Cardiogenic shock

- [Voiceover] The heart is a very beautiful organ and here I have drawn a cross section of the heart where you can see the various different compartments, you've got the right atrium, the right ventricle and the left atrium and the left ventricle. And the right side of the heart of course pumps blood to the lungs which would be on either side of the heart and this blood returns back to the left side of the heart through the left atrium and then blood is pumped again from the left ventricle out into the system all the way down to the legs and then up to the brain as well as the arms through the aorta. And of course, this entire process is essential for life, for delivering oxygen to the tissues, delivering nutrients, all of that. And so you would imagine, failure of the heart pump results in less output, less cardiac output which means less tissue perfusion. A patient would no longer be able to distribute all that oxygen. But what could cause failure? Well failure of the heart can result from valvular problems. So, for example if the aortic outflow tract which is right here is perhaps damaged or narrowed in some way, it's going to make it extremely hard for blood to be pushed out through the aorta and out to the system. So valvular problems can be a cause of failure that leads to shock, arrhythmias. Which means there's an issue with the electric conduction through the heart which allows it to function and pump our entire lines. There could potentially be stiffness of the ventricular wall or the wall of the heart which prevents it from being able to contract properly, and if the pump itself is so severely disabled this can lead to shock, lowering of the blood pressure and decreased ability to deliver the necessary oxygen to the tissues. And I want to highlight that heart attacks are the major cause of cardiogenic shock. So, MIs, myocardial infarctions cause decreased contractility. So, what you'll see is for example if we look at the left ventricle, if blood can't be pumped forward it will back up and it will back up into the left atrium. And when the heart can no longer accommodate all these fluid overload, it's going to backup into the lungs as well, each side of the lungs. And as things gets worse and worse, it will back up into the veins and all the way into the right side of the heart and it can be backed up all the way into the system as well. So this is really known as fluid overload and there are just a couple of symptoms that I'm going to point out. So for example, pulmonary congestion. Pulmonary congestion. Like I said, blood is backing up into the lungs and so that may make it difficult for patients to breathe and they may have a cough that's productive with a lot of fluid and that's really the blood backing up into the lungs. You may see something called increased jugular venous distention, that's JVD and jugular venous distention is basically the jugular vein gets distended because as you see here this blood backs up into the venous system and it can back up all the way into the neck. And of course, you might see chest pain, also known as angina. As the heart is starved for oxygen and then of course you may see the different symptoms that you would see in other shocks such as organ failure, organ dysfunction, decreased urine output and all of these is caused by decreased oxygenation of those different organs and tissues. And you will likely also see cool skin as blood is being diverted away from the skin and to more vital organ such as the brain or the heart and the lungs. So with these symptoms and these causes of heart failure, how can we diagnose cardiogenic shock in a patient? Let's take a look over here so we can take a look at the diagnosis of cardiogenic shock. And so diagnosis will include of course your typical labs such as serum lactate or ABG, assessing the oxygenation and the failure of tissues to utilize oxygenation for their biochemical needs. But also you're going to want to look at different things that might be causing heart failure. So for example, you might want to look at troponins which will show if there's any tissue damage or damage to the heart like in the case of a severe heart attack. Or maybe you can look at a chest x-ray. So here is a normal chest x-ray with the clear lung fields. You can see this diaphragmatic recess so there's no fluid accumulation here and here is a congested heart and lungs. You can see this kind of fluffy fluid accumulation where the pulmonary veins are. So, over here on our little heart picture the pulmonary veins are really congested because of the backup of fluid from the left side of the heart. And you can also see this sort of blunting of the diaphragmatic recess. Here it's still a little bit sharp but on this side you can see it's starting to blunt, get blunted a little bit. So you can kind of make out the outline of the diaphragm and where it meets the chest wall but it's somewhat obscured as compared to the normal view. And let me actually go ahead and erase that so you can see it again. You can see how it's still kind of obscured versus over here. Or maybe you might want to look at an EKG for different signs of arrhythmias or a heart attack or something like that. Or take it one step further and get and ultrasound it, echocardiogram to take a view of the heart. This heart ultrasound will allow you to see the contractility of the heart, how well it's squeezing blood. And so I highlight all of these really just to say that you want to look and see what's going on with the heart. What is the problem that's causing this cardiogenic shock or heart failure so that you can potentially correct it. But aside from these lab values, two ones that are particularly important in cardiogenic shock are evaluating the PCWP which is pulmonary capillary wedge pressure and the cardiac output. So here we are, let's zoom back down and take it over here. And look down here so we have a little bit more room to play around. And again, I'm gonna raise it a little bit. So first let's go ahead and tackle the pulmonary capillary wedge pressure. Now the pulmonary capillary wedge pressure is determined by inserting a catheter to go through the venous system into the right side of the heart and up into the pulmonary arteries to essentially the capillaries. And that's why it's called the pulmonary capillary wedge pressure. You wedge this pulmonary catheter all the way into the pulmonary capillaries. And the reason you do this is to assess back pressure from the heart. Remember in cardiogenic shock fluid from the left ventricle builds up and backs up into the lungs and into the pulmonary arteries. And so this backup of fluid actually creates a pressure whereas the pressure is normally less than 15 millimeters of mercury in the pulmonary arteries near the pulmonary capillaries. The pressure in cardiogenic shock will be above 18 millimeters of mercury. So this will be a way you can diagnose cardiogenic shock when you're trying to figure out what type of shock this may be. And the second thing that you can take a look at with the heart is cardiac output. Now, I had mentioned cardiac output or cardiac index and cardiac index might be a word that you haven't heard before, don't really understand what it is. Well, cardiac index is essentially the cardiac output over a patient's body surface area. And cardiac index is really used to standardize cardiac output. The idea here is that patients come in many different shapes and sizes. They can be very tall like NBA players such as Michael Jordan and Kobe Bryant or normal sized, a little bit smaller than a basketball star or even shorter like children for example. So, with different heights and weights of patients, cardiac output varies and that's why you can use body surface area to really create a standard value that can be used in place of cardiac output. And cardiac index in patients with cardiogenic shock will be less than 2.2 liters per minute. So that's cardiac output over meter squared and that comes from body surface area. And the normal of cardiac index should usually be between 2.6 and 4.2. Now there are actually many different ways to measure cardiac output including pulmonary artery catheter. You can also use an echocardiogram to look at the heart but it's important just for you to know that cardiac output is an important measure to obtain in a patient who has cardiogenic shock. Now for the treatment of cardiogenic shock I like to break it down into three different things. First of all, remember in shock, patients are lacking oxygen delivery. So providing a patient with oxygen will provide added support so that their cells can receive the oxygen they need. And number two, you need to provide cardiovascular support. So the cardiovascular system is in trouble and needs a little bit of help. So there's two ways to think about doing this. First, you could increase the systemic vascular resistance. So that means blood vessels will be able to carry blood forward a little bit better if the resistance is increased. And this can be done with different medications called vasopressors, norepinephrine, epinephrine. They're all examples of vasopressors. They allow blood vessels to squeeze down to improve blood flow. And another way to improve cardiovascular support is through increased heart contractility. If the heart can contract better then it can squeeze out the blood. In fact, that's the problem with cardiogenic shock. Blood is not getting pushed out of the heart. So improving contractility and there's different medications for this as well, but improving contractiility is another thing that can be done to treat cardiogenic shock. And finally, the last and probably most important thing to do is to repair the heart or whatever problem is causing the cardiogenic shock. So for example, in a patient who has occluded blood vessels in the heart, there's a procedure to restore blood flow by opening up those vessels and allowing oxygen delivery back to the heart. Or maybe as i said before, a valve is the problem so repairing or replacing that valve may be what helps solve the heart failure. And in some very severe cases, replacing the heart entirely, performing a heart transplant may be the only way to treat this cardiogenic shock. So remember, in cardiogenic shock, the issue is the heart itself is not pumping and does not squeeze enough to allow blood flow to go forward and this results in poor oxygen delivery to the rest of the body.