Stenosis, ischemia and heart failure | Miscellaneous | Heatlh & Medicine | Khan Academy
Stenosis, ischemia and heart failure | Miscellaneous | Heatlh & Medicine | Khan Academy
Clarifying a bunch of medical terms around heart disease. Created by Sal Khan.
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Content
0.5 -> As someone who's married to a
doctor, in the medical field,
4.62 -> I think it's pretty important
to have a precise understanding
7.43 -> of what the words mean, just
so that you can understand what
9.53 -> people are talking about if
either you are a health care
11.863 -> professional or if some health
care professional is talking
15.15 -> to you, as my wife does
when, well, sometimes does,
18.11 -> when she comes home from work.
19.96 -> So let's get a little bit more
precise with some of the words
22.79 -> we've been talking about,
especially relative to heart
25.05 -> disease and heart failure
and all of the rest.
27.85 -> So let's say this is an artery.
29.55 -> The blood is flowing
in that direction.
31.23 -> I'll show the artery
branching off.
33.06 -> It thins as it goes
farther and farther along.
35.94 -> So this right here is an artery.
37.6 -> And let me draw a
plaque in that artery.
39.87 -> And we've been
studying these plaques
42.59 -> in arteries since the
video on heart attacks.
46.28 -> So let's say that this is a
bunch of white blood cells
50.75 -> and lipid material.
52.39 -> So it's cholesterol and
fats and all the rest.
55.97 -> Now a word that you might hear
in kind of a medical context
59.37 -> is stenosis.
64.8 -> And the word "stenosis" just
refers to the narrowing,
68.02 -> usually of a blood vessel.
69.48 -> So this right here, this blood
vessel has been narrowed.
72.83 -> So this right over
here is stenosis.
75.04 -> It's been narrowed
by this plaque.
77.06 -> It can also refer
to the narrowing
78.92 -> of kind of any type
of tubular structure.
81.05 -> So if you have any type of kind
of pipe in a biological system
85 -> and it gets narrow, they
might refer to stenosis there.
87.35 -> But usually they're talking
about a blood vessel.
89.391 -> In this example that I've
drawn here it's an artery.
92.39 -> So the stenosis is
just the narrowing.
97.8 -> Now once the blood
vessel is narrowed,
102.32 -> that restricts the blood supply.
104.06 -> So you aren't able to get
as much blood through it.
109.86 -> So the blood supply
is restricted.
112.5 -> So restricted blood supply.
117.62 -> Put the I there.
118.56 -> Restricted blood supply.
121 -> This restriction
of a blood supply
124.05 -> that usually leads
to some type of loss
125.98 -> of function, that's called-- so
this restricted blood supply--
130.38 -> this is called ischemia.
132.44 -> Another fancy word,
but it literally just
134.15 -> means restricted blood supply.
136.72 -> Ischemia.
138.84 -> Now if you have stenosis in one
of your blood vessels, in one
142.67 -> of your arteries, and it
restricts your blood supply.
146.11 -> So it leads to ischemia.
149.99 -> Let's say let me draw a
muscle cell farther over here.
152.81 -> Let's say this is a coronary
artery that we're dealing with.
157.1 -> The muscle cells over here
are going to get less oxygen.
161.37 -> So this guy-- let me draw
this cell right over here.
165.52 -> And I'm just drawing an
oversimplified diagram.
168.02 -> I'm not going to imply
that muscle cells really
170.36 -> look like that.
171.35 -> And actually, they
won't be-- well,
172.996 -> I won't go into
the details here.
174.37 -> But this guy's not going
to get not enough oxygen.
183.81 -> So you can imagine
that if we're really
186.56 -> zoomed in on the
surface of the heart,
188.48 -> we're looking at the heart
muscle tissue right here.
191.61 -> If whoever's heart this was,
if they started to go jogging
194.3 -> or whatever, and this
cell needed more oxygen,
198.14 -> probably wouldn't be able
to get that oxygen because
201.41 -> of the stenosis which
caused ischemia.
204.31 -> And because of that, it
doesn't have enough oxygen
206.68 -> so it won't be able to
help the heart pump.
208.669 -> Remember, this is just one of
the muscles in the heart that's
211.21 -> going to help it pump
the blood properly.
213.61 -> So it's going to lead
to heart failure.
218.077 -> And once again, the
word heart failure
219.66 -> sounds more dramatic
than maybe it really is.
222.8 -> It sounds like cardiac
arrest, where the heart stops.
225.25 -> But heart failure is not saying
that the heart is completely
227.33 -> failed.
228 -> It's just saying that the
heart is failing its ability
230.96 -> to kind of properly
do its function.
233.01 -> So when this guy goes
jogging, because he
235.04 -> has a restricted blood
supply, because the heart is
238.72 -> experiencing ischemia
downstream from this stenosis,
244.83 -> that's why there's
heart failure.
246.62 -> So not able to deliver.
248.39 -> Now this heart failure, which
is due to the ischemia which
252.07 -> is due to the stenosis, you
would call this heart failure
255.48 -> due to coronary artery disease.
258.264 -> Let me write it.
258.93 -> We talked about
that two videos ago.
264.94 -> Coronary artery disease.
267.28 -> Which is really just kind of
an impairing of the heart's
271.56 -> function because of
reduced blood supply,
274.5 -> because of a narrowing
in a blood vessel
277.12 -> restricts the blood
supply ischemia,
279.36 -> that is coronary artery disease.
281.41 -> And because of coronary
artery disease,
285.21 -> when this muscle
cell in the heart
286.73 -> really needs to pump hard--
maybe because someone's
288.95 -> going up a hill or
climbing stairs--
290.65 -> it's not able to do it because
it's not getting enough oxygen.
293.5 -> And that inability to
properly, for the heart,
296.53 -> not just the cell, but for the
whole heart, this is just one
299.207 -> of many cells that maybe won't
be able to pump properly,
301.54 -> for the entire heart to not do
its job, that is heart failure.
305.94 -> Now you've also probably
heard the term coronary heart
308.795 -> disease.
314.63 -> Or maybe just heart disease.
319.83 -> These three things are
all the same thing.
323.6 -> These are all the same.
325.05 -> They all imply some type
of narrowing or stenosis
328.64 -> of arteries that leads to
ischemia, reduced blood flow,
332.97 -> so that the heart can't function
as well as it otherwise could.
337.29 -> Now the last thing
I want to focus on,
338.97 -> and I talked a little bit
about it in the last video,
341.32 -> is the idea of an
infarct or an infarction.
344.39 -> These are kind of
funny words to say.
347.48 -> I'll write it over here.
348.75 -> So infarct or infarction.
353.33 -> So in the example I've drawn
so far, this cell, for example,
357.85 -> maybe does not
get enough oxygen,
359.68 -> especially once the
person is going upstairs
361.69 -> and all of that, to properly
contract and help the heart
366.2 -> actually pump.
367.39 -> But it's not dead.
368.81 -> It's still getting
some base level oxygen.
371.28 -> Less because of the
stenosis and the ischemia,
374.34 -> but it still gets some oxygen.
376.14 -> And we saw in the video
on myocardial infarction
379.03 -> or the video on heart
attacks that sometimes one
381.76 -> of these plaques might become
unstable and they break off
385.58 -> and then you have
a complete blocking
389.6 -> of a vessel, a complete blocking
of an artery right here.
393.699 -> And we saw in the
last video, we call
395.24 -> this blocking what's
called an embolism.
397.33 -> And an embolism is the
general term for something
401.21 -> that floated around and then
eventually blocks a vessel.
404.39 -> And if it was due to kind of
a released plaque that also
408.19 -> had clotting factors around
it after it got released,
410.53 -> then we would call
this a thromboembolism.
414.86 -> This would reduce the
blood flow so much,
420.011 -> maybe a little bit might
be able to leak around,
422.01 -> but it reduces it so much that
the cells downstream from this
425.6 -> actually die.
427.36 -> So you actually have
the cell right over here
429.25 -> and this cell will die.
431.36 -> It might get very little
blood or no blood at all,
434.1 -> so it's not getting enough
oxygen to actually survive.
437.99 -> And when you have dead tissue
that's due to a loss of oxygen,
443.97 -> this is an infarct, dead
tissue due to a loss of oxygen.
447.55 -> The process of it becoming dead
tissue due a loss of oxygen
451.97 -> is an infarction.
454.28 -> And this infarction, this
dead tissue due to loss
457.2 -> of oxygen, in the myocardium, in
the muscle tissue of the heart.
461.915 -> So now all of a sudden
you have muscle tissue
463.79 -> in the heart that's
beginning to die.
465.61 -> This is a heart attack.
466.73 -> This is a myocardial infarction.
469.51 -> So hopefully that clarifies
things a little bit.
Source: https://www.youtube.com/watch?v=3858MaULDdI