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Current time:0:00Total duration:13:43

Diagnosis of myocarditis and pericarditis (part 2)

Video transcript

another test that we can order is a classic chest x-ray a chest x-ray abbreviate that as a CX R 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 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 and this little knob right there is the aortic knob so that's kind of what it looks like as 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 of that space this space is called the mediastinum so it's less than half of the mediastinum 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 mediastinum 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 appear in fact this could be so bad that this can cause what's referred to as and I'll write it here it's 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 I hypo tension is low blood pressure you've also got what's called jugular 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 try 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 megali mega means larger cardio means heart so if it's bigger than half of the mediastinum then we've got cardiomegaly and it's sort of a nonspecific thing because we'll see cardiomegaly with other things that happen is well not just myocarditis but this is what you would look for on a chest x-ray if you're suspecting myocarditis all right so then 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 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 it's 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 and I think you 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'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 magnetic resonance image so a magnetic resonance image or as you may know it better buy 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 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 may 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 this person is 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 images here we'd get an MRI to get a better idea of what's going on all right 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 catheterisation cardiac catheterisation and it also 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 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 vessel in the LaGrone 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 you can measure pressures 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 affected chamber so in affected chamber so in the affected 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 o to 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 and MI and then finally the other thing that we can do with this catheter is what's referred to as an endo myocardial endomyocardial biopsy 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 endo myocardium actually so I'll just write myocardium here but you sample through the wall so you can see where the endo myocardium 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 all right 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 endo myocardium 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 the disease that can be treated with some of the earlier tests that we've talked about here