Heart Disease and Stroke
Stenosis, ischemia and heart failure Clarifying a bunch of medical terms around heart disease
Stenosis, ischemia and heart failure
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- As someone who's married to a doctor. In the medical field, it's pretty important to have a precise
- understanding of what the words mean, just so you can understand what people
- are talking about. If either you are a health care professional, or if one is talking to you
- as my wife does... well, sometimes does, when she comes home from work.
- So let's get a little more precise with the words we've been talking about, especially with
- heart disease and heart failure and all of the rest. So let's say this is an artery
- and the blood is flowing in that direction... and let's say this right here is an artery.
- Now, let me draw a plaque there. and we've been studying plaque since the video on heart attacks.
- So let's say this is a clump of white blood cells and lipid materials and all the rest
- Now, a word that you might hear in a medical context is "stenosis", and the word
- just refers to the narrowing, usually of a blood vessel. So, this right here, this blood vessel has been narrowed.
- It can also refer to the narrowing of any type of tubular structure, so if you have
- any type of pipe in a biological system, you can use stenosis there, but usually they're
- talking about a blood vessel. In this example here, it's an artery.
- Now, once the blood vessel is narrowed, that restricts the blood supply
- so you aren't able to get as much blood through it, so the blood supply
- is restricted. This restriction of blood supply that usually leads to some loss of function
- is called 'ischemia', another fancy word, that literally just means 'restricted blood supply'.
- Now if you have stenosis in one of your blood vessels, and it leads to ischemia
- then the muscles, and let's just say this a coronary artery here...
- the muscle cells over here are going to get less oxygen.
- So this muscle cell over here is not going to get enough oxygen -- and this is an oversimplified diagram
- And, this is not what an actual muscle cell looks like. But I don't want to get into detail here...
- 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
- and we're looking at the cardiac muscle tissue, if this person with this heart needed to go jogging
- and this cardiac muscle cell needed oxygen, they probably wouldn't be able to get the needed oxygen
- because of the stenosis which caused ischemia.
- And because of that, this cell won't be able to help the heart pump properly
- So this is going to lead to heart failure, and once again the word heart failure
- sounds more dramatic than it really is. It sounds like the heart stops (cardiac arrest)
- but it's really just saying that the heart is failing to PROPERLY do it's function -- not entirely shutting down.
- So when this guy is jogging, because he has restricted blood supply
- because the heart is experiencing ischemia downstream from
- this stenosis, that's why there's heart failure -- so not able to deliver
- Now, this heart failure which is due to the ischemia and the stenosis
- you would call this heart failure due to 'Coronary Artery Disease'
- which is really just kind of an impairing of the heart's function
- because of reduced blood supply, because of narrowing of the blood vessels
- that is Coronary Artery Disease, and because of this disease
- when this muscle cell in the heart really needs to pump hard
- maybe because someone's going up a hill or climbing stairs
- it won't be able to do it because it's not getting enough oxygen.
- Now, that inability to properly pump -- not just the cell, but the whole heart -- that is heart failure.
- Now you've probably the heard the term 'Coronary Heart Disease'
- or maybe just 'Heart Disease'... these three things are all the SAME thing.
- They all imply some sort of narrowing, or stenosis, of arteries that leads
- to ischemia, reduced blood flow, so that the heart can't function
- as well as it otherwise could. Now the last thing I want to focus on
- and I talked a little bit in the last video, is the idea of an infarct or infarction.
- These are kind of... funny words to say, so I'll right it over here
- So, an infarct or infarction... now, in the example I've drawn so far
- this cell maybe doesn't get enough oxygen, especially when the person is going up stairs and all of that,
- to properly contract the heart and pump blood. But this cell is not dead.
- It's still getting some base level oxygen -- less because of the stenosis and ischemia
- but it still gets some oxygen. Now we saw on the video on myocardial infarctions
- or heart attacks that sometimes, one of these plaques might become
- unstable and they break off and then you have a complete blocking
- of a vessel, and we called this -- if it's an embolus...
- and remember that an embolus is something that is just floating around
- and eventually blocks a vessel, and if it was a due to a ruptured
- plaque that also had clotting factors around it when it was released,
- then we would call this a thromboembolism.
- And this would reduce the blood flow so much, that the cells downstream
- from this location actually die
- because it's not even getting enough blood, not enough oxygen, to survive
- and when you have dead tissue that's due to a loss of oxygen, this is an infarct.
- The process of it becoming dead tissue due to a loss of oxygen
- is an infarction. When this infarction occurs in the muscle tissue of the heart, this is a heart attack
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