Myocardial Infarction (MI): Pathophysiology (Nursing)

00:00 Hi! Welcome to our video series on acute coronary syndromes.

00:05 Now, we're going to talk about MIs, Myocardial Infarction and help you differentiate between a stemi and a non-stemi.

00:12 So this is going to be really fun, hang with us.

00:15 Now a myocardial infarction.

00:17 This is just a quick review for you because I know, you probably already know what this is, but humor me as we walk back through it.

00:24 Now. You see in our graphic.

00:26 We've got a little area there and you see the blood supply of the heart.

00:30 I encourage you if you haven't spent time studying that to really refresh your memory or learn it for the first time.

00:36 But either way, it's important you understand the location of those vessels.

00:41 You'll see on the drawing how their kind of pinking color that means blood supply is present there.

00:46 But in the part we've zeroed in for you see that there's not blood supply down by that tissue that's been infarcted.

00:54 Because there's a blockage that's what a myocardial infarction is, but I want you to keep an eye on these drawings as we go through this presentation, because we've done a really good job of helping you visualize what the average heart looks like.

01:06 So you've got it there.

01:07 It's a localized area of necrosis, dead tissue in the heart.

01:12 You can tell in the drawing that there's not blood getting to that tissue and that's why it's dead.

01:17 Now it's caused by an occlusion of a coronary artery.

01:20 That's what you see blown up there.

01:22 You can see the plaque that's formed on both sides and included the artery.

01:27 And when that happens, you can't get enough oxygen to the heart and that that is why the tissue dies.

01:32 Now if this makes perfect sense to you, just celebrate.

01:36 Your learning stuff all the time.

01:38 And as you continue to put the pieces together, it's going to be more and more fun as you can apply that to clinical practice.

01:45 Now with anything stroke or a heart attack, Time is tissue! And the faster we can re-establish that blood flow the better chance we have of minimizing irreversible death of those cells.

01:58 Usually takes about 20 minutes of the artery being blocked, for the tissue to begin to infarct or to die.

02:05 So we've got about a four-hour window the onset of pain of symptoms that the tissue can be salvaged.

02:12 Now If you've heard us talk about thrombolytics, there's a four-hour window within symptom onset when that medication has to be administered.

02:20 This is why, because if we can restore blood flow within a four-hour window, then that tissue is more likely to be salvaged after four hours, we I really don't have much of a chance which is why we don't give thrombolytics because they're a high benefit drug, but they're also high risk since they, boom, blow up all these cloths anywhere and indiscriminately.

02:44 So let's talk about how we name MIs.

02:47 This is why I really stressed with you.

02:49 It's important that you understand how the blood supply works.

02:53 Now this is in a textbook heart.

02:56 I know I've worked when you see patients results after a heart cath.

03:00 Not everybody's blood supply looks exactly like this but this is the general idea.

03:05 So I want you to take a look and orient yourself on the graphic.

03:09 You see where the aorta is you have a feel for, all those vessels are going out to the rest of the body.

03:14 We've got the atrium on the top, the ventricles on the bottom.

03:19 Now locate the left coronary artery.

03:22 Can you see that there? Okay good.

03:24 We're going to walk through how some of these work.

03:28 So underneath there, We've got these circumflex artery now that's going in between those vessels that you see right near the top left circumflex means it's going to wrap around the heart.

03:41 Now if we have a blockage in the left circumflex artery, it's going to be a lateral or a posterior MI.

03:48 Now in the drawing we've kind of tried to show you in this graphic how it wraps around.

03:54 So you'll see as the vessel comes around the back side of the heart.

03:57 It's got a dotted line, and the artist did that for you.

04:00 So you have a 3D picture in your mind of how these vessels wrap around the cardiac muscle.

04:07 So spend some time.

04:08 Make sure you come back and really look at these, if you're not clear, if you can't name these vessels from your memory without looking at notes just write yourself a reminder to come back and really dive in spend some time here and make sure you're very clear and where these vessels are.

04:25 So we talked about a left circumflex occlusion.

04:28 That means I've got a blockage in the left circumflex artery, but here's the Widowmaker, left anterior descending occlusion.

04:37 Find that on the graphic.

04:39 So you see that there look what it feeds its the Widowmaker because it has the highest mortality rate.

04:46 It's an anterior wall damage that's going to really take out your left ventricle and that's why it's such a significant heart attack.

04:57 All right, you found the left circumflex.

04:59 We talked about occlusion there, and how that normally wraps around the back of the heart, and you can see that with the dotted line.

05:05 We've talked about the Widowmaker and you found the left anterior descending artery if that's occluded, We have a significant impact on the left ventricle, which is responsible for pushing blood out to the rest of the body.

05:20 Now finally, we're going to wrap up with the right coronary artery so find that in your graphic.

05:26 There you go.

05:27 So a right coronary artery occlusion is inferior wall damage.

05:32 So we've used some different terms here, lateral, posterior, anterior and inferior.

05:38 Make sure you have clear in your mind.

05:39 If you see those words used and that verbiage that you know, which artery is involved.