Understanding Left Coronary Artery Anatomy

Today we're going to start with the left coronary artery anatomy. I have this image looped on the left hand side. This is in a different view. We'll go through the views in a different video, but this one is just about what are all the vessels that could come off of the left coronary artery? What are their names? How do I know the differences between them? And then we'll talk about identifying them in different views. This right here is the aortic root. So you're going to have like the ascending and the root right here. right and your catheter kind of come up here and engages into the left coronary artery. So this is the left cusp, you have a right cusp and then you have a non-coronary cusp because no coronary should come off of that because your pulmonary artery is right here. So in the left cusp you should have the left coronary artery coming off of it, then the right cusp the right coronary artery coming off of it. So we're going to start with the LCA, LCA, left coronary artery, don't get that gut. get that confused with the LAD. So first is the left main. That's really the first branch, the trunk of the tree. Not everybody has a left main. Some people's are longer. Some people's are really short. And then you have the bifurcation come off right after that's a short left main. And some people just don't have one where the LAD has its own ostium, the CERC has its own ostium. So then there's no LAD or there's no left main there. everybody's a little different. But for normal anatomy, we'll say this patient has left main, and then you're going to have two main branches coming off of that trunk of the tree. Okay, one is going to be the LAD, and then one is going to be the circumflex. So a lot of when you're learning anatomy and imaging, the first step is really identifying which one is the LAD and which one is the circ, because then all these little branches will make sense if you identify the main branch correctly. So off of the LAD, you have two options. You have diagonals or you have septal perforators. So diagonals, there's usually between maybe one to four. Some patients just have one, some have four, some have three, some have two. Okay. And then septals, you should have way more septals. And then you do diagonals in a normal healthy patient. Okay. Diagonals are bigger, but there's fewer of them. And then septals are smaller and there's more of them. Here is diagonal one and diagonal two and then we have a bunch of little septals and we don't we don't really name them because there's a lot more than what I drew here. The led is very long so you'll see we segment it so you'll see it says proximal led middle led and then distal led. So in order of blood flow what comes first is proximal and then the middle segment right is middle and then the end part of the perfusion is distal. If you look at textbooks, they'll really designate the transition from proximal to middle based on where the first diagonal comes off. So you see the first diagonal comes off here and then it transitions to what we would call mid-LAD. And then the distal LAD is where it starts to wrap around the apex of the heart. And then diagonals, again, we name in numbers. And the reason is if I read a report and it says, oh, patient got a stent to the diagonal. I want to know which one so then when I look on an angiogram I see they have three diagonals. Okay, which one had the stent? Same reason why you segment the LAD it's a very long vessel. If I say they had a proximal LAD stent, okay that's a lot more territory that was at risk versus a distal LAD stent right is really only just feeding the apex. So that location part is very important. So we're going to name it proc the first one to come off is diagonal one. and then the second one would be diagonal two and then they could have diagonal three diagonal four but you're just going to number them in order in which they show up in order of blood flow from proximal to distal. So then the circumflex is the other one okay circumflex feeds the lateral wall of the heart so you'll see the led is usually longer and it reaches and wraps around the apex and then the circ kind of cuts off and does a sharp like L turn or it will if you have a non-dominant circ. just kind of end here in what we call the AV groove, the atrioventricular groove. And that's because right here is both the coronary sinus right next to the CERC and the mitral valve is actually right here because this is your left ventricle and back here is your left atrium. Okay, so you see the CERC is a lot shorter than the LED, so we might not segment it depending on how large it is. Okay, you can just call this the CERC or if it's a large CERC, you could segment it into proximal and middle or distal CERC. you know that's very subjective but again the if it's a very long a very large dominant circ and then it's okay to kind of segment it but you really don't have to And then again the circ ends in the AV groove. So you see where it takes that turn that's the circ and then you see all these other branches going the opposite way will be named something else. Okay so what comes off the circumflex are om's obtuse marginals. Again you could have one, you could have two, you could have three. Okay so let's just say for right now we're going to call this om1, om2, om3 and then you have something else here that has little branches coming off of it that look like these stuff. because that's what they are. So then you're not going to call it an OM. The other rule of coronary arteries is like follows like, okay? And like looks like like. And what that means is if you notice both of these diagonals look the same, all of these septals look the same, but the septals don't look like the diagonals, okay? And the reason I wouldn't call this a septal is it follows the pattern of the diagonal before it, okay? So like follows like. Both of the diagonals go in the same direction. all of the septals go in the same direction, right? All of these OEMs go in the same direction and look the same. And then you have this one that kind of stands out from the rest. So it needs to be called something different. It's a different vessel. Okay. The one, not really anomaly, I would say, but something that not everybody has is you see, this is a real trifurcation. So you have this middle vessel. We call that the ramus intermedius, right? Intermedius for intermediate or the middle. It could be called a high obtuse marginal because it does follow the same pattern and it looks like the obtuse marginals and there's certain views we'll take to see if this is a real trifurcation then you can call it a ramus but let's say it came off like here okay that's not a real trifurcation and then we would call that a high obtuse marginal because it follows the pattern of the rest of these that come off the circ. It's definitely not a diagonal because it's all the way over here. It's not feeding where the diagonal feeds. And lastly, not everybody has this again, is the PDA, posterior descending artery. By definition, the PDA has these little things which look like these, right? So they're septal perforators, but it's not the LED because it's a completely different vessel. So this is the PDA, the posterior descending artery, and it is a branch off either. The RCA, which we'll talk about in a different video, or if it comes off the circumflex, okay, that is the PDA with septal perforators. You could have what we call a posterior lateral branch over here again, but that's for a different video. But this is kind of a classic left coronary artery look that is a dominant left coronary artery because you do see the PDA comes off of the circ. So this really, this left coronary artery feeds a large territory. of the myocardium of the heart. One tip I like to use to remember what comes off of what as far as the diagonals and the obtuse marginals. So let's type here LAD right and circumflex and then diagonal and obtuse marginals or the short thing that we call them are OMS. Okay, so let's just take a look at this wording really quick. And again, this might not work for everybody, but it is just a tip if you struggle with figuring out what branch comes off of what. Because remember, you identify really circ versus LAD first, and then you can kind of worry about these little things. So what comes off the LAD are diagonals K, D, and D. Haha, D&D if you play Dungeons & Dragons. And then what comes off the circumflex, I know this U isn't an O, right, but it looks more like an O than a D, are the obtuse marginals. Okay, the O-M's come off of the circumflex. And that's the end of this video. I hope this helps at least with basic coronary artery anatomy for the LCA. Stay tuned for the RCA and more.

How do I know the differences between them? And then we'll talk about identifying them in different views. This right here is the aortic root. So you're going to have like the ascending and the root right here.

right and your catheter kind of come up here and engages into the left coronary artery. So this is the left cusp, you have a right cusp and then you have a non-coronary cusp because no coronary should come off of that because your pulmonary artery is right here. So in the left cusp you should have the left coronary artery coming off of it, then the right cusp the right coronary artery coming off of it. So we're going to start with the LCA, LCA, left coronary artery, don't get that gut. get that confused with the LAD.

So first is the left main. That's really the first branch, the trunk of the tree. Not everybody has a left main. Some people's are longer. Some people's are really short.

And then you have the bifurcation come off right after that's a short left main. And some people just don't have one where the LAD has its own ostium, the CERC has its own ostium. So then there's no LAD or there's no left main there. everybody's a little different.

But for normal anatomy, we'll say this patient has left main, and then you're going to have two main branches coming off of that trunk of the tree. Okay, one is going to be the LAD, and then one is going to be the circumflex. So a lot of when you're learning anatomy and imaging, the first step is really identifying which one is the LAD and which one is the circ, because then all these little branches will make sense if you identify the main branch correctly. So off of the LAD, you have two options.

You have diagonals or you have septal perforators. So diagonals, there's usually between maybe one to four. Some patients just have one, some have four, some have three, some have two. Okay. And then septals, you should have way more septals.

And then you do diagonals in a normal healthy patient. Okay. Diagonals are bigger, but there's fewer of them. And then septals are smaller and there's more of them.

Here is diagonal one and diagonal two and then we have a bunch of little septals and we don't we don't really name them because there's a lot more than what I drew here. The led is very long so you'll see we segment it so you'll see it says proximal led middle led and then distal led. So in order of blood flow what comes first is proximal and then the middle segment right is middle and then the end part of the perfusion is distal.

If you look at textbooks, they'll really designate the transition from proximal to middle based on where the first diagonal comes off. So you see the first diagonal comes off here and then it transitions to what we would call mid-LAD. And then the distal LAD is where it starts to wrap around the apex of the heart. And then diagonals, again, we name in numbers. And the reason is if I read a report and it says, oh, patient got a stent to the diagonal.

I want to know which one so then when I look on an angiogram I see they have three diagonals. Okay, which one had the stent? Same reason why you segment the LAD it's a very long vessel. If I say they had a proximal LAD stent, okay that's a lot more territory that was at risk versus a distal LAD stent right is really only just feeding the apex.

So that location part is very important. So we're going to name it proc the first one to come off is diagonal one. and then the second one would be diagonal two and then they could have diagonal three diagonal four but you're just going to number them in order in which they show up in order of blood flow from proximal to distal. So then the circumflex is the other one okay circumflex feeds the lateral wall of the heart so you'll see the led is usually longer and it reaches and wraps around the apex and then the circ kind of cuts off and does a sharp like L turn or it will if you have a non-dominant circ.

just kind of end here in what we call the AV groove, the atrioventricular groove. And that's because right here is both the coronary sinus right next to the CERC and the mitral valve is actually right here because this is your left ventricle and back here is your left atrium. Okay, so you see the CERC is a lot shorter than the LED, so we might not segment it depending on how large it is. Okay, you can just call this the CERC or if it's a large CERC, you could segment it into proximal and middle or distal CERC.

you know that's very subjective but again the if it's a very long a very large dominant circ and then it's okay to kind of segment it but you really don't have to And then again the circ ends in the AV groove. So you see where it takes that turn that's the circ and then you see all these other branches going the opposite way will be named something else. Okay so what comes off the circumflex are om's obtuse marginals.

Again you could have one, you could have two, you could have three. Okay so let's just say for right now we're going to call this om1, om2, om3 and then you have something else here that has little branches coming off of it that look like these stuff. because that's what they are. So then you're not going to call it an OM. The other rule of coronary arteries is like follows like, okay?

And like looks like like. And what that means is if you notice both of these diagonals look the same, all of these septals look the same, but the septals don't look like the diagonals, okay? And the reason I wouldn't call this a septal is it follows the pattern of the diagonal before it, okay? So like follows like.

Both of the diagonals go in the same direction. all of the septals go in the same direction, right? All of these OEMs go in the same direction and look the same. And then you have this one that kind of stands out from the rest. So it needs to be called something different.

It's a different vessel. Okay. The one, not really anomaly, I would say, but something that not everybody has is you see, this is a real trifurcation. So you have this middle vessel.

We call that the ramus intermedius, right? Intermedius for intermediate or the middle. It could be called a high obtuse marginal because it does follow the same pattern and it looks like the obtuse marginals and there's certain views we'll take to see if this is a real trifurcation then you can call it a ramus but let's say it came off like here okay that's not a real trifurcation and then we would call that a high obtuse marginal because it follows the pattern of the rest of these that come off the circ. It's definitely not a diagonal because it's all the way over here. It's not feeding where the diagonal feeds.

And lastly, not everybody has this again, is the PDA, posterior descending artery. By definition, the PDA has these little things which look like these, right? So they're septal perforators, but it's not the LED because it's a completely different vessel. So this is the PDA, the posterior descending artery, and it is a branch off either.

The RCA, which we'll talk about in a different video, or if it comes off the circumflex, okay, that is the PDA with septal perforators. You could have what we call a posterior lateral branch over here again, but that's for a different video. But this is kind of a classic left coronary artery look that is a dominant left coronary artery because you do see the PDA comes off of the circ.

So this really, this left coronary artery feeds a large territory. of the myocardium of the heart. One tip I like to use to remember what comes off of what as far as the diagonals and the obtuse marginals.

So let's type here LAD right and circumflex and then diagonal and obtuse marginals or the short thing that we call them are OMS. Okay, so let's just take a look at this wording really quick. And again, this might not work for everybody, but it is just a tip if you struggle with figuring out what branch comes off of what.

Because remember, you identify really circ versus LAD first, and then you can kind of worry about these little things. So what comes off the LAD are diagonals K, D, and D. Haha, D&D if you play Dungeons & Dragons. And then what comes off the circumflex, I know this U isn't an O, right, but it looks more like an O than a D, are the obtuse marginals.

Okay, the O-M's come off of the circumflex. And that's the end of this video. I hope this helps at least with basic coronary artery anatomy for the LCA. Stay tuned for the RCA and more.

Transcript for:Understanding Left Coronary Artery Anatomy

Transcript for:
Understanding Left Coronary Artery Anatomy