Diagnosis of myocarditis and pericarditis (part 2)

Another test that we can order is a classic chest x-ray. A chest x-ray, we'll abbreviate that as a CXR. That's how we usually write it sometimes. So a chest x-ray, which isn't as safe as an echo, because this uses radiation. It uses radiation, and it's useful for giving us a static image of the heart. Static image of heart in the chest, and so we see it's sitting there relative to other anatomic borders, so here I've got a normal chest x-ray. You can see the heart just sort of outlined right here. I'm drawing it in for you. That's a normal heart that's sitting here in this little nob right there. It's the aortic nob, so that's kind of what it looks iike, and it sits here. These are your diaphragms down here. The diaphragm, and you can see the trachea, the clavicles, but notice this heart looks normal, and I say it's normal because when the heart is less than half the width right here, so it's less than half the width of this chest space, so I'll draw it right here. It starts here, and then it goes all the way to the end right there, so it's less than half that space, this space is called the media stinum, so it's less than half of the media stinum. That equals normal, and we're fine with that. So I'll write normal. So we say this is a normal chest x-ray. So this is a normal chest x-ray. And let's compare that to this guy. This is a chest x-ray of somebody with a pretty big pericardial effusion. A pericardial effusion, because this will give the heart an appearance like, and I'll label it up here, so this giant heart right there, which is definitely more than half of the media stinum, or half the width of this chest right here. It gives it a water bottle look, and that's pretty classic for a pericardial effusion. Water bottle appearance, and in fact, this could be so bad that this can cause what's referred to as, and I'll write it here, it could be so bad that this could lead to cardiac tamponade. Cardiac tamponade, which is the phenomenon where there's so much compression on the heart that it can't fill with blood anymore, and so cardiac tamponade has three cardinal signs that are associated with it. One is that you've got hypotension, or low blood pressure, because the heart can't pump blood out anymore because it can't even fill with any blood, so you've got low blood pressure, so hypotension is low blood pressure. You've also got what's called jugular vein distension. Jugular vein distension, which is when you've got these veins in your neck, so the internal jugular, the external jugular veins that are up in your neck, look bigger, or are distended, because these are the veins that are most directly going to return blood to the heart, and if the heart isn't able to fill with blood, because we've got such a huge effusion of either fluid or blood in the pericardial space compressing on the heart, then you're going to have backup of the blood to the jugular veins, and so you can see that in the neck, and then finally, number three, you would have distant heart sounds, so if you tried to listen over the chest with a stethoscope, for some reason, the heart would sound far away relative to what we usually hear when we listen with our stethoscope, so distant heart sounds, or distant lub dubs, and so this is actually a life threatening emergency that needs to be drained immediately, and this would require what's called a pericardiocentesis, and we'll talk about that in a separate video, but this water bottle appearance, I guess it's one of the older versions of water bottles that you would hold with your hand up here, is very classic for a big pericardial effusion. For myocarditis, on the other hand, so I'll write myocarditis down here, with like, a little star, myocarditis, this would appear with an enlarged heart, so enlarged heart, on chest x-ray, so a large heart on chest x-ray, and you might hear this term of cardiomegaly. Cardiomegaly, and that goes back to this rule I talked about above here. Cardiomegaly just means big heart, so megaly, mega, means larger, cardio means heart, so if it's bigger than half of the media stinum, then we've got cardiomegaly, and it's sort of a nonspecific thing, because we'll see cardiomegaly with other things that happen as well, not just myocarditis, but this is what you would look for on a chest x-ray if you're suspecting myocarditis. Alright, so let's move on. Another image that we can get is a computed tomography of the chest, so a computed tomography, so tomography, which is just the longhand version of saying a CT scan, or sometimes people refer to it as a cat scan, so a CT scan of the chest, so a CT scan of the chest would be helpful to see what's going on in the heart, so here we've got a CT of the chest with an axial cut, meaning it's a cut straight through somebody, as if you were trying to cut them like a carrot, and you can see the heart right here, but there's this very, very dark ring that's around the heart. This is a pericardial, I think you've guessed it, a pericardial effusion, so a pericardial effusion is seen right here, and it's pretty thick, and it looks like it's compressing the heart very strongly, so just to drive home some of the other concepts, when we have a CT scan, that uses more radiation, so it uses radiation more so than a chest x-ray. I think there's some calculation that it's over a hundred chest x-rays that you are doing to get a CT scan of the chest, but you can use other protocols to see, so you can see blood flow through your coronary vessels, so through the vessels that oxygenate, so there are multiple vessels, vessels that oxygenate the heart, so vessels that oxygenate the heart, and this gives a fairly good image, but sometimes people will consider this to be low resolution, low resolution relative to, say, a magnetic resonance image, so a magnetic resonance image, or, as you may know it better by, as an MRI, MRI of the chest, and so an MRI of the chest, if it's normal, should look like this, and you can definitely see the difference here. Look at how much smaller this heart is compared to this heart, and you can't see this very full pericardial space here in this normal heart, and I'll draw an arrow up here. This is a normal heart. Normal heart that we're looking at on a magnetic resonance image, and this doesn't use radiation, so no radiation, which is good, but we have to use a contrast material, so must use contrast, which is just a solution that we inject into veins to help us see things when we put a magnet over people, so we must use contrast that can, may hurt kidneys, so we have to use this contrast that can hurt kidneys function, so it may decrease your kidney function. Some people may be allergic to the contrast, so there are other things to worry about there, and this is also tons more expensive, so far more expensive than doing just your run-of-the-mill CT scan, but it gives you a better resolution picture, so better resolution. Some maybe argue the best resolution that you can get is with an MRI, but we usually don't order this unless we're concerned that maybe this person's a pregnant woman, maybe. You wouldn't want to give them that much radiation to a fetus that's still growing, or sometimes if you get a CT and it's not as very obviously conclusive as this image is here, we'd get an MRI to get a better idea of what's going on. Alright, so the last two types of tests we're going to talk about are somewhat related, and I'll start off by talking about what's called cardiac catheterization. Cardiac catheterization, and it's also sometimes called just a cath, or cardiac cath, and all this is, and I'll draw it on this lovely guy right here, so very great picture of a person that happens to have legs, and then their arms are right here, and as you know, their heart will be located about right there, and with cardiac catheterization, we enter through a vessel in the leg or the groin, and we follow them up through their vasculature to get up to the heart, so we use a vessel in the groin or the leg, use vessel in leg, let's say leg, to place a catheter, so place a catheter, which is just a small tube, place a catheter in the heart, and this catheter can do a whole bunch of things, so for one, it can measure pressure in the heart. If we have myocarditis, then we can measure pressure, so if we've got myocarditis, maybe there's less pressure in an effective chamber, so I'll write that here, myocarditis, would specifically have decreased pressure in the effected chamber, so in effected chamber, so in the effected chamber, and in pericarditis, if you've got very constrictive, so constrictive pericarditis, when you measure the pressure in constrictive pericarditis, what you would get is equal pressure, equal pressure in all chambers, so that would also be pretty diagnostic of constrictive pericarditis, or maybe the chest pain this patient is having isn't very characteristic of myocarditis or precordial chest pain of pericarditis, and you want to take a look at the blood vessels that give oxygen to the heart, so a cardiac cath can help you visualize, visualize vessels that deliver oxygen to your heart, so deliver O2 to the heart, because then you might just be having a heart attack, and that's why you're having chest pain, not myocarditis, or pericarditis, so I'll write on the side here, we can use this to rule out, rule out a heart attack, or a myocardial infarction, an MI, and then finally, the other thing that we can do with this catheter is what's referred to as an endomyocardial biopsy, an endomyocardial biopsy, which is perhaps the most invasive thing that you can do to come to an answer of what's going on. You literally take a sample, so you take a sample of the myocardium, the endomyocardium, actually, so I'll just write myocardium here, but you sample through the wall, so you can see where the endomyocardium stops and the myocardium begins, but it's just a piece. You don't take the whole thing, so you take a sample, and when you do this, I'll write up here, when you do this endomyocardial biopsy, you're trying to see if there's something going on in the myocardium, or even maybe you can take a look at the endocardium on the way, but you want to see if there's something irregular in the endomyocardium, sorry, the myocardium, so here's an endomyocardial biopsy right here, and down here you can notice this is normal myocardium, so that's normal myocardium, but that's a minority of the picture because what you see going on everywhere else is this infiltrate of immune cells, so this is what I mean when I said infiltrate, or invading, infiltrate, of immune cells that are in there causing inflammation, and this is due to viral myocarditis, and so we can do this biopsy to get a tissue sample to make sure that we've got myocarditis, and you can do the same and get a tissue sample of the pericardium to determine if you've got pericarditis, but this is a very invasive test, clearly, that you really would want to do only as a last resort. You don't want to take a piece of the heart away just to take a look and make a final diagnosis, especially if it's a disease that can be treated with some of the earlier tests that we've talked about here.