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As someone who's married to a doctor. In the medical field, it's pretty important to have a precise

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understanding of what the words mean, just so you can understand what people

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are talking about. If either you are a health care professional, or if one is talking to you

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as my wife does... well, sometimes does, when she comes home from work.

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So let's get a little more precise with the words we've been talking about, especially with

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heart disease and heart failure and all of the rest. So let's say this is an artery

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and the blood is flowing in that direction... and let's say this right here is an artery.

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Now, let me draw a plaque there. and we've been studying plaque since the video on heart attacks.

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So let's say this is a clump of white blood cells and lipid materials and all the rest

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Now, a word that you might hear in a medical context is "stenosis", and the word

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just refers to the narrowing, usually of a blood vessel. So, this right here, this blood vessel has been narrowed.

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It can also refer to the narrowing of any type of tubular structure, so if you have

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any type of pipe in a biological system, you can use stenosis there, but usually they're

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talking about a blood vessel. In this example here, it's an artery.

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Now, once the blood vessel is narrowed, that restricts the blood supply

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so you aren't able to get as much blood through it, so the blood supply

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is restricted. This restriction of blood supply that usually leads to some loss of function

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is called 'ischemia', another fancy word, that literally just means 'restricted blood supply'.

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Now if you have stenosis in one of your blood vessels, and it leads to ischemia

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then the muscles, and let's just say this a coronary artery here...

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the muscle cells over here are going to get less oxygen.

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So this muscle cell over here is not going to get enough oxygen -- and this is an oversimplified diagram

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And, this is not what an actual muscle cell looks like. But I don't want to get into detail here...

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But, this guy is not going to get enough oxygen. So, you can imagine that if we're really zoomed in on the surface of the heart

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and we're looking at the cardiac muscle tissue, if this person with this heart needed to go jogging

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and this cardiac muscle cell needed oxygen, they probably wouldn't be able to get the needed oxygen

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because of the stenosis which caused ischemia.

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And because of that, this cell won't be able to help the heart pump properly

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So this is going to lead to heart failure, and once again the word heart failure

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sounds more dramatic than it really is. It sounds like the heart stops (cardiac arrest)

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but it's really just saying that the heart is failing to PROPERLY do it's function -- not entirely shutting down.

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So when this guy is jogging, because he has restricted blood supply

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because the heart is experiencing ischemia downstream from

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this stenosis, that's why there's heart failure -- so not able to deliver

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Now, this heart failure which is due to the ischemia and the stenosis

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you would call this heart failure due to 'Coronary Artery Disease'

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which is really just kind of an impairing of the heart's function

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because of reduced blood supply, because of narrowing of the blood vessels

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that is Coronary Artery Disease, and because of this disease

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when this muscle cell in the heart really needs to pump hard

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maybe because someone's going up a hill or climbing stairs

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it won't be able to do it because it's not getting enough oxygen.

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Now, that inability to properly pump -- not just the cell, but the whole heart -- that is heart failure.

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Now you've probably the heard the term 'Coronary Heart Disease'

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or maybe just 'Heart Disease'... these three things are all the SAME thing.

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They all imply some sort of narrowing, or stenosis, of arteries that leads

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to ischemia, reduced blood flow, so that the heart can't function

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as well as it otherwise could. Now the last thing I want to focus on

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and I talked a little bit in the last video, is the idea of an infarct or infarction.

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These are kind of... funny words to say, so I'll right it over here

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So, an infarct or infarction... now, in the example I've drawn so far

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this cell maybe doesn't get enough oxygen, especially when the person is going up stairs and all of that,

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to properly contract the heart and pump blood. But this cell is not dead.

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It's still getting some base level oxygen -- less because of the stenosis and ischemia

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but it still gets some oxygen. Now we saw on the video on myocardial infarctions

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or heart attacks that sometimes, one of these plaques might become

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unstable and they break off and then you have a complete blocking

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of a vessel, and we called this -- if it's an embolus...

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and remember that an embolus is something that is just floating around

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and eventually blocks a vessel, and if it was a due to a ruptured

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plaque that also had clotting factors around it when it was released,

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then we would call this a thromboembolism.

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And this would reduce the blood flow so much, that the cells downstream

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from this location actually die

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because it's not even getting enough blood, not enough oxygen, to survive

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and when you have dead tissue that's due to a loss of oxygen, this is an infarct.

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The process of it becoming dead tissue due to a loss of oxygen

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is an infarction. When this infarction occurs in the muscle tissue of the heart, this is a heart attack

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This is a myocardial infarction... so hopefully that clarifies things a little bit.