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All right. Let's talk about hypertension. And the first thing we have to do is understand the two main categories, or types, of hypertension that are out there. So there are two types, primary-- and this is actually also called essential hypertension. You might hear that word, essential. And secondary. And I'll write that as a two. And so the way that this is divided up is that primary hypertension is caused by something indirect. OK, so what does that mean exactly? So I'll give you some examples of what the indirect cause could be. It could be something like smoking, or it could be that someone has obesity or is obese. Or it could be that they have hyperlipidemia, meaning that they have lots of fats floating around in the blood. Or let's say they have diabetes. That would be another cause, or indirect cause, of hypertension. And these are all risk factors, right? That's another way of thinking about these things. These are general risk factors for having hypertension. And the other category would be something direct. And once I write this down, you'll start seeing the difference. This would be something like kidney disease. So let's say that I have a problem with my kidneys. And they, for some reason-- these are my kidneys-- they are holding on to far too much fluid than they should. And that's because they're diseased. And so they're holding onto too much fluid. And they're causing my volume of blood to go up. There causing the volume to go up, and the stroke volume is going up as well. And if the stroke volume goes up, you know that stroke volume is going to cause a higher blood pressure, because they're directly related to each other-- very direct. That would be one example. Another example could be-- let's say I have what's called an "aortic coarctation." So this is a very specific problem. This would be-- if I have my-- let's say the heart is here. And I have the aorta coming off here. Normally, it should be nice and open, the way I've drawn it. But if you have a coarctation, then you might have a pinching in of the vessel. So it would start looking like this. It would look like that, like a pinch. And if you have a pinching in right there, then you have increased resistance. And if you have increased resistance, you know, again, resistance is going to relate back to pressure. So if you have more resistance, you have higher pressure. So these are direct causes of hypertension, which is slightly different than the indirect causes I wrote above-- the smoking, obesity-- because there's no clear direct mechanism in any of those things. They're just more general risk factors. So this is how we kind of divvy up the two groups. And we say, OK, if you have one or the other, then you're in the primary or secondary group. So let's figure out, of the two, which is more prevalent. And this basically means, which is going to affect more people at any point in time. So if I was to poll all people with hypertension-- ask them, hey, what group are you in, primary or secondary-- most people would say primary, because most of these people are going to be smokers or obese or diabetics or people that have hyperlipidemia, some of these risk factors that we just laid out. In fact over, 90% of the people have primary hypertension. And only a few people, I would say less than 10%, are going to say, nope, I'm actually in the secondary group. I have a very specific reason for having hypertension. So this is actually a very easy way of figuring out if people are having hypertension from an indirect cause or a direct cause. All right. So now, let's assume that you follow one person over time, one individual. And that person used to have normal blood pressure. Let's say this is blood pressure over here. And I'm going to write it out as Mean Arterial Pressure, MAP. Mean Arterial Pressure. And we want to maintain a Mean Arterial Pressure, a MAP, of a certain number. So this would be like a normal blood pressure range, right? Something below this dashed line. So this is normal. But of course, many people have something higher than normal. They, over time, might develop higher blood pressure. So maybe they start out here and here in the normal range. And then they start having high blood pressure. And it kind of goes up and down, and up and then down and stops there. So in this person-- I'm going to connect the dots-- they, if you asked them, would not have any symptoms for most of the time. They would actually say, you know, I feel fine. I don't have any symptoms at all. In fact, up until this point in time, they would say they have no symptoms. And the vast majority of people are actually in this group. So most people with hypertension, if you ask them if they have symptoms from it, they would say no, they don't have any symptoms. But at some point, they can develop symptoms. Not everybody, but you can develop symptoms. And when you do, it's usually quite significant. So you might have problems with your heart. Maybe your heart is having to work harder than it ever had to, and you're having some heart failure. Or you might have problems with your large vessels or medium vessels. And primarily, these are the arteries, because the arteries are the vessels that are seeing those high pressures. And those arteries might be getting very stiff. Or you might have problems with tiny vessels. These are the little arteries, the smallest ones, or the arterioles. And remember, the smallest arteries and arterioles, they're not sitting there naked in your body. They're usually within an organ, right? So they're usually within the kidney, or they could be within the eye. So I'll just draw these two. So they're usually within some other organ. And if you have problems with the smallest arterioles-- let's say they're breaking-- then really, what you're saying is you're going to have kidney problems or eye problems. So these are the kind of problems you can get. And because most people are having no symptoms-- most people are over here-- you really want to catch them before they cross over from no symptoms to having symptoms. And you want to take care of the blood pressure problem so that they never develop any symptoms. That's the goal. Now, unfortunately, some people develop what's called "malignant hypertension." And I'm going to write out for you what malignant hypertension means. It's a few things. And we can actually even draw it on our figure. Maybe I'll do that. So you have people with malignant hypertension that have a rapid rise in their blood pressure. And it causes damage to the heart and vessels. And finally, the range that we're talking about, it's a rapid rise to a really high blood pressure. Sometimes we think of these pressures being around 240 over 120-- really high blood pressures. So on our graph, this could be the person that-- unlike the person in white, this person maybe had a very quick rise in pressure. And then it got very high, maybe got up to 240 over 120. And so this would be the third point. The rapid rise is the first point. And the fact that they're having symptoms is point number two. So you can see now how someone with malignant hypertension could look on this sort of a graph.