Cardiac Pathology: Overview

00:00 This is going to give you a big overview of cardiac pathology. It's actually possible to bin to compartmentalize the different cardiac pathologies into about 6 different categories. And if you understand kind of the big picture, the little picture just ends up being some details that are kind of cool but not as important as the big picture.

00:23 With that introduction, we're going to see a lot of cool videos that were prepared with the assistance of Dr. Jose Mata who I am eternally grateful for for all of his help.

00:34 Okay. So, this is the normal heart. What this normally doing is squeezing blood out in a controlled regulated fashion, in a rhythmic fashion, to provide perfusion to the lungs so that blood can get oxygenated but also to the aorta now to the rest of the body to provide oxygenated blood and metabolic nutrients to the rest of the body and eventually bring back venous blood that will allow us to get rid of various waste products and also carbon dioxide. So the heart in its beauty is just squeezing in a regular fashion and it's going to be coordinated. There's a lot going on here. What's not shown yet are their valves that are giving us unidirectional flow. There are coronary arteries that are providing adequate perfusion to the heart and then there are all the big vessels that are responsible for carrying blood to various places. Okay, that's what it should look like.

01:36 We're going to have some big picture of things related to cardiac pathology. Number 1 on the hit parade is pump failure and basically this can be due to a variety of causes but most commonly this is going to be due to a ischemic heart disease, a big thrombosis of a coronary artery which causes lost of perfusion to a part of the heart and that heart is not pumping anymore so there is pump failure. In this particular image, the right ventricle is fine, it continues to pump but the left ventricle is pretty much at a standstill.

02:13 That's clearly not going to provide adequate perfusion blood supply to the rest of the body. So that's one major mode of cardiac pathology, pump failure. What's shown here is actually a heart attack, but you can also have the same failure mode if you have myocarditis, you have inflammation and other injury of the heart. You can have pump failure if you fill up the heart with an extracellular component called amyloid so there are a variety of ways that you can have pump failure. Okay, that's one. Next one is because the valves that are supposed to maintain unidirectional blood flow don't work appropriately. So we're looking down on to the top of the heart and right there in the middle looking proud is the aortic valve. That valve should open all the way up to allow blood to flow out when the ventricle squeezes. In this case, we have a stenotic valve.

03:10 We have flow obstruction. That will have a number of consequences including diminished perfusion of all the distal tissues, but also the heart is going to have to work much harder to try to pump against that tight valve. So flow obstruction is another major cardiac pathology. Well, if you have stenosis, you can also have regurgitation. So the next one is regurgitant flow. This is looking at an aortic valve. Blood should only be going out through the aorta. It should not be going backwards into the left ventricle. That backwards regurgitant flow is going to cause volume and pressure overload in the left ventricle which eventually will translate back into the left atrium into the lungs and we will have heart failure. So, regurgitant flow is also a major source of cardiac pathology.

04:03 You can have shunted flow. So again, blood is supposed to go from the inferior-inferior and superior vena cava into the right atrium into the right ventricle and out the pulmonary artery, return through the pulmonary veins to the left atrium to the left ventricle and out through the aorta. But in a number of congenital heart diseases and sometimes acquired diseases you can have abnormal flow from the left side to the right side.

04:32 In general, that will be, as we'll talk about, the most common defect because left-sided pressures are much higher than the right-sided pressures if we make holes between the ventricles or between the atria, flow will tend to go left to right. There are exceptions to these very important exceptions when pulmonary pressure becomes very high.

04:53 But shunted flow is also going to cause significant pathology and in this particular case that extra volume and pressure coming from the left ventricle through ventricular septal defect into the right ventricle is going to cause pressure volume overload in the right ventricle causing, one, right heart failure but increased pressure and volume in the pulmonary circulation which can eventually cause pulmonary hypertension. So shunted flow is your 4th big picture cause of cardiac pathology. There can be abnormal cardiac conduction. So, if the atria do not transmit the signal appropriately from the sinoatrial node to the atrioventricular node, then you will have atrial fibrillation and then you will not have a coordinated squeezing of the atrium into the ventricles. Similarly, if the ventricle is quivering in ventricular fibrillation, that's another cause of cardiac pathology.

05:54 So the conduction system has to work appropriately and we will talk in one of our sessions together, you and I, about cardiac conduction abnormality specifically. And finally, we can have rupture of the heart or a major vessel and basically when that happens you get exsanguination. That seems like a rather trivial cause of cardiac pathology but can have major outcomes basically it's a cause of death. And what we're looking at on this image is a reconstruction of a patient with a dissecting aneurysm that was ultimately lethal because the blood got into the abnormal falts lumen and then ruptured out into the pericardial sac causing tamponade. Alright, with that, we have covered the 6 major modes of cardiac pathology and now in the subsequent talks that we're going to have together, it's just going to be interesting details.