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Stenosis, ischemia and heart failure

Video transcript
As someone who's married to a doctor, in the medical field, I think it's pretty important to have a precise understanding of what the words mean, just so that you can understand what people are talking about if either you are a health care professional or if some health care professional is talking to you, as my wife does when, well, sometimes does, when she comes home from work. So let's get a little bit more precise with some of the words we've been talking about, especially relative to heart disease and heart failure and all of the rest. So let's say this is an artery. The blood is flowing in that direction. I'll show the artery branching off. It thins as it goes farther and farther along. So this right here is an artery. And let me draw a plaque in that artery. And we've been studying these plaques in arteries since the video on heart attacks. So let's say that this is a bunch of white blood cells and lipid material. So it's cholesterol and fats and all the rest. Now a word that you might hear in kind of a medical context is stenosis. And the word "stenosis" just refers to the narrowing, usually of a blood vessel. So this right here, this blood vessel has been narrowed. So this right over here is stenosis. It's been narrowed by this plaque. It can also refer to the narrowing of kind of any type of tubular structure. So if you have any type of kind of pipe in a biological system and it gets narrow, they might refer to stenosis there. But usually they're talking about a blood vessel. In this example that I've drawn here it's an artery. So the stenosis is just the narrowing. 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. So restricted blood supply. Put the I there. Restricted blood supply. This restriction of a blood supply that usually leads to some type of loss of function, that's called-- so this restricted blood supply-- this is called ischemia. Another fancy word, but it literally just means restricted blood supply. Ischemia. Now if you have stenosis in one of your blood vessels, in one of your arteries, and it restricts your blood supply. So it leads to ischemia. Let's say let me draw a muscle cell farther over here. Let's say this is a coronary artery that we're dealing with. The muscle cells over here are going to get less oxygen. So this guy-- let me draw this cell right over here. And I'm just drawing an oversimplified diagram. I'm not going to imply that muscle cells really look like that. And actually, they won't be-- well, I won't go into the details here. But this guy's not going to get not enough oxygen. So you can imagine that if we're really zoomed in on the surface of the heart, we're looking at the heart muscle tissue right here. If whoever's heart this was, if they started to go jogging or whatever, and this cell needed more oxygen, probably wouldn't be able to get that oxygen because of the stenosis which caused ischemia. And because of that, it doesn't have enough oxygen so it won't be able to help the heart pump. Remember, this is just one of the muscles in the heart that's going to help it pump the blood properly. So it's going to lead to heart failure. And once again, the word heart failure sounds more dramatic than maybe it really is. It sounds like cardiac arrest, where the heart stops. But heart failure is not saying that the heart is completely failed. It's just saying that the heart is failing its ability to kind of properly do its function. So when this guy goes jogging, because he has a 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 which is due to the stenosis, you would call this heart failure due to coronary artery disease. Let me write it. We talked about that two videos ago. Coronary artery disease. Which is really just kind of an impairing of the heart's function because of reduced blood supply, because of a narrowing in a blood vessel restricts the blood supply ischemia, that is coronary artery disease. And because of coronary artery 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's not able to do it because it's not getting enough oxygen. And that inability to properly, for the heart, not just the cell, but for the whole heart, this is just one of many cells that maybe won't be able to pump properly, for the entire heart to not do its job, that is heart failure. Now you've also probably heard the term coronary heart disease. Or maybe just heart disease. These three things are all the same thing. These are all the same. They all imply some type 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 about it in the last video, is the idea of an infarct or an infarction. These are kind of funny words to say. I'll write it over here. So infarct or infarction. So in the example I've drawn so far, this cell, for example, maybe does not get enough oxygen, especially once the person is going upstairs and all of that, to properly contract and help the heart actually pump. But it's not dead. It's still getting some base level oxygen. Less because of the stenosis and the ischemia, but it still gets some oxygen. And we saw in the video on myocardial infarction or the video on 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, a complete blocking of an artery right here. And we saw in the last video, we call this blocking what's called an embolism. And an embolism is the general term for something that floated around and then eventually blocks a vessel. And if it was due to kind of a released plaque that also had clotting factors around it after it got released, then we would call this a thromboembolism. This would reduce the blood flow so much, maybe a little bit might be able to leak around, but it reduces it so much that the cells downstream from this actually die. So you actually have the cell right over here and this cell will die. It might get very little blood or no blood at all, so it's not getting enough oxygen to actually survive. And when you have dead tissue that's due to a loss of oxygen, this is an infarct, dead tissue due to a loss of oxygen. The process of it becoming dead tissue due a loss of oxygen is an infarction. And this infarction, this dead tissue due to loss of oxygen, in the myocardium, in the muscle tissue of the heart. So now all of a sudden you have muscle tissue in the heart that's beginning to die. This is a heart attack. This is a myocardial infarction. So hopefully that clarifies things a little bit.