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Current time:0:00Total duration:9:11

Video transcript

so what you're looking at here is an ultrasound or what they call an echo of the heart and you can see the four different chambers and you'll see I've labeled the left ventricle and left atrium and what you'll notice is that the arrow is pointing to the valve in between the left ventricle and left atrium which is the mitral valve and that valve is actually not opening and so when that valve is really tight or doesn't open that is what's called mitral stenosis so like I said mitral stenosis is when you basically have a tight mitral valve now what I'm going to do is I'm going to draw a little set of lungs here and kind of briefly take you through how blood flows from the right heart through the lungs and then from the lungs and now I'm drawing back to the left heart and so those arrows are going to the pulmonary veins which go into the left atrium chumma marking off here LA and then the left ventricle LV and that that I'm circling right now is the mitral valve so the progression of blood is left atrium to left ventricle out the aorta and to the rest of the body and of course that blood into the left atrium like we just said was from the lungs now if the blood can't get from the left atrium to left ventricle it is going to back up in the left atrium and the lungs everything that was before it so let's talk about some of the causes of mitral stenosis what causes this valve to be tight well you can have what's called rheumatic fever or more specifically rheumatic heart disease when it affects the heart so another cause can actually be what's called endocarditis that's really an inflammation or an infection of the actual valve and these are some of the major causes of mitral stenosis there are obviously others but I want to keep you focused on the major ones so what causes rheumatic fever well it's actually pretty specific bacteria and it's part of a group called Group A streptococcus and so we can actually abbreviate that GA s Group A streptococcus and what we're really talking about here is a specific bacteria called streptococcus pyogenes this bacteria is actually what just causes strep throat so what will happen is someone gets a strep pyogenes infection or a pharyngitis meaning a throat infection and two to three weeks later if it's not treated correctly the person can actually present with some pain in their joints or arthralgias heart problems like a new heart murmur some skin problems and a bunch of other symptoms but for the most part the joints the skin and for our sake the heart problems are what we really want to focus on now the mechanism behind why this infection by this bacteria actually causes heart problems is called molecular mimicry and what happens is here if you see I draw this this antigen as green antigen as a triangle and then this red antibody and so the antigen is really going to be part of the bacteria that our body's immune system is going to respond to with an antibody but what happens is some of the antigens that this particular type of bug strep pyogenes puts out are actually very similar to some of the normal antigens or components of the tissue of the heart valves and so what can happen is when you actually form an antibody response to the particular infection those antibodies can actually go ahead and attack the heart the reason why you get all the other symptoms are because those antigens are also found in those parts of the body so that joints the skin and other things now the early lesion of rheumatic heart disease is mitral regurgitation but the late lesion meaning when you've had repeated bouts of this rheumatic heart disease or of this infection with strep pyogenes you actually get mitral stenosis which is what we're talking about now and mitral stenosis is characteristic for rheumatic heart disease so really what I'm trying to say is that a strep pyogenes infection itself the bacteria itself does not cause the heart problems it's actually our body's immune system responding to that infection that causes the heart problems so let's talk about endocarditis now which we said is an inflammation or infection of the heart valves now I'm going to write infective here because there are other rare more rare types of endocarditis but for the most part this is usually infective endocarditis when it has something to do with an infection either by a bacteria or a fungus or a virus and so there are kind of different ways that this can happen you can get an infection of a completely normal valve and the way that this happens is you actually have a bacteria that's really bad and so it's bad enough that it can infect a normal valve this is something like staph aureus now you can also have an infection of a previously damaged valve so if someone already had some damage to their valves a a bacteria that's not as bad may be able to actually cause this problem and this is often seen with normal flora in the mouth or bacteria that normally colonized the mouth such as strep viridans and that's actually a class of bacteria but these bacteria are just in the mouth and so this is actually why some people can get infections of their valves after having work done at the dentist because they actually become bacteremic or have these bacteria in their blood after their teeth and mouth have been manipulated and the last type is when someone has a prosthesis or a prosthetic valve has had a valve replacement in the past and these are character wrist quickly caused by staph epidermidis or staph epi these like to form little layers on prosthetic valves that allow them to survive and cause problems or endocarditis in addition the worst bacteria usually cause what we call acute bacterial endocarditis the less virulent bacteria usually cause what we call sub acute bacterial endocarditis and you should just remember that this infective endocarditis can be caused by bacteria viruses and a little bit more rare but can happen fungi now let's talk about the signs and symptoms associated with mitral stenosis now granted these may be based on the mechanism or how it was caused so if you have something like endocarditis as a result of an infection the person may have typical signs of an infection like fever chills an elevated white blood cell count stuff like that but for signs and symptoms of mitral stenosis specifically we're going to talk about signs and symptoms relating to the heart and cardiac physiology so if we go back to our drawing of the lungs which then return oxygenated blood to the left atrium which then goes through the mitral valve to the left ventricle and then to the body through the aorta we can see that if blood backs up you don't have as much output of blood to the body so you can get fatigued you can be short of breath because blood is backing up into the lungs you can have exercise intolerance because you can't get enough blood to the body to perfuse or to adequately oxygenate your tissues give you enough oxygen or you can have a call again because you're backing up blood into the lungs some signs that you may be able to see on echo or with your physical exam or maybe on an EKG would be signs of left atrial enlargement because if blood is backing up too into the left atrium you can have pulmonary congestion or edema and then you would also have a characteristic a skull Tottori finding or finding that you hear when you listen with the stethoscope and that would be a diastolic Rumble now there's also another characteristic finding that occurs just before that diastolic Rumble do you happen to remember what it is well it's an opening snap and if you forget any of these symptoms just remember that if you stop blood flow from the left atrium to left ventricle it backs up into the lungs and then you can kind of regenerate what kind of symptoms and signs that someone may present with when they have mitral stenosis