So I'll stop here right on time. Thank all of, you know, anatomy team at UCLA, which is Dr. Hanna, Hayase, Ching-Shu, Mike Deasy, Joe Dyer, and Shumpei Mori, and our digital expert, Michael Papaloukas. And look out for 3D models you can print and use. And I will stop here. Thank all my colleagues at UCLA and turn it over to Nishant for any questions and comments. And thank you so much for this opportunity. You know, it's at a time when it's very stressful for the whole world in this pandemic. It's nice to, you know, take a few moments to sit and think about all of what we do. Thank you all so much for your kindness and your patience. Nishant, I'll hand it over to you. All right, thanks Shiv. So that's amazing and some incredible images that you showed us. There were some questions, and as Shiv alluded to, we probably will have future talks on epicardial VT ablation. So there were questions on, you know, the process of getting epicardial access. Do you ever use ultrasound? You know, what fluorobuse do you use? Do you want to just briefly go through that? We may have future talks on that as well. And I put a link to your article in the chat for them to look at as well. Yeah, thank you so much. I think what we should do is, fluoroscopy is 99.9% of all of epicardial access is done under fluoro. This is not yet at a point where you can do it without fluoroscopy. And what we ought to do is, perhaps in a future round table that Nishant, you've been alluding to, when you do that, we'll completely sort of go through a recorded case in a box. And not to say all what went great, I'll actually, we'd love to actually come up with a discussion where we tell you all the things that can go wrong. Josh Moss, who's a good colleague of ours, friend at UCSF, is putting together a sort of a teaching session, which we want to practice this before we present this to the world in front of all our friends, as a way in which how to have, you know, what are points of no return and when to abort a procedure. So for some of the people in this call, go look up the term RTO, rejected takeoff. That is a term that pilots use all the time. And in the world of EP at UCLA, we always use that, which is to know when to abort a procedure or when to abort and stop an approach and say quit while you're ahead. We'll definitely present that. But the simplest answer that I can give you is it is highly fluoroscopy dependent as it stands, at least for epicardial axis. Every other approach that you use is ancillary. It's a piece of information that helps you factor in how you do it. And one other point, if patients have had previous cardiac surgery, be very careful about epicardial axis. We have done it, some other centers have done it. And to answer the first question, which one of our younger colleagues asked, don't do that as your first case when you're in practice, wherever you go, because that's when there are a lot of adhesions and there is a significant risk of injuring vessels because the heart may be adherent to the wall there. And then the only other comment was from Uma who wanted to say that AP view is okay if you're trying to minimize fluoroscopy and rely on your map. Yeah, that's actually fundamentally true, but that comes from a highly experienced operator. And an even better way maybe to minimize is to use RAO. So you can just quickly check on LAO for your angle of attack. And then instead of even AP, use RAO because you'll reduce your radiation exposure even more. But interestingly for epicardial axis, for the actual moment where we puncture with the needle, we actually use a much more higher resolution fluoroscopy almost in cine mode, where the energy use of the x-ray system is much higher. So we actually have programmed our fluoroscopy systems to actually, we take that short duration of a few seconds of intense fluoroscopy just so that there is very clear definition of structures. But the trade-off is RAO maybe a little more tissue the x-ray goes through, but then you can compensate for that by increasing the KEB on your system. So you can program your fluorosystem to do that. But again, judicious use of all available information because much like what a transseptal is to an AFib, if you're doing an epicardial procedure, if any part of this procedure is messed up or suboptimal, that could come to haunt you for the entire case. I'd also like to make another comment with your permission, Nishant, to the whole group. Please, if you email Dr. Varma, if he can collate any questions that come up, we'll go through them and we'll make every attempt to answer this because there's not a single question or comments that come from any of you that is not important or irrelevant because I often wonder, this is a moment where this format actually allows us to answer some of these questions asynchronously. And certainly when we do the second part of this in the future, because anatomy is never gonna change. And I'm also trying to put together a global consortium, Sam Asarvatham, Rod Tong, many of our, Fermin Garcia, there is a little anatomy fan club in the world. So we will definitely collate all these questions and bring this up in future content. And all of you are gonna bring up very important comments because we are here to learn. So the one thing that many professors don't often say is, this is the greatest learning opportunity for us and this is not meant to be pedagogical, just to sit here and show slides to people. So please, we sincerely appreciate the time you're taking and thank you for this great privilege, Nishant. On behalf of all my colleagues, we wish all of you the very best.
Video Summary
In this video, Dr. Shiv Kumar discusses the anatomy of the heart and the pericardial space in the context of electrophysiology (EP) procedures. He begins by presenting the mission statement of his group and acknowledging his colleagues. He emphasizes the importance of understanding cardiac anatomy in EP procedures, particularly in relation to three-dimensional orientation in the heart. Dr. Kumar explains the attitudinal terms used to describe the orientation of different cardiac structures. He also discusses the oblique and transverse sinuses of the pericardial space and their relevance in EP procedures. Dr. Kumar highlights the importance of careful case selection and preparation in epicardial procedures, including considerations for landmarks, fluoroscopy, and potential risks and complications. He concludes by emphasizing the importance of continuous learning in EP and the intention to share more in future lectures.
Keywords
Dr. Shiv Kumar
anatomy of the heart
pericardial space
electrophysiology procedures
cardiac anatomy
three-dimensional orientation
attitudinal terms
oblique sinuses
transverse sinuses
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