00:01
The final category of cardiomyopathy
is restrictive cardiomyopathy.
00:05
Restrictive cardiomyopathies are fundamentally
a diastolic dysfunction cardiomyopathy.
00:12
So in some respects, it share some of the
features with hypertrophic cardiomyopathy.
00:16
Overall, it is the least common of all three
types - dilated, hypertrophic and restrictive,
about 5% overall, or less.
00:26
What's been indicated on the schematic
is that the myocardium has been
partially replaced with something
else that isn't myocardium.
00:35
Fundamentally, this makes the wall less able
to dilate and fill, it makes it stiffer.
00:42
As a result of that, we do not have
normal filling of the left ventricle.
00:48
Sitting behind the left ventricle, his left
atrium, it's trying to squeeze blood into that
very stiff left ventricle and
it's not being successful.
00:56
So you have a volume overload leading
to dilation of the left atrium.
01:01
So in words, what I just said, you get
stiffening of the ventricular wall,
loss of myocardial flexibility, contractile force,
due to infiltration by abnormal tissues.
01:13
This can also occur not only due to the
infiltration with things like amyloid,
but also due to scarring of the pericardium.
01:22
So that would be a constructive cardiomyopathy
if we have fibrous connective tissue,
completely surrounding the heart that will
also keep the heart from being able to fill
during diastole.
01:33
And we'll have a similar
physiologic manifestation.
01:39
What are the causes?
Like everything in medicine, idiopathic is always
on your differential, meaning we don't know.
01:46
I suspect, as we get smarter and more
clever and are able to do deep sequencing,
we'll find more genetic basis for this.
01:55
There are various familiar forms
of restrictive cardiomyopathy
with known genetic mutations,
we'll briefly touch on those.
02:04
But most commonly, as causes,
restrictive cardiomyopathy
are the deposition of other non-cardiac proteins.
02:14
Chief amongst these is amyloid.
02:16
We'll talk more about that.
02:17
But sarcoid can also be a cause
of restricted cardiomyopathy.
02:21
If you've been paying attention, you're saying,
'Wait, you said sarcoid could
be dilated cardiomyopathy?
Yep, it can.
02:27
In some cases, because of the
scarring and the deposition,
you can also get a restrictive cardiomyopathy.
02:33
Hemochromatosis can also cause
a restrictive cardiomyopathy.
02:38
Initially, it will prominently
present as a dilated cardiomyopathy
due to apoptosis due to iron overload,
reactive oxygen species, et cetera.
02:47
But with time, you can get fibrosis so it
can become a restrictive cardiomyopathy,
And then Loeffler's endomyocarditis.
02:55
A rare but interesting form of restrictive
cardiomyopathy due to thickening fibrosis
of the endocardial layer.
03:05
In restricted cardiomyopathy, fundamentally,
there's some increased extracellular material
not otherwise specified in the myocardium.
03:13
Or you can have endocardial scarring, the lining
of the ventricular walls become fibrotic.
03:21
That will also keep the wall from
being able to fill during diastole.
03:26
You have decreased diastolic relaxation,
and decreased ventricular filling,
the consequences are due to
a stiffened ventricular wall.
03:36
And upstream, we're going to get atrial dilation.
03:39
That poor atrium, left atrium is trying to squeeze
blood into that stiff left ventricles like,
can't get anywhere, so you get atrial dilation..
03:48
With that happening, you can
get systemic venous congestion.
03:53
Basically, the increased pressure
and volume overload in the atrium
reflects back through the lungs
and into the systemic vasculature.
04:00
So you can see left heart failure, right
heart failure, biventricular failure.
04:07
There's also diminished cardiac output.
04:09
Clearly, you're not filling the ventricles, so
you're not getting the maximum amount of volume out
so patients can also present with hypotension.
04:18
The configuration is different than what we saw
in dilated or in hypertrophic cardiomyopathy.
04:23
This is not a floppy heart.
04:24
This is not a muscular heart.
04:26
This is kind of a normal-sized chamber, but the
nature of what's in the walls makes it stiff.
04:34
The atria will dilate up, and that's an important
component of a restrictive cardiomyopathy.
04:41
This is just showing you an example
of restrictive cardiomyopathy
due more to the endocardial fibrosis.
04:48
The wall may actually not have much
in the way of extracellular material,
but the endocardium being fibrosed
limits the movement of that wall.
05:00
What are the signs and symptoms?
Well, you can predict based on what
you now know about the pathophysiology.
05:05
You have poor forward flow so patients are
dizzy, lightheaded, they may have frank syncope.
05:10
They may have left heart
failure, so they are dyspneic.
05:14
You can also, as part of that dyspnea
and the pulmonary edema have rales.
05:19
You can also have diminished flow into
the coronary artery, so you have angina
and you can have arrhythmias.
05:26
So all the things again, kind of just because
you have this doesn't necessarily mean
that you have a restrictive cardiomyopathy.
05:33
Clearly it could be dilated cardiomyopathy,
hypertrophic cardiomyopathy or some other cause.
05:40
But these are signs and
symptoms associated with that.
05:43
And you may also see a systolic heart murmur.
05:47
So abnormal flow through the valve
because of poor filling of the heart.