Point of Care Cardiac Ultrasound (Echocardiography, POCUS)

Hi, I'm Dr. Andre Kumar. This is the Stanford 25 ultrasound series. In this video, we will be discussing cardiac point-of-care ultrasound. Cardiac point-of-care ultrasound has expanded across several specialties and can be very helpful in the evaluation of patients with certain cardiac conditions. Like with anything in POCUS, use it to enhance your clinical examination and judgment, but it should never be used to supersede your judgment otherwise. There are several strengths and limitations of cardiac POCUS. Some of the things that it's quite good at doing is the evaluation of chamber size, gross valvular abnormalities, systolic function, central venous pressure, and evaluation of a pericardial effusion. Things that it's a little bit less reliable at doing include valvular gradient-specific measurements, the evaluation of vegetations as seen with endocarditis, diastolic dysfunction, as well as wall motion abnormalities. There are four classic views that we use for cardiac point-of-care ultrasound. These include the parasternal long, parasternal short, apical floor chamber, and the subcostal, also known as the subxiphoid. When you're thinking about scanning, you want to use a phased array, also known as a cardiac probe. When you're scanning, the dot is located on the right side of the screen, and if you're using a device, be sure to set it to cardiac mode for optimal gain, depth, and frame rate. As we begin our examination, there's a couple of landmarks that you want to be aware of for your patient. You want them lying flat, completely in a hospital bed. If the head is up, try to lower it as best you can. You want to make note of the xiphoid process, the sternal border, as well as the midclavicular line. These will be really important when we're thinking about probe placement. Let's begin our examination with the parasternal long. Go ahead and get my gel. The parasternal long is a great view that's easy to assess. Systolic function, pericardial effusion, gross abnormalities of the mitral and aortic valve, and a little bit of chamber size. What you want to do is place the probe generally in the second to fourth intercostal space on the patient's left side, just next to the sternum. The marker of the probe should be pointed towards the patient's right shoulder. Going ahead and place my probe here. And so here we can see a very nice parasternal long view. We can see the left atrium, the mitral valve, the left ventricle, the aortic valve, and towards the top we can see the right ventricle as well. And when we're thinking about troubleshooting this view to get the most optimum view possible, there's a couple of things you can do. First of which is you want to center the aortic and the mitral valve in the image. In order to do that, you can rock the probe back and forth until you get an optimal image. So I'm going to show that now. Here is me rocking the probe. I'm exaggerating that movement a little bit, but you can see me rocking it to bring this into a more centered view. Another common thing that I see is the aortic valve may be incompletely visualized in this view, and that's entirely related to your scan angle. What you can do is right now my probe is almost perpendicular to the patient's chest. What you can do is have the probe pointed a little bit more towards the head, or I'm changing my angle so it's more towards the patient's head, and that brings the aortic valve more into view. So just to demonstrate again, can't really see the aortic valve. Now I'm pointing the probe a little bit more towards the head, and it allows me to visualize it much better. Another thing that I often see is if you are seeing just too much black, that might mean you're over a rib or the sternum. Here I can actually feel the sternum, and so what I want to do is just slide my probe over, and I'm able to visualize the parasternal long view much better. So now we've done the parasternal long, let's transition to a parasternal short. A parasternal short is a great image to look at cardiac function, particularly systolic function of the left ventricle, the right ventricle, as well as evaluation of the mitral valve. So let's talk about the parasternal short. If you're in a parasternal long, it's actually quite easy to get parasternal short. You don't need to lift up the probe. All you need to do is just rotate the probe about 60 to 90 degrees, and you'll be able to get the image. What I do is I use two hands, so I keep one of my hands firmly anchored on the patient, and I simply rotate the probe about 60 degrees, so now it's pointed toward the patient's left clavicle or left shoulder. When I do this, I'm able to see a short axis view of the heart. The probe positioning for the parasternal short is extremely important. Depending on your scan angle, you're able to see various different structures along a short axis of the heart. For instance, if I have my probe and I decide to point it more anteriorly, or in other words, more towards the patient's head, so I'm pointing it more towards the patient's head with my angle, I'm able to see the aortic valve, the tricuspid valve, the pulmonic valve, all very easily in my view. If I want to see more inferior structures or more towards the apex of the heart, I have to imagine I'm pointing my probe more towards the apex, so rather than having my scan angle towards the head a little bit, I'm going to change it, so from going from this angle more towards perpendicular. When I do that, I can see what's called a fish mouth view of the heart. Here I can see the left ventricular cavity and the mitral valve opening and closing, and if I want to go even farther and see the apex of the heart, I take my angle and I point it more towards the apex of the heart. By doing this, I'm able to visualize the papillary muscles, which is extremely important for systolic function measurement, and then if I want to measure all the way to the apex, I point all the way down towards the apex with my angle, so changing your angle with the parasternal short is extremely important to visualize all the different structures along the way. Let's go ahead and transition to the apical four-chamber view. There's a couple of things to keep in mind when doing an apical four-chamber view. First, it's one of the more challenging views to obtain, so this might be the one where you're going to have to turn the patient onto the left side. Another thing is if you're having a patient who has substantial breast tissue, you're going to want to lift the breast and scan in the axillary fold. Never scan over the breast. Another thing is sometimes you can attempt to find the point maximal impulse, or PMI, and that's generally the spot where you're going to want to place your probe. The apical four-chamber as a general view is quite good at visualizing all four chambers of the heart, evaluation of systolic function, as well as looking at the mitral and tricuspid valves. When I'm thinking about my apical four-chamber view, I'm generally going to be a little bit lateral to my midclavicular line, and I'm going to place my probe just inferior to the nipple. If you have a patient with really substantial systolic disease, their heart might be a little bit more laterally displaced, and you have to accompany that. Thinking about my patient here, I have my apical four-chamber. Generally, you're going to have to increase your depth as you're scanning. In this particular view, we can see the left ventricle, the left atrium, the right ventricle, and the right atrium. One of the confusing things is for this particular view, everything is switched. The left is on the right side, the right is on the left. For the apical four-chamber, this is actually a view that you may hear of two other views that come with apical in the name. This includes the apical five-chamber, as well as the apical two-chamber. To do an apical five-chamber, essentially what you're doing is taking the probe and pointing it a little bit more towards the patient's head, or in other words, more interiorly. So if I have my apical four-chamber right here, all I'm doing is dropping my probe a little bit, and that brings my aortic valve a little bit better into view. Similarly, if I want an apical two-chamber, which is something we can use to evaluate left ventricular systolic function, my orientation marker, which is now pointed to in a three o'clock position, is going to be rotated essentially 90 degrees up towards the patient's head. When I do that, I can see the left ventricle, and I also can see the aortic valve as well. This allows me for a very nice view of a patient's systolic function. Let's transition now to the subcostal view. The subcostal view is one of the most important views of bedside cardiac echo. It can be used to evaluate pericardial effusions, including tamponade. It's also quite good in code scenarios or cardiac compressions because it doesn't interfere with the person doing chest compressions. In terms of anatomical landmarks, you're going to palpate where the xiphoid process is. It can be very sensitive, so just palpate lightly as you're doing it. You're going to place your probe just beneath the xiphoid process. The marker of the probe is going to be pointed in a three o'clock position. Another thing to keep in mind with the subcostal view is oftentimes learners take this sort of underhand approach when they're doing it. I often find that taking an overhand approach, so grabbing the probe and almost viewing it like a remote control, can give you a little bit better of a scanning angle. So here I am feeling my xiphoid process. I'm having my probe. My marker is again pointed in this sort of three o'clock position. I might need just a little bit more gel, and I'm really dropping my probe so it's almost parallel with the patient's abdomen. Again, this is another view where you may need to increase the depth to be able to visualize all the anatomic structures. Here we can see the right atrium, the right ventricle, which is sometimes not always seen. You can also see the left atrium, the left ventricle, and to some extent the tricuspid and mitral valves. When I'm thinking about troubleshooting this particular view, it's often helpful to have the patient take a deep breath in as that pushes the heart a little bit better into view. So go ahead and take a deep breath in. Hold it. By doing it, it allows you to visualize the heart a little bit easier. Go ahead and exhale. There are three pathologies that we'll discuss in this video. These include systolic dysfunction, pericardial effusion, and right ventricular enlargement and systolic dysfunction. Let's first discuss left ventricular systolic dysfunction. There are three key portions when evaluating LV systolic dysfunction. These include endocardial excursion, myocardial thickening, and septal motion of the anterior leaf of the mitral valve, also known as EPSS. When you're thinking about endocardial excursion and myocardial thickening, you'll often need multiple views. One view is often not sufficient to evaluate the systolic function of the LV. When we're thinking about endocardial excursion, one thing to keep in mind is the endocardium may be mistaken for the ventricular wall or myocardium. And it's very important to track exactly how the endocardium is moving in multiple views. This is often a more qualitative assessment. You're essentially looking at the LV cavity and how much does it increase or decrease between systole and diastole. Generally speaking, you want that cavity to decrease about 50% or so in between diastole and systole. And this is a more qualitative assessment. If you want a more quantitative assessment, one common POCUS maneuver is evaluation of the E point septal separation, also known as EPSS. In this parasternal long image, we're showing the anterior leaflet of the mitral valve as it flaps between systole and diastole. EPSS is essentially a measurement of this anterior leaflet of the mitral valve as it moves close to the interventricular septum. If this valve leaflet fails to come within seven millimeters of their interventricular septum, this predicts a LV systolic function of less than 40% ejection fraction. It has a pretty good sensitivity of 70% and a specificity above 90%. There are several functional categories when we're thinking about estimating systolic function. Keep in mind that with point-of-care ultrasound, our goal is not to actually give you an exact number of ejection fraction. That's way beyond the scope of point-of-care ultrasound. That should be something that's done with formal echocardiography. Nonetheless, you can qualitatively assess how a patient's systolic function is. You can use categories such as hyperdynamic, normal, mildly reduced, or severely reduced, but keep in mind these are qualitative in nature. Here's a video of a parasternal long showing hyperdynamic systolic function. Here you can see the LV cavity completely collapsing during systole. You can also assess for hyperdynamic function in several other views, particularly the parasternal short, which we're showing here. Again, you see the LV cavity completely collapsing during systole. If you see a patient like this who is hypotensive or perhaps septic, this may be an indication that they need more aggressive fluid resuscitation. Thinking about reduced systolic function, again, it's a qualitative measurement. Here we're showing you a normal view of a parasternal long on the left and an abnormal parasternal long on the right. You can either use a more qualitative assessment or the EPSS, but what we're showing here is a little bit reduced ejection fraction. Here is a parasternal short from the same patient showing a mildly reduced ejection fraction and a normal on the left. Again, here is an apical four chamber with a normal on the left and an abnormal on the right. Again, you can see decreased excursion of the endocardium and that LV cavity is not quite shrinking 50%. Finally, just so you can see all the views, here is a subcostal view of a mildly reduced ejection fraction. Again, not able to see the entire LV cavity. There are also degrees that you can use so you can see normal or mildly reduced or severely reduced as we're showing here in these three videos. When it comes to assessing RV systolic dysfunction, there are two key views that can accomplish that. This includes the parasternal short and the apical four chamber. Thinking about the parasternal short, the RV is on the lateral side of the screen. One of the first clues that there may be RV systolic dysfunction is looking not so much at the size of the RV but how it's affecting the left ventricular systolic cavity. You often can see flattening of the inner ventricular septum as we're showing here when there's a very enlarged RV. To confirm this, you can use an apical four chamber view. When you're thinking about the apical four chamber, again you're assessing the size of the RV compared to the left ventricle. Generally, the RV is about two-thirds or less than two-thirds the size of the left ventricle. When you begin to see the RV approach two-thirds or even a one-to-one or greater than one-to-one ratio compared to the left ventricle, this is your first clue that you're dealing with RV enlargement, which also may be tied to RV systolic dysfunction. It's very hard to tease out on POCUS if the finding that you're observing is old or new. Certainly, evaluations for that do exist. That's generally beyond the scope of what we're trying to accomplish here. You should consider your entire clinical history, the patient in front of you, the physical examination, and expert consultation as needed for that. Another evaluation for RV systolic dysfunction includes a tricuspid annular plane systolic excursion, also known as TAPSE. In this apical four chamber view, we see the tricuspid valve on the left side of the screen. This tricuspid valve moves up and down during systole and diastole. You can actually measure how far this plane moves as an assessment of RV systolic function. If the TAPSE is generally less than 17 millimeters or 1.7 centimeters, this is considered abnormal and is an indication of abnormal RV systolic function. Finally, let's discuss pericardial effusion. There are two views you can use to assess for pericardial effusion. These include the peristernal long and the subcostal view, which tends to be the more sensitive view. First, thinking about the peristernal long, the pericardial effusion can be found in two places. It can track anteriorly towards the top of the image and more inferiorly towards the bottom of the image. One of the things that can often trick you is if a patient has a pleural effusion, you may mistake this for a pericardial effusion. What we're showing on the image on the left is a pericardial effusion and the image on the right is a pleural effusion. How I know the image on the left is a pericardial effusion is when I look inferiorly, I see that effusion tracks above the descending thoracic aorta, which we mark here. In contrast, in the image on the right, when I look at this particular image, the effusion or fluid is directly in contact with the descending thoracic aorta, which makes sense. If you think about the aorta, it's in the chest wall cavity. If there's fluid, it should be directly contacting it. So be sure to distinguish from a pericardial and pleural effusion using this technique of tracking the descending thoracic aorta relative to the fluid. Next, let's discuss the subcostal view or subxiphoid view for pericardial effusion. As I mentioned, this is one of the most sensitive views and generally you can get a quick assessment of the effusion by scanning the patient. Here we see an image of a pericardial effusion surrounding the entire heart. You may hear about assessments of right atrial collapse, right ventricular collapse. These are things that are a little bit more advanced and generally the assessment of pericardial tamponade or hemodynamic compromise is beyond the scope of POCUS. You should just incorporate POCUS into your clinical exam before determining if a fusion is clinically relevant or not.