00:01
<b>Welcome.</b>
<b>We're going to talk about a rather</b>
<b>large but very important topic</b>
<b>of basic heart muscle disease, or cardiomyopathy.</b>
<b>We're going to do an overview, and then we</b>
<b>will talk pretty much in three little bins,</b>
<b>or three larger bins about the</b>
<b>various forms of cardiomyopathy.</b>
<b>While we are understanding more</b>
<b>and more of the genetic basis</b>
<b>underlying many of these</b>
<b>intrinsic heart muscle diseases,</b>
<b>it's still best to think about them</b>
<b>in terms of their pathophysiology.</b>
<b>So we will talk about a dilated or</b>
<b>globoid, or kind of floppy heart.</b>
<b>We'll talk about a very hyper dynamic</b>
<b>heart, that's hypertrophic cardiomyopathy.</b>
<b>And then we will talk about restrictive</b>
<b>cardiomyopathy, which is a stiff heart.</b>
<b>So let's start with a cardiomyopathy overview.</b>
<b>As I've already stated, cardiomyopathy is basically</b>
<b>a group of diseases that affect the heart muscle,</b>
<b>and decrease its ability to pump blood.</b>
<b>And that may be because it doesn't fill very</b>
<b>well, or because it doesn't pump very well.</b>
<b>And either one of those will lead</b>
<b>to the overall effect that there's</b>
<b>diminished ability to pump blood</b>
<b>systemically to all the organs of the body.</b>
<b>There can be primary causes of cardiomyopathy</b>
<b>intrinsic to the cardiac muscle.</b>
<b>There may be secondary forms due to diseases</b>
<b>of other kinds that affect the cardiac muscle.</b>
<b>We're going to use this kind</b>
<b>of schematic to help understand</b>
<b>the various forms of cardiomyopathy or the types.</b>
<b>Looking at the normal heart, you</b>
<b>can see them we've emphasized mainly</b>
<b>the left ventricle and the left</b>
<b>atrium and the aorta but you can also</b>
<b>in some of the images that we're going to</b>
<b>show affect the right ventricle as well.</b>
<b>But the normal heart has normal closure</b>
<b>valves, normal sized left atrium,</b>
<b>normal sized left ventricle cavity, normal</b>
<b>thickness of the myocardium and the left ventricle.</b>
<b>In a dilated cardiomyopathy, we're gonna</b>
<b>see kind of a globoid dilation of the heart.</b>
<b>This is actually the most</b>
<b>common cause of cardiomyopathy.</b>
<b>Roughly 85 to 90% of cases are</b>
<b>going to be dilated cardiomyopathy.</b>
<b>And along with this dilation of the chamber,</b>
<b>you can see that we're pulling those</b>
<b>papillary muscles a little bit apart,</b>
<b>which are tugging on the chordae tendineae,</b>
<b>which are opening the mitral valve, and</b>
<b>so there's marked left atrial dilation.</b>
<b>Those are all part and parcel</b>
<b>of a dilated cardiomyopathy.</b>
<b>This also includes arrythmogenic</b>
<b>cardiomyopathy previously called</b>
<b>arrythmogenic right ventricular cardiomyopathy,</b>
<b>because it predominantly</b>
<b>affects the right ventricle.</b>
<b>The important point about this is that</b>
<b>it is a form of dilated cardiomyopathy.</b>
<b>We'll cover it more later,</b>
<b>so just keep that in mind.</b>
<b>The flip side of the coin is</b>
<b>hypertrophic cardiomyopathy.</b>
<b>Hypertrophic cardiomyopathy is a thickened</b>
<b>ventricle with a hyperdynamic heart,</b>
<b>so there's more cardiac muscle mass.</b>
<b>The outcome though, however, because of</b>
<b>obstruction to the left ventricular outflow</b>
<b>due to the thickness of the</b>
<b>interventricular septum myocardium,</b>
<b>can also lead to left atrial enlargement.</b>
<b>So you can have some of the</b>
<b>same general geographic effects.</b>
<b>And then there's restrictive cardiomyopathy where</b>
<b>the chambers of the heart look pretty normal,</b>
<b>the thickness of the wall looks pretty normal.</b>
<b>But because we have infiltrated the</b>
<b>myocytes, or the the myocardium,</b>
<b>with various things like fibrous</b>
<b>connective tissue, or amyloid,</b>
<b>the walls are stiff so they don't relax very well.</b>
<b>We're going to cover each of these in turn</b>
<b>these kind of basic pathophysiologic forms -</b>
<b>dilated, hypertrophic, restrictive, and talk</b>
<b>about the etiologies and the consequences.</b>
<b>Let's start first with dilated cardiomyopathy.</b>
<b>In general, split about 50/50.</b>
<b>The numbers change because we're</b>
<b>finding more genetic causes,</b>
<b>but at roughly 50/50 genetic</b>
<b>causes and non-genetic causes.</b>
<b>These dilated cardiomyopathies cause systolic</b>
<b>dysfunction, so they don't squeeze very well.</b>
<b>They actually fill pretty well, they're</b>
<b>pretty floppy, so they fill okay,</b>
<b>they just don't squeeze the blood out so</b>
<b>ejection fractions will be markedly diminished.</b>
<b>In hypertrophic cardiomyopathy, we know it's</b>
<b>about 100% of cases have a genetic cause</b>
<b>and we understand the vast majority of those.</b>
<b>In this case, it's not systolic</b>
<b>dysfunction, they squeeze great.</b>
<b>In fact, they squeeze too well,</b>
<b>but they don't relax very well.</b>
<b>So they're like hard driving</b>
<b>medical students around the world.</b>
<b>They work really hard and</b>
<b>they don't relax very well.</b>
<b>So it's diastolic dysfunction.</b>
<b>And then a restrictive cardiomyopathy.</b>
<b>As I've already stated, it's associated with</b>
<b>some systemic disorders, or it may be idiopathic.</b>
<b>And the fundamental problem is that it's</b>
<b>diastolic dysfunction, it's a stiff heart.</b>
<b>There's not a lot of muscle there,</b>
<b>or not excessive increases in muscle,</b>
<b>but it's stiff, and therefore</b>
<b>you have diastolic dysfunction.</b>
<b>It doesn't relax to fill very well.</b>
<b>In all the cases, whether it's</b>
<b>dilated, hypertrophic or restrictive,</b>
<b>the clinical presentations</b>
<b>are pretty much the same.</b>
<b>It's heart failure, we have inadequate pump</b>
<b>function to perfuse the rest of the body.</b>
<b>And as the heart either dilates, and</b>
<b>the valves fail, or as we have increased</b>
<b>squeezing with poor relaxation, we tend</b>
<b>to get regurgitant flow into the atrium,</b>
<b>We get left atrial enlargement</b>
<b>that leads to atrial fibrillation.</b>
<b>A combination of atrial fibrillation,</b>
<b>a kind of quivering left atrium,</b>
<b>and diminished flow through that left</b>
<b>atrium with a dilated left atrium</b>
<b>is going to make that portion of</b>
<b>the heart prone to forming thrombi,</b>
<b>so patients can also present with</b>
<b>stroke and with sudden cardiac death</b>
<b>due to either embolization</b>
<b>or to sudden arrhythmic events.</b>
<b>So the final consequences of all</b>
<b>these are pretty much the same.</b>
<b>How we get there in each of</b>
<b>them is a little bit different.</b>