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Complications after a heart attack (myocardial infarction)

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after you've had a myocardial infarct a heart attack you are prone to developing complications and a complication in this sort of context is essentially another disease or condition that crops up as a result of your myocardial infarct and most complications tend to occur within the first few weeks after having a heart attack so let's look at some of the major complications that can occur after after myocardial infarct and let's sort of do this in a stepwise fashion to make everything sort of flow logically in our heads so we can say that myocardial infarcts caused three major problems with our hearts right so so one of the things is they cause our heart to have decreased contractility because after a heart attack you've sustained some damage right to your to your heart muscle so it can't always contract very well you also get this electrical instability in your heart because all of the ions that sort of move back and forth across your heart muscle cell membranes to maintain your electrical gradient so your heart beats properly they all get really disrupted so you have this electrical instability and you also get tissue necrosis right you get death of some of your heart muscle cells so these three sort of effects of having a myocardial infarct they really underlie all the downstream complications that are possibly going to crop up so how does reduce contractility do that well if your heart's not contracting properly then you're not going to effectively be able to push blood out of your left ventricle too to the rest of your body right so you'll end up in a state called hypotension and the hypotension just means that you have pathologically low blood pressure when you have pathologically low blood pressure you're not going to be able to fill your coronary arteries with with enough blood all the blood that they need remember besides the coronary artery that's been blocked to result in your myocardial infarct there's still other coronary vessels that need to have a healthy supply of blood coming to them so that they can in turn supply blood to the rest of your heart muscle right the the heart muscle that isn't infarcted so if they're not getting enough blood then you'll start to get ischemia in the muscle in other parts of your heart and if you get ischemia and other part of your heart then that'll cause more of your heart muscle all over to not contract properly and eventually you might not be able to maintain your cardiac output at all and end up in a condition called cardiogenic shock and because this wall here and and we're assuming that it's this wall that's been sort of injured in the in the heart attack because this wall here isn't contracting very well you'd be predisposed to forming a thrombus a clot on the inside of that left ventricle there because when blood isn't constantly moved around as it might not be in that little area there it tends to clot and why is that bad well sometimes they can sort of flick off become separated off of the left ventricle wall there and travel through the aorta and into other vessels of the body where they might get stuck and cause an infarction in in another part of the body for example if one went up into your brain it might get stuck in one of your your cerebral vessels and cause a stroke so embolism is a potential problem embolism is the mobilisation of a thrombus a clot all right what about this electrical instability over here well the electrical instability can cause arrhythmias which is when your heart doesn't beat with a normal regular rhythm like it's supposed to and again that's due to a combination of things that's due to sort of disorganized ion movement within the cardiomyocytes and it could also be due to a disrupted electrical conduction system within the heart and and I should mention as part of this conduction system compromise ation here the two major pacemaker centers in your heart are located in your right atrium so you got your sinoatrial node about there and you have your atrial ventricular node around here and these two nodes are really responsible for for regulating the normal rhythm of your heart and so if you happen to have a myocardial infarct that affected the right atrium where both these nodes live you would probably end up developing an arrhythmia because you'd potentially knock out the two biggest regulators of your heart beat your heart rate and rhythm all right what about this tissue necrosis thing well remember necrosis just refers to death of something so in this case death of the heart tissue well remember after a myocardial infarct do you get a whole bunch of immune cells that come into your heart and try to sort of tidy things up after your heart attack and when your immune cells are involved with sort of tidying something up that's called an inflammatory reaction and you might start to get this inflammation around the outside of your heart I'm drawing this inflammation in as pink here pink is supposed to represent all those white blood cells as part of your immune system mediating this inflammatory response here on the outside of your heart now remember your heart sort of sits inside this fibrous sac it's encased by this fibrous sort of cover called your pericardium your pericardium peri meaning around and card iam referring to your heart and when you get all this inflammatory sort of stuff happening on just beneath the pericardium on the outside of the heart you could irritate your pericardium and you could end up with a condition called pericarditis now that's not all that tissue necrosis can do it can do some other pretty nasty stuff here so let's say that you start to get necrosis of your your septum here the wall that separates your left ventricle and your right ventricle well you can probably imagine that that wouldn't be very good at all your oxygenated blood in your left side of your heart and your your deoxygenated blood in your right side of your heart they would mix and you would probably end up with a pretty significant hypoxemia or low oxygen level in your blood a ventricular septal defect would also cause some damage to the arteries in your lungs because if you can imagine blood from this high-pressure system on the left side of your heart would sort of cross through this defect over to the right side of your heart and be pushed up through into your pulmonary circulation that's not good for your pulmonary circulation and can actually cause some pretty pretty big damage there what else will tissue necrosis do well what if you get that necrosis over on this side or really any other muscle that forms the outer outer wall of the heart well where do you think blood in the heart would go if all of a sudden there was no wall anymore it would just burst out of the heart so tissue necrosis can also cause a rupture of the ventricle but remember this pericardium we talked about this really tough fibrous sac that encases the heart the blood would then just get trapped inside the pericardium and it would start to sort of build up in the pericardium and track along the the outer heart muscle and the and the inside of the pericardium so that obviously would put a stress on the heart and prevent it from beating as well and you'd end up with a complication called cardiac tamponade tissue necrosis is not done yet though one of the more common issues that happens as a result of tissue necrosis is this here you've got these muscles in the bottoms of your ventricles called your papillary muscles and what your papillary muscles do is they sort of hold onto the the cusps of your valves the flaps of your valves using these structures called chordae tendineae they're these sort of tough durable string-like things and so the papillary muscles in the chordae tendineae work together to make sure that during a heartbeat when your ventricles contract your mitral valve and your tricuspid valve over on the right side you have a set of papillary muscles in chordae tendineae over there as well they make sure that the the cusps of your valves don't invert up into the atria and so sometimes after a heart attack one or more of these papillary muscles will become Nick roast it'll die off and when it dies off all of a sudden now the valve flap that it was holding onto can invert it can go up into the left atrium this means that when the ventricle contracts to push blood out into the aorta to get around the body blood can now get back up into the left atrium this is called having a leaky valve or a regurgitant valve in this case since it's the mitral valve we call this mitral regurgitation so just before we finish up let me just draw your attention to this if your heart has decreased contractility then it's going to have to work harder to maintain proper perfusion of your body with blood if you have a mitral regurgitation then again your heart's going to have to work a lot harder to maintain proper perfusion of your body with blood if you have a ventricular septal defect again your heart is going to have to start working a lot harder so these three conditions in particular if you develop any of these after a heart attack or not you run the risk of developing congestive heart failure which is when your heart just can't pump out enough blood to meet the oxygen needs of your body