What is coronary artery disease? | Circulatory System and Disease | NCLEX-RN | Khan Academy



so you got your heart right and so your heart is sitting in your chest and it's this muscular pump that will pump blood throughout your body so it needs to pump blood to to all the places in your body and and it actually does a lot of work it pumps about a hundred thousand times a day I'm not making that number up it actually pumps if you if you take the average heart rate which is about 72 beats a minute and then you multiply that through for a day that ends up being about a hundred and three thousand beats per day right so it's this really hard working muscle it's really hard working organ and what do hard-working muscles need well just think about the last time you went on a run or climbed a fence or or did a backflip or whatever it is that you do to get your muscles working they need a lot of oxygen right what did you feel after you after you did all this exercise I mean you were probably gasping for air you're panting you're just at least you were breathing heavier right and the reason for that is because you you your muscles you've used them you've exhausted a little bit and now you have to pay back oxygen right if they you have to give them oxygen your heart is really no different you might be thinking well the heart is getting access to all of the blood that it pumps out right so it doesn't it just get like basically an unlimited supply of oxygen from that from that blood well it doesn't actually so let me actually draw this for you in cross-section so we're going to take a section through here and and we'll blow it up right here and and you can kind of see right here that the walls are pretty thick and so the oxygen in the blood flowing inside the heart it can't actually reach all the way across the the thick heart muscle wall it might be able to get to a little bit of the inner section of the wall but it can't diffuse across the whole heart muscle wall because it's just too thick so we have a solution for that actually and then this solution is the coronary arteries and the coronary arteries run on the outside of the heart so here's a heart you can see this person's right coronary artery and you can see this person's left coronary artery right actually this is this is actually the left anterior descending artery which is a branch of the left coronary artery so so again these coronary arteries are the solution right where they bring copious amounts of blood to the heart muscle and they they feed it enough blood to do all the work that the heart needs to do but sometimes they can get diseased and so coronary artery disease is one of the problems that can go wrong with with the coronary coronary vessels so you may have heard the term clogged arteries to describe coronary artery disease and why they're called clogged arteries is because there's this build-up of fatty substances that's almost like a plumbing being clogged so let's actually draw this out so so here is here's a close-up of the coronary vessel right so we have one wall there and the other wall here so so here's your blood and and here are some components of your blood so you've got you got your red blood cells and here's some cholesterol and here's some white blood cells and and when the cholesterol is sort of flowing through your your blood and it comes across a bit of damaged blood vessel wall the cholesterol thinks hey that looks like a pretty cool spot to hang out and so the cholesterol actually will start to deposit inside the walls inside the damaged walls of your blood vessels and the white blood cells don't really like this so the white blood cells try to follow in after the cholesterol to get rid of them to get them out of the wall and that kicks off this big inflammatory process called atherosclerosis and that just means hardening of the blood vessel because this whole process over time makes that blood vessel wall become hard and stiff and unfortunately during the process a lot of the white blood cells die so the cholesterol can just keep depositing in there and the cholesterol and the white blood cells sort of create this fatty bulge called a plaque and over time the plaque will start to bulge into the vessel why is that a problem well I mean blood needs to get through right if you've got this big bulge in the way how is blood going to get through so for the first little while I mean blood can get through and you won't have any problems but over time and I mean this this plaque takes decades for it to build up to a clinically significant level and that means when you start to get so overtime it'll just continue to grow and then you'll start running into some problems so again just to be perfectly clear coronary artery disease is when you start to get buildup of this plaque this fatty substance within the arteries of your of your heart let me just make some room here and why it's bad why coronary artery disease is bad is because downstream later in your life it can lead to some other heart diseases so we'll just we'll just briefly describe the main ones and we'll start with one you may have heard about before we'll start with stable angina so let's look at this bit of muscle down here that the arteries sending blood to well and let's put our plaque here let's say our plaque is here upstream when you're at rest when your heart's not doing too much work enough blood can get past that plaque and and get down and feed that muscle okay so that muscle is you know happy it's it's it's getting enough oxygen from the blood that's getting to it and you know it's not feeling any adverse effects it's totally happy right but what happens when you start to you know maybe you're you're going to miss your bus you need to run for your bus or you really want to impress that girl so you start taking dance classes when you when you ask your heart to do more work you know your heart rates going to go up your heart's going to beat a bit faster right and then all of a sudden not enough blood is going to be able to get past that plaque and feed that muscle right and so that piece of muscle becomes hypoxic when that muscle down there it gets hypoxic when it doesn't have enough oxygen to carry out its function you start to actually get a symptom you start to get a symptom called angina pectoris what angina pectoris refers to let's actually just look at the two words so you got angina right and angina is from the Greek word to strangle right and I know it sounds weird but people describe the the feeling of angina as sort of a tight strangling feeling in their chest pectoris refers to chest so angina pectoris is this tight strangling feeling in your chest that is brought on when your heart muscle doesn't have enough oxygen this is reproducible this is reproducible so if you sort of lower your activity level if you stop that amazing dance move I'm sure you're doing or if you stop running for the bus and you sort of take a breather then your heart you'll you're essentially asking your heart to do less work right and when your heart is doing less work it needs less oxygen and so all of a sudden that blood that's getting past that plaque is enough to supply that downstream bit of muscle again right so the the symptom of angina goes away the chest pain goes away because your your heart muscles getting all of the oxygen that it needs again okay so the reason that it's called stable angina remember this overarching condition is called stable angina and the reason it's called stable angina is because you can bring on you can predictably bring on the chest pain when you ask your heart muscle to do too much work exercise or exertion is going to cause it and rest is going to relieve it now things can get a little bit worse than that and when they get worse than that they can result in a suite of not sweet as in sweet I want that because you definitely don't want this but it refers to a set of conditions diseases that you can get called acute coronary syndrome and acute coronary syndromes they can be further subdivided into something called unstable angina let's make some more room and so you can imagine already because you know it's stable angina is you can kind of imagine what unstable angina is but you got unstable angina and then you have your heart attacks right so unstable angina just to just to be clear again stable angina not a heart attack unstable angina not a heart attack heart attack is a heart attack go figure so let's look at unstable angina first before we look at heart attacks unstable angina is remember that plaque we talked about let's go back to our nice little blood vessel here well it's not nice anymore it's got a huge honkin fatty plaque in it but that's alright so here's our blood vessel right here's our plaque now sometimes because of whether it's hypertension putting you know sheer stress on this plaque or web it's spontaneous this can happen spontaneously you know there's a couple other reasons right but those are those are probably the two major reasons the plot can rupture right and when I say rupture I mean I mean that this covering of the plaque on the inside the blood vessel can sort of burst right and when it bursts it exposes all the plaque material all that fatty gross sort of necrotic necrotic means a dead cells by the way because the cells in here of some of them are dead at this point it exposes them to the blood right and and plaque material is really thrombogenic what does thrombogenic mean thermogenic means it causes blood clots to form on it and let me just redraw this it's a little messy so when the blood sees that plaque material it's going to go crazy it's you got your platelets in your blood and you have your clotting factors in your blood and they're all going to grab on to that ruptured plaque material you're going to start to form a clot a blood clot on this ruptured plaque and you know from here one of two things can happen either this ruptured plaque can start to sort of flap back and forth right because it's it's ruptured on this end but it might still be attached on that end so what does this mean that means that you're gonna get sometimes your your blood vessels going to be completely occluded it's going to be completely blocked off and sometimes you're not going to have an occluded blood vessel because the plaque will be sort of stuck against the wall again but it's sort of just flapping around there and your blood vessel as blood goes by okay and so remember what we said earlier when you deprive downstream parts of the heart of blood you start to get that hypoxia happening and you start to get that chest pain that angina happening but remember now we have this plaque flapping around so at any point you could just lose blood supply to a downstream part of your heart temporarily and so in this condition unstable angina you can get chest pain at rest you don't actually have to exert yourself for for a chest pain to come on right and that's because it's just flapping around there it can happen at any point so that's why we call it unstable angina because it's not predictable and it can really just happen any time so the last thing now we need to talk about that's that's you know a part of acute coronary syndrome that's caused by coronary artery disease is heart attack right and so remember we said that this ruptured plaque is now exposed to the blood and remember the clotting factors have all started to clot onto it well blood cells can join in right join the party and one of two things can happen either the clot also called a thrombus by the way a clot is also called a thrombus can get so big that it completely blocks off that blood vessel and that's that's also called thrombosis to completely block off a blood vessel by a clot is called thrombosis or or it can break off so this clot this thrombus can break off also called embolization so what a bit of a thrombus breaks off it's called embolization so it can embolize and and float downstream and block off a smaller blood vessel so this is it floating downstream and blocking off a smaller blood vessel right so when either of those two things happen that's when you end up with something called a heart attack right because now that's not going to resolve on its own you've completely cut off oxygen to a part of the heart and so the the heart muscle that that artery is supplying will die because it's it now doesn't have its supply of oxygen and you know if you actually get to a hospital and you get either medication or some type of surgical intervention before about 20 minutes then you can save that bit of heart if that blockage so either via complete thrombosis so blockage of a the artery or embolization and blockage of a downstream artery if that lasts for more than about 20 minutes then that heart muscle that bit of heart muscle will permanently die and that's what a heart attack is now one more thing I want to clarify so a heart attack is not the same as heart failure heart failure is when your heart can't pump enough blood to the needs of your body that's heart failure right so heart attack is different the heart attack is when a piece of your heart muscle actually dies because it itself isn't receiving enough oxygen okay that's that's the difference between heart failure and heart attack although they can actually cause each other to happen

30 comments

  1. i understood CAD in 5 minutes from this video. i didn't understand the explanation from my textbook, thank you so much.

  2. Here we did a study to describe characteristics of patients with recurrent acute coronary syndrome (ACS) admitted to a tertiary care hospital. https://goo.gl/D3S71Z We found, patients with recurrent ACS were more likely to have unstable angina than myocardial infarction. They were more likely to present directly to hospital, and to have stopped smoking. Hypertension and hyperlipidemia were commoner among them, highlighting the need for better secondary preventive measures

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