Cardiomyopathy: Definition and Types

Name: Cardiomyopathy: Definition and Types
Uploaded: 2022-04-04
Duration: 6 min 30 s
Description: The lecture Cardiomyopathy: Definition and Types by Richard Mitchell, MD, PhD is from the course Cardiology: Foundations.

by Richard Mitchell, MD, PhD

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

About the Lecture

The lecture Cardiomyopathy: Definition and Types by Richard Mitchell, MD, PhD is from the course Cardiology: Foundations.

Included Quiz Questions

What is cardiomyopathy?

Diseases that affect the heart muscle and decrease the ability to pump blood
Diseases that affect the heart valves and decrease the ability to pump blood
Diseases that affect the heart pericardium and restrict the ability to pump blood
Diseases that affect the electrical activity of the heart and decrease the ability to pump blood
Diseases within the mediastinum that restrict the ability to pump blood out of the heart

What is the most common form of cardiomyopathy?

Dilated cardiomyopathy
Restrictive cardiomyopathy
Hypertrophic cardiomyopathy
Arrhythmogenic right ventricular dysplasia
Takotsubo cardiomyopathy

Which of these conditions is most frequently associated with a genetic etiology?

Hypertrophic cardiomyopathy
Dilated cardiomyopathy
Restricted cardiomyopathy
Arrhythmogenic right ventricular dysplasia
Systolic cardiomyopathy

Author of lecture Cardiomyopathy: Definition and Types

Richard Mitchell, MD, PhD

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