Basics of heart disease, heart attacks, heart failure, angina, cardiac arrest. Special thanks to Edward J Perper, MD for help in clarifying certain aspects of this video. Licensed under CC-BY-SA.Created bySal Khan.
I think most of us know what the heart does in our body. It pumps the blood and in particular it takes in the blood from the rest of the body. That is blue over here in this diagram, because that blood does not have carried oxygen And it pumps that blood to the lungs where the blood gets oxygenated. And then it comes back from the lungs, depicted as red blood, now that it has oxygen in it. And then that oxygenated blood is pumped to the rest of the body. And I think also, most of us have the general idea that when people talk about heart disease or heart attacks, which we learn, are two different things, related but different things, that has something to do with the clogging of arteries. so when I was a kid and I first learnt about the clogging of arteries. and I knew enough that the heart is all about pumping blood to the body. I assumed the artery that people were talking about these big arteries that were coming away from the heart to the rest of the body that somehow these things got clogged up. so let me draw that, different colour you can see so this was my ....this is what I thought people were talking about when they were saying clogging of the arteries and maybe when they got clogged enough, the stopped blood flow to the rest of the body somehow and that would actually kill the person. I want to make it very clear right now. Those are not the arteries that people are talking about getting clogged, when people talk about heart disease or heart attacks. The arteries that they are talking about are the arteries that actually provide blood to the heart. Remember the heart itself is a muscle. It itself needs oxygen. So you have these arteries right over here, the red tubes. Those are arteries. and then the blue ones are veins. They're taking the de-oxygenated blood away from the tissue of the heart. And these are called coronary arteries. And this one over here at least from the point of view of me or you looks like it's on the right. Or from the point of view of the person whose heart it is, it's on the left. This right over here is called the left coronary artery or LCA. And this right over here in red is called the right coronary arteries or the RCA. And so when people talk about arteries getting blocked or getting clogged, they're talking about the coronary arteries. They're talking about the things that supply blood to the heart. So let's zoom in on one of them....Maybe we can zoom in right over here, that part of the artery. That's the tube....clear where I am zooming in. I am zooming in right over here. So over time, I am not going into the details how this happened. It is subject for another video. You can have these plaques build up along the walls of the artery. So over time if a person doesn't have the right diet, or maybe they just have a predisposition to it, you can have these things called plaques form on the walls of the arteries. And the plaques, the material inside of them are lipids, so things like fat, cholesterol and also dead white blood cells, which is this kind of messy substance right over here. This is what we call a plaque. And the formation of these plaques that obstruct the actual blood vessel, that actually obstruct the artery. We call it.....make it clear you see that. This is kind of tube over here. Let me draw the blood So this formation of these plaques we call atherosclerosis. So you can imagine if you have these things build up, it's narrowing the actual vessel that's supplying blood downstream from that obstruction. So it would be destructing the blood flow downstream right over there. In that general process we talk about the restriction of blood flow, that is ischemia that's happening. So ischemia is deprivation of blood flow and oxygen downstream from this right over there. That's what we call coronary artery disease, or heart disease. So this causes coronary artery disease, which is sometimes called heart disease. Coronary heart disease would be redundant, because coronary is already referring to the heart. This is also sometimes called heart disease. And so you can imagine if downstream the muscle tissue is not getting all the oxygen it needs, especially maybe when this person, whoever's heart this is, when they are exerting themselves, they need more oxygen. The heart needs to pump a little harder. If downstream the cells are not getting all of the oxygen they need, you can imagine that the heart maybe not able to provide all of the functions, whoever's heart this is, that they needed to do. And when that happens that's called heart failure. So heart disease is one of the causes of heart failure. Now I want to be clear, heart failure does not mean that the heart is stopping. That the heart is stopped and the person is dead, it literally just means that the heart is failing to do what it should be doing. It's failing to provide the needs of that person. So it's not pumping hard enough or well enough to provide adequate function for that person. The other symptom that actually might occur when someone has coronary heart disease, where they have obstruction or this ischemia or this deprivation of oxygen downstream from this obstruction, is that they might experience this kind of strangling chest pain That's called angina pectoris or sometimes angina. Very few people say the pectoris part. Sometimes you hear people say oh angina. Angina pectoris, which is really chest pain, angina literally comes from meaning this kind of strangling feeling, and pectoris is in the chest. This is strangling feeling in the chest. This is a symptom of heart disease. Now this is already not a situation you want to get into because already your body is not able to function as well as it maybe could be, as maybe it could. Sometimes as I might describe here is a plaque. Some plaques are actually unstable. These plaques just grow and grow and grow. It makes probably heart disease worse and worse, heart failure worse, and angina pectoris worse. These plaques are unstable. It can actually rupture. You can imagine all these blood flows, as plaque grows, the blood flows become a little turbulent around these plaques. It has to go really fast through this narrow section. It comes out turbulent on the inside and creates these friction and all the rest. At some point, you can imagine this plaque is unstable. It could actually rupture. Let me draw ruptured plaque over here....let me draw the same one....I am gonna draw the ruptured. Now this plaque has rupture. It got so big. Maybe the turbulent blood flow helped stimulate this and whatever else. For whatever reason, it ruptures. When it ruptures, now it sudden i am doing a simplification of the process right over here. Now the content of this plaque: the lipid, the cholesterol, the fat, the dead white blood cell. Now it sudden is exposed to the blood flow. in particular to the clotting factor in the blood. This is highly thrombogenic material. Thrombogenic, very fancy word. That just means, that tends to cause blood clot. Thrombosis is a blood clot. What happened is, as soon as this type of things happened, it can literally happen in seconds or in minutes. All the sudden you could have these clotting factors form a clot right over here right at the actual plaque. As this happens, it starts to really really really obstruct the blood vessel. Sometimes it can even completely obstruct the blood vessel. When it happens, you are significantly depleting the blood flow going downstream from there. You might even be shutting it off. When you do that, the cells downstream will no longer get oxygen. They will die. This right over here, is called an infarction. an infarct is actually a dead heart tissue. You can imagine when heart tissue begins to die, this is even worse than what we were describing with coronary heart disease. Not only coronary heart disease just is not getting enough oxygen, now they are actually dead. They are turning into dead tissue. This process of completely or almost completely depriving cells of oxygen so that they die, this is a heart attack. Let me completely obstruct this artery to make the point clear. this right over here is a heart attack. This is the primary cause of heart attack. It's less likely but sometimes a plaque could also go downstream, kind of form a thromboembolism. It would be this thrombogenic material, the clots around it. It would actually go and block the artery further downstream and be embolism. That can also block the artery and cause tissue to die. But the main cause is this intense clotting that can occur pretty quickly and completely obstruct the artery. There is one last word i want to touch sometimes mixed in with all the other words, that is cardiac arrest. That's because sometimes we use them in the same context. one thing can lead to another. Heart attack is not cardiac arrest. Cardiac arrest is the actual dying of the heart. What I just described in a heart attack, people can have a heart attack. They will have some part of their muscle tissue die. Some part infarct, that's what they called myocardial infarction. Myocardial means the tissue of heart or the muscle of the heart that's dying. Sometimes it is called myocardial infarction. That is not cardiac arrest. Cause you can have some of your heart tissue die and you can survive. Your heart would be impaired. But you will continue to live. Cardiac arrest is literally your heart stopping. This would obviously cause someone to die. If you have a bad enough heart attack, if you have enough of the tissue get starved of oxygen so that it dies, infarction occurs. Then it could lead to cardiac arrest. It always won't lead to cardiac arrest. Frankly, heart attack is not the only thing that can cause cardiac arrest. I also want to once again differentiate cardiac arrest from heart failure, because they sound the same, sound like heart is failing. Cardiac arrest is heart stopping. Heart failure is essentially just saying that heart can not provide all of the needs for the body.