 Thank you, Dr. Chan and the ISRA organizing committee for this invitation to present. My name is Azat Mashaari. I'm a cardiac anesthesiologist at Toronto General, and I'll be talking to you today about cardiac anatomy for a thoracic-erasic echo. Unless otherwise indicated on the slides, all the content here is under a Creative Commons license, and you're welcome to reuse it under the following terms. These are my disclosures. Nothing specifically to this presentation. My work is mostly funded by the UHN Foundation and my Clinical Practice Association, and I have some research collaborations with a few companies that involve only in kind support. In this presentation, I'm going to take a bit of a different approach to cardiac anatomy than you might be used to. I'm going to focus on the heart base, which roughly corresponds to the fibrous skeleton of the heart, and includes the framework that supports all of the valves and the valve annuli. It's pretty easy to memorize the structure of the heart base with a pretty simple schematic drawing, and once you do that, you're one able to quickly visualize the locations and orientations of all the leaflet cusps on all the valves, and you can use it as an anchor for all the other cardiac structures, because everything in DN has to attach to the heart base in one form or another. So we'll first go through a three-step process for drawing a schematic of the heart base. Then we'll look at the morphology of it in 3D, and its position in the chest, and its relationships to standard TE windows. We'll assemble all the cardiac structures around it, and we'll visualize the standard cut planes for echo. So on the left, it's a detailed schematic that we'll end up with at the end of our drawing process, and on the right is a 3D CT-based model of the same heart base. Look at it in the chest. So we're looking at it here from the right shoulder towards the apex, or from the direction of the great arteries in the atria towards the myocardium. I strongly suggest you grab a pen and paper and follow along. The first step is to draw three circles and mark their centers. So one circle in the middle being the aortic valve, one in front of it, anteriorly being the pulmonic valve, a bigger one to the right, the tricuspid valve, and a jelly bean for the mitral valve. And we mark all the centers. I put this orientation marker here. These left, right and anterior are in quotations because they correspond to the orientation terms commonly used in cardiac anatomy, which are not, in fact, in keeping with standard anatomic terms. The next step is to connect the centers of the circles together, and then divide each of the valves into even thirds. And with a mitral valve, we'll just put a simple happy-faced commissure. Another way to remember this is to add a clown nose to the aortic valve. So again, here are the three steps. So first we draw the three circles in the jelly bean. We mark the centers of the circles. We connect those centers, and then we divide into thirds. And we can then quickly label all of the cusps. So the aortic valve in the middle has a right coronary cusp, a left coronary cusp, and a non-coronary cusp. The pulmonic valve in the front has an anterior right and left cusps. The tricuspid valve has an anterior, posterior, and septal leaflets, and the mitral valve has an anterior and posterior leaflets. Now try to picture where the intra-atrial septum is going to be, where the right and left atrial appendages would be, and where the coronary sinus would be in the schematic. Here we've added those in, so you can see the atrial appendages on the right and the left. You can see the intra-atrial septum between the tricuspid and the mitral valves, separating the two atria and the coronary sinus wrapping behind the mitral annulus and going into the right atrium at the tricuspid valve. So next we add the silhouettes of the right ventricle and the left ventricle. Again, this is the view looking from where the atrium and the great arteries are towards where the ventricles are. And you can see that the inflow and outflow of the left ventricle are quite intimately associated, and the left ventricle has a rounder ellipsoid cross-section from this view, along with its long axis, looking down its long axis, and the right ventricle has sort of a boomerang or banana shape. And now we just add a bit more detail to the schematic. We label the separate segments of the mitral leaflets, interested in a level of detail. The tricuspid valve, in fact, is not very circular. The anterior and septal leaflets are much larger than the posterior leaflet, but you can see that the orientations are pretty well represented. The dotted lines there represent the cut planes for four-chamber views and for the long-axis views, and we'll talk about those in a bit more detail. So on the left you can see the 3D structure of the heart base. This model is available as an interactive 3D model at the link that's there. So now we're going to leave the flat sheet and move into 3D. All the models you're going to see are created from a cardiac gated CT, using an open-source software called 3D Slicer that you can download and play with yourself. What we're showing here are blood volumes of the chambers, so the walls of the vessels and all the myocardium has been removed, so that you can more clearly see all the connections inside the heart. The small man on the right will show you the orientation of any of the images. This heart has generally normal anatomy, but this patient did have previous heart surgery for aortic coronary bypass grafting or cabbage, and if you look closely you can actually see some of the saphenous vein grafts coming off the ascending aorta and part of the mobilized lima that was grafted to his LAD. He also has sternal wires that all make visible in some of the views that will help us locate where the sternum is more easily. The first key thing to notice about the 3D morphology of the heart base as opposed to the flat diagram that we drew is that the pulmonic valve and the aortic valve are not coplanar. The long axis of the aortic valve goes roughly from your right humeral head towards the apex or point of maximal impulse, whereas the long axis of the pulmonic valve is pretty well in the mid-sagittal plane, so it goes from your zippy sternum all the way back towards your C5, C6 vertebrae, and here we have that anterior and left lateral view, and you can see the sternal wires there that we've left for orientation. So once we've rotated the heart base into the right configuration, so the long axis of the LV goes from the right humeral head to the apex, the next is to actually locate this properly in the chest. The aortic valve itself is almost directly behind the sternum, and the planes of the mitral and tracheocytic valves are essentially vertical, so knowing those key features will allow you to orient the heart base in the chest. So you should be able to look at a patient and visualize the heart base inside their chest, and should be able to visualize your own heart base. Now we start adding all the other cardiac structures, so here we've added the left heart blood pool, so try to identify the left atrium and the pulmonary veins, see if you can identify the left atrial appendage, the left ventricle, and the cavity in the blood pool that corresponds to where the antrolateral papillary muscle would be. And one question is, which pulmonary vein is closest to the aortic valve axis? So you can see the left atrial appendage coming and going out of the view there, and you can see that the right upper pulmonary vein is the one that comes closest to the aortic valve axis. Now we add the aorta, you can see the ascending aorta, the aortic arch and its branches, the brachiosophallic, the left common quadrat and the left subclavian. You can see the descending aorta, and if you look closely at where the aorta takes off from the heart base, you can see the start of the RCA and the left main coronary artery as the model rotates around. So here you can see the RCA as well as the vein grafts in the ascending aorta, and here you can see the left main just a little nub there. Next we look at the right heart, you can see how the right heart is anchored at the tricuspid valve and the pulmonic valve with the right ventricle, with this fairly triangular shape connecting the two and going all the way down to the apex. You can see the coronary sinus wrapping around the mitral annulus and going into the right atrium, as well as the SVC and the IVC coming into the right atrium, and coming out of the pulmonary valve you can see the main PA, the left PA passing through there and the right PA now coming into view behind the SVC. So here we put everything together, it's a little bit overwhelming at first but again if you remember the previous figures where we did this piece by piece, you can see the right heart blood pool, the aorta pulmonary artery, the left heart blood pool, all of them anchored to the heart base in the center. So next we're going to look at the cut planes, windows and views, and that's an important distinction. So the cut planes are tomographic planes that can be sort of visualized based on three point landmarks. So for example for the LV long axis cut plane, it includes the aortic valve center, the mitral valve center, and the apex. And there are multiple windows from which we can view parts of that cut plane. So in transorastic echo we can use the parasternal window or the apical window and in TE we can use the mitral software geo window. And from each of these windows we then have specific views that include part of that cut plane. So we have the parasternal long axis for example, the parasternal AV long axis or the apical long axis or the mitral software geo long axis. TT windows are defined by the ribs and the lungs, which leave a few openings through which you can fairly reliably see the heart in most patients. So one set of openings are adjacent to the sternum just on the left, near the third and fourth to fifth interspaces, and you get your personal windows there. You have a window near the apex and it's up close to the window where you can look through the liver and see the heart. As we take the ribs away you can see how those windows correspond to the cardiac structures underneath. So the personal window overlies the right ventricular outflow tract. The subcostal window looks from beneath the RV and the apical window looks at the apex. You can see that the personal window also looks directly down at the aortic valve, whereas the apical window looks up towards the aortic valve along its long axis. Looking at the four chamber cut plane now, the three landmarks would be the center of the mitral valve, the center of the tricuspid valve and the apex. And we can look at this cut plane from the apical window or the subcostal window. So here's the same cut plane visualized on a CT with all the structures showing and on the left an on fast view of the cut plane oriented to correspond to the apical four chamber view. So you can see the apical four chamber view on the right and the corresponding CT on the heart base embedded in it on the left. Take a note of the orientation figure there. So we're looking from below in the standard TTE view. The next major cut plane is the long axis plane that we spoke about briefly before. So the landmarks again are the center of the AV, the center of the MV and the apex. And we can look at this from the parasternal window or the apical window. And here it is again with all the structures showing and on the left an on fast view. This time looking from the left shoulder towards the heart base and oriented to match the parasternal long axis view. So on the top you can see the CT cut plane and the four cardinal orientations. On the lower right you can see the standard echo parasternal long axis view and the corresponding CT window. So you'll see that the pulmonic valve would be in front of the screen and you're cutting through the RVOT closest to the probe. The third major cut plane is the mid papillary short axis cut plane which is defined as being perpendicular to the long axis of the LV. So if you imagine a straight line running from the middle of the mitral valve to the apex that would be the long axis of the LV. And this is the plane that is perpendicular to that axis and is located in the middle of the ventricle so at the mid papillary level. And we can look at this cut plane from the parasternal window or the subcostal window. This view is significant because at the mid papillary level all three major coronary circulations are represented and you also have the least chance of having geometric distortions based on movements of the heart in and out of your scan plane. So here we have the cut plane now with all the structures showing and on the left oriented to correspond to the standard TTE views. So here on the right is the standard parasternal short axis view and on the left the corresponding CT tomographic view. So we reviewed the anatomy of the heart base. We talked about how to orient the heart base in the chest, how to anchor all the cardiac structures to the heart base and how to visualize the three most significant cut planes in the chest in relationship to the heart base and all those structures. Thank you very much for your attention. I'd like to thank my lab graduates and my mentors in this work. Full references and link to the presentation and all the media content are available at the link below. Thank you very much.