Diseases of the Heart Muscle – Cardiomyopathy

00:08 In this section, we will talk about heart muscle diseases, otherwise known as cardiomyopathies.

00:15 The definition of “cardiomyopathy” is entailed in the name itself: “cardio” meaning “heart”, “myo” meaning “muscle” and “opathy” meaning “a disease”.

00:28 All of these terms come from the Latin and Greek and they mean “heart muscle disease”.

00:34 Cardiomyopathy is a disease that primarily affects the heart muscle.

00:40 We’ve talked about diseases that affect the blood vessels, we’ve talked about diseases that affect the electrical system, and we’ll be talking more about that in a later lecture.

00:50 But, this is a series of diseases that affect the heart muscle.

00:55 Some of them are primary diseases that are genetic and develop because of an abnormality in the DNA code, and some of them are acquired from environmental circumstances.

01:07 And we’re going to look at all of them as we go through this talk.

01:11 Cardiomyopathy often gains attention in the news media.

01:16 Why? Because one form of cardiomyopathy, hypertrophic cardiomyopathy, is the commonest cause of sudden death in athletes.

01:26 And of course, this is a catastrophic event.

01:28 A young, healthy, vigorous person suddenly falls to the field and, if not resuscitated, actually dies.

01:38 We’ll talk about hypertrophic cardiomyopathy.

01:40 Fortunately, most people with it do not stand a chance of sudden death, but there is a small group of individuals with this disease in whom sudden death is a high risk.

01:51 And we’ll talk about that during this session.

01:54 So, let’s go over something about cardiomyopathy, in general.

01:59 First of all, it is the second commonest cause of sudden death after ischemic heart disease, but of course, there are far fewer patients with cardiomyopathy, so far fewer individuals with sudden death compared to ischemic heart disease.

02:15 There is, very severe forms of cardiomyopathy and less severe forms.

02:21 One form called “dilated cardiomyopathy” has a poor prognosis.

02:26 It means that the patient often will have a survival that can be measured sometimes in months or years and is associated with severe heart failure.

02:36 And we’re going to go over this form in considerable detail.

02:41 In general, there are two types of cardiomyopathy.

02:44 There is the primary type.

02:46 This is the genetic type, usually, or it’s a type that we don’t understand what the cause is, but we think it may be genetic.

02:56 And then there is the secondary type, where we know what caused it.

03:00 For example, a viral infection or a drug.

03:04 We’ll talk a little bit about the drugs.

03:06 Some of the chemotherapy drugs that are used, for example, in different kinds of cancer, for example, breast cancer can damage the heart and lead to a secondary cardiomyopathy and heart failure.

03:19 So, the American Heart Association defines cardiomyopathy as you see here.

03:27 Primarily, it is a disease of muscle.

03:30 They distinguish the primary forms from the secondary forms, and you can see in the little diagram on the side, the primary forms and the secondary forms, and some of the reasons for the secondary forms.

03:43 This little diagram is an introduction to what we’re going to talk about for the next 30 minutes.

03:49 The little diagram is a cross-section of the left and right ventricle.

03:53 At the top, you see the normal thickness of the right ventricle, a circular chamber, more shaped like the piston in a car motor.

04:02 And then you see the triangular-shaped, thinner-walled right ventricle shaped more like the bellows that one uses to build a fire in the fireplace or the blacksmith uses to increase the heat of his fire.

04:17 You can see to the left there is the findings on the cross-section of a hypertrophic cardiomyopathy.

04:25 “Hypertrophic” means “increased in size and volume”.

04:30 And you can see that the wall of the left ventricle is markedly thickened and both during systole and during diastole.

04:38 As you move across into the middle zone, the middle one on the second line is the dilated cardiomyopathy.

04:45 You see the left ventricle is increased in size, and the wall is somewhat thinned.

04:50 There is a form to the right, which is a restrictive cardiomyopathy, and also, below that, you see restrictive cardiomyopathy as well as a so called right ventricular primary cardiomyopathy.

05:10 We’ll talk about those.

05:11 Those are quite rare, the latter two, the right ventricular and the restrictive, but we’ll talk about them in a little more detail, although they really are quite uncommon.

05:22 The commonest forms are hypertrophic and dilated.

05:25 And so, we’re going to spend most of the time talking about that.

05:29 Just as in coronary disease and atherosclerosis, there are a number of demographic factors which have been associated with the development of cardiomyopathy - uncontrolled high blood pressure, some small number of women who have had a pregnancy will develop a so-called postpartum cardiomyopathy, viral infections, excessive use of alcohol, there are a number of inherited forms and it turns out that in the United States, African-Americans of both genders are at increased risk for cardiomyopathy.

06:07 Again, probably a genetic, what we call polymorphism - that is, something, a small change in the DNA actually predisposes them to develop heart muscle disease.