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Mitral valve regurgitation and mitral valve prolapse

Video transcript

- So now let's talk about mitral regurgitation. So all that really means is that the mitral valve, the valve between the left atrium and left ventricle, is "floppy." So you'll see here that I'm going to mark off the LV or left ventricle, and then I'm going to show you the normal path it takes out of the aortic valve to the aorta and the rest of the body. But in mitral regurgitation, blood actually goes back into the left atrium. And then blood can actually back up from there into the pulmonary system. And so, you'll see I'm drawing these lines from the pulmonary veins that usually come from the lungs, but blood is going to get backed up from the left atrium to these pulmonary veins and back to the lungs that I'm drawing right here. So the normal path of blood would be from the left ventricle, to the aorta, and out to the rest of the body. But with mitral regurgitation, you actually have blood that goes from the left ventricle to the left atrium and then can back up in the lungs or pulmonary system, which can cause some symptoms. So now you'll see here is actually an echocardiogram of someone with mitral regurgitation, and what you'll notice is the blue flash back into the left atrium when the heart contracts. So normally when the heart contracts, blood should go out through the aorta, into the rest of the body, but here you'll see that blue flash, and that blue flash means that blood is actually coming back into the left atrium, indicating mitral regurgitation. So what I want to do is talk about the major causes of mitral regurgitation, and now there are a lot of them, so I'll try and focus on some of the major ones and then give you some other ones as well. So one of the first things is anything that leads to dilatation of the left ventricle or left ventricle dilatation can actually stretch the heart and cause the mitral valve to no longer come together appropriately, and that will lead to mitral regurgitation. So you'll see that I'm drawing here these arrows outward, kind of signifying enlargement of the left ventricle, and you'll notice that if that cavity enlarges, so does the mitral valve, and it can no longer close effectively. So things that lead to left ventricular dilatation would be a remodeling process, which is something that you would see occurring after a myocardial infarction, so remodeling post MI, and that's really just the heart taking on a different shape to try and compensate for problems after having a heart attack. Another thing would be dilated cardiomyopathy. And so, this is an inherent disease of the heart muscle that can cause the heart to become dilated, and this can actually be broken down into ischemic and nonischemic causes. So if someone has coronary artery disease for a while, this can actually happen, and the heart can become dilated to compensate for that, but it can also be a genetically-acquired disease or it can occur from things like alcohol or toxins. Another cause of mitral regurgitation would be rheumatic fever or rheumatic heart disease, and mitral regurgitation is actually the early lesion of rheumatic fever. Remember that the later lesion is mitral stenosis, and that occurs after you've had multiple bouts of rheumatic fever. Another cause is endocarditis. So you can get an infection of the valves, leading to a vegetation or something that builds up on the valve and doesn't allow it to close effectively. And another cause would be something like papillary muscle dysfunction or rupture, and this also goes along with chordae tendineae rupture or dysfunction, because those two are connected, and you'll see what I mean in a second. So let's scroll up a little bit, and we'll come back to that papillary muscle or chordae dysfunction. And the last cause would be calcification of the valve or around the valve that may not allow it to close effectively. So let's go back to the papillary muscle and chordae tendineae dysfunction so that I can show you what I mean here. So you'll see on this diagram, that's really kind of a cut through the left ventricle, that the blue things are the papillary muscles, and the gray strings are the chordae tendineae. And so, these are really just an anchoring system for the valves, to make sure that they can open and close effectively. And I just realized that I spelled tendineae wrong, so I'll fix that right now. And you can see that the chordae are actually attached to the mitral valve. And let me just label these things for you. So left atrium here and aorta here, and we're in the left ventricle there. So you can see if a papillary muscle ruptures or one of the chordae ruptures that you'll actually have a leaflet of the valve that may just be flailing around. And so, the mechanism of opening and closing becomes pretty inefficient. So now let's talk about some signs and symptoms of mitral regurgitation. So you can actually have acute mitral regurgitation or chronic mitral regurgitation, which is more what we're talking about here, but an important cause of an acute mitral regurgitation, where the heart has no time to compensate, would be something like a papillary muscle rupture, and this could occur after something like a heart attack. For chronic mitral regurgitation, this would be something along the lines of a dilated left ventricle due to chronic coronary artery disease. So you'll see I write dilated ischemic cardiomyopathy there. Now, back to the papillary muscle rupture. If something like this happens acutely, the heart has no time to adapt to these pressure changes, and so you get what you call flash pulmonary edema or acute pulmonary edema, and the person may go into congestive heart failure. And so, this is a medical emergency, and this needs to be treated right away. Now, for something like the dilated ischemic cardiomyopathy, or any other major cause of chronic mitral regurgitation, where there's been time to adjust to these pressures, you'll see things like fatigue and shortness of breath and maybe some pulmonary congestion or edema but not this rapidly developing type that we saw in the acute mitral regurgitation. Other things that you may be able to see are signs of left atrial enlargement, which you may be able to see on an EKG or in an echo, and then on auscultation, or when you listen with your stethoscope, you should be able to hear a holosystolic murmur at the apex or in the mitral region, which is in the fifth intercostal space in the midclavicular line. So now let's talk about mitral valve prolapse. So mitral valve prolapse is when the valve actually billows or bulges into the left atrium. And mitral valve prolapse itself actually doesn't usually lead to a murmur, but if the valve then becomes dysfunctional, you can actually get the murmur of mitral regurgitation. So if you notice I'm going to zoom into the heart down here, and you'll see I'm drawing the chordae attached to the papillary muscles, and then I'm going to erase one of the valves here, one of the normal valves, and show you what it looks like when mitral valve prolapse has occurred. And so, here you'll see that little hump, and it's like this valve has kind of ballooned into the left atrium. And I'm drawing an arrow to that now. Now if you'll see here, you can see I've labeled the left atrium, the left ventricle, and the aorta, and during systole, when the left ventricle contracts and blood should be going out of the aorta, you'll see that one of the cusps of the mitral valve actually comes into the left atrium a little bit, and you can see I put an arrow next to that. So let's talk about the causes of mitral valve prolapse. The major causes, one of them is actually idiopathic, meaning we don't really know what causes it. Another cause is when this mitral valve prolapse actually occurs secondary to a connective tissue disorder, and a connective tissue disorder means exactly what it sounds like. You have a problem in making proper connective tissues which make up some of your arteries and some of the tissue in the body. And so, certain conditions like Marfan syndrome or Ehlers-Danlos actually can cause mitral valve prolapse. So some signs and symptoms of mitral valve prolapse. Well, this is kind of a tough one. So many people are asymptomatic and may just have been told by their doctor at one point that they had a funny sound when the doctor listened to their heart. But there's another group of people that actually have some symptoms that the medical community has labeled the mitral valve prolapse syndrome. And there's some debate as to whether or not this is actually a real syndrome, but what this consists of is some atypical chest pain, meaning it's not anginal in character, meaning it's not the typical pain that you get with coronary artery disease or blockages of the arteries. These people also complain of palpitations or the feeling that their heart is beating either extra fast or extra forceful, and then also some shortness of breath and some dizziness or syncope. And syncope is just fainting. And the way that we can identify this condition with auscultation is that we hear a mid systolic click, and then if it has progressed into valve dysfunction, you'll actually hear the murmur of mitral regurgitation following this mid systolic click, but the mid systolic click is a classic sign for mitral valve prolapse. And one other important thing to know is that mitral valve prolapse actually puts you at an increased risk for a couple of things, such as infective endocarditis. So remember, this valve is not totally normal, and so it's slightly more likely that bacteria can actually colonize and infect this valve. In addition, mitral valve prolapse may predispose these people to certain arrhythmias, and then, like we said before, it can actually progress to mitral regurgitation. And so, that can cause some more problems.