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.