heart disease. Important for us to take a
look at the following table, quite. So the
patient has now moved on from unstable angina.
Unfortunately has now experience the myocardial
infarction, an MI. How do you know that?
Patient says I have chest pain, has tachycardia,
diaphoresis. This chest pain is radiating
where? Up into the left shoulder as maybe
moving up into the jaw. Substernal chest pain,
is it not right? Take a look at the cardiac
enzymes, you find troponin I to be elevated.
Why is that your gold standard because within
24 hours, it is elevated and how long does
it last, troponin I? About one week. Keep it
simple, okay. So therefore, it is quite difficult
for you to miss your patient having a myocardial
infarction with troponin I and you shall see
that in a second. So now what are you doing
here? The important points of changes in myocardial
infarction. It is 0 to 24 hours gross changes
like microscopy and then complications. 0 to
24 hours. Have occlusion of an artery,
infarct. You have dark mottling, that's what you are
looking at and pale with the area because it just
underwent what? Necrosis. What kind please?
From basic pathology, it is a coagulant necrosis.
What kind of infarct is this? A pale or hemorrhagic
infarct. It is a pale infarct. Things that we have
already referred to. So let us begin at the
top. Coagulant necrosis, what then happened?
There was reversible injury at first, wasn't
there? There was ischemia taking place, lack
of oxygen. If there is no oxygen, then what
kind of glycolysis do you have? Lack of oxygen,
anaerobic glycolysis or are you going to produce
as much pyruvate? No. You're going to produce more lactic
acid? Sure you will. Anaerobic glycolysis,
lactic acid in that area. What happens to
your pH? It decreases. Alright. So what happens to
your enzymes? Enzymes in environment where is acidic,
is it more active or less active? Do not
memorize this. What kind of necrosis? Coagulative
necrosis right. What does coagulative mean?
Preservation of your architecture. How is
it that your preservation of your architecture?
The enzymes aren’t working, is that clear?
Gross changes, pale. Why is it a pale type of
necrosis or pale type of infarct? Because there
is only one blood supply to that particular
tissue or organ. Light microscopy, early coagulant
necrosis you know preservation of your architecture.
Wavy fibers. So what are you seeing here in
this schematic is cardiomyocytes and they
should be nice and parallel normally. Remember
this from histology. You have seen this before
and the cardiomyocytes should be nice and
parallel, should be nice and straight and
they should have intercalated discs. Remember?
And those intercalated discs are your gap
junctions. So that your heart can beat as
one unit called syncytium. Okay. So what then happens here
earlier on 0 to 24 hours, you might get wavy
fibers. You see that. It is wavy. It shouldn't
be like that. Early changes. Next this is
an acute MI. So any type of acute inflammatory
response, what are you going to bring in?
Neutrophils, good. Next, now things we will
talk about later is that remember, management.
What are you trying to do? You're trying to bust that
clot. If you want to bust a clot, what might
you introduce? Re-perfusion injury. We will
talk about this later. And when there is re-perfusion
injury, you might then introduce tons of calcium.
You see that? Tons of calcium coming in,
and therefore causing quite a bit of damage
as we shall see, complications. We have
ventricular arrhythmias, may be heart failure,
worst case scenario when you have arrhythmia,
what may then happen? The heart might just stop,
cardiac arrest. Welcome to cardiogenic shock.
Let us continue. 1 to 3 days, if it is 1 to 3 days
now what happens to this necrosis? It is rather
extensive. Now you have lots of neutrophils
coming in and now after three days, what kind
of pericarditis might this be? This is three
days, so therefore this is fibrinous pericarditis.
Versus what other type of pericarditis might
you see please in pathology? Dressler's, right.
Dressler's pericarditis and as we go through
cardiology, we will take a look at the difference
in timeline between fibrinous pericarditis,
which will be days, versus Dressler, which
could be three weeks to a month or perhaps
even a little bit more, but not within three
days. It is that clear. That must be understood
and if your patient does have pericarditis,
then what happens? You lean forward, I feel
so much better; you lean back, oh my goodness
gracious you are creating friction, pericarditis.
And you do inspiration, that makes it worse,
doesn't it? Welcome to pericarditis in general.
Things that you guys know, but just to make sure
that we put things into context. Let us go
to 3 to 14 days and now we are beyond three days.
We are getting into weeks. So now the neutrophils
are going to be replaced by whom? Macrophages
and take a look at the cartoon there. That
is hyperemic. What does that mean? That means
after three days, the heart and the tissue
is trying to recover. Then necrosis is irreversible.
What about the surrounding tissue? Well you can
have a rim of hyperemia, is that clear? That
is within two weeks. Rim of hyperemia. That
is the most important point there. Macrophages
are coming in. Now let us go into complications
now. With this, I am going to walk you through
this as well. So now when you think about
repair process. Close your eyes. Think about
repair process okay. Now you think about
repair process, then should you bringing in collagen?
Sure. Who lays down that collagen? What is the
name of that cell? Come on. Good. Fibroblast. And you
are going to have a scar and is this scar
always a good thing? Not in the heart. So
that if you have a scar formation taking place in
the heart, what happens to the conduction
system? That could be affected. Welcome to
arrhythmia. Next, what if we have fibrosis
and that scar wasn't strong, what then happens?
I want to you think about the ventricle and let
us say that the ventricular wall with the
scar is quite weak. Are you with me? So with all that pressure,
what is going to happen? A ventricular aneurysm,
right. With that aneurysm, what does that
mean? Ballooning. At some point, what may
then happen to the wall? It might give away.
What is that called? Rupture. Okay, now let me ask
you something. When you have rupture taking
place, how quickly is that fluid building up in
the pericardium? Once again, you walk me through
this, how quickly is that fluid accumulating in
pericardial cavity? Like that. I don't care
if it is even a measly 200 milliliters, a little amount
of fluid rapidly accumulating in the pericardial
cavity, by definition, is what? Good. Pericardial
tamponade. Are you seeing this? Good. Let us
continue. There might be papillary muscle
rupture. At some point when your heart starts
dying, then what happens to the mitral root
or even the aortic root? It might then become
expanded. Welcome to what please? Valvular
heart disease. What kind? If you have root
dilation, don’t memorize it. Root dilation
what is that going to give you? Regurgitation
type of valvular heart diseases, isn't it?
Let us continue. Now next you have what is
known as your pseudoaneurysm and you're worried about
there once again ruptures, what we have talked about.
It is macrophage-mediated structural degradation.
All of these things at some point in time
may give you serious complications. Let us
going to weeks now. Weeks we have scar formation.
We have lots of collagen as such and you're paying
attention at Dressler syndrome. So what is
the difference between fibrinous and Dressler?
They are both pericarditis, fibrinous pericarditis
would be the normal type of inflammatory process
that you might see within three days. However,
if you have an autoimmune response for whatever
reason and you might then result in pericarditis,
weeks to months later, then you are thinking
about Dressler. It is that simple and it is
that clear. These are some of the most important
changes that you want to pay attention to
when you are dealing with myocardial infarction
in terms of hours, days, weeks and months.
You pay attention to these tables. You are
in fantastic shape.