Welcome to Dr. Warrick's podcast channel. Warrick is a practicing cardiologist and author with a passion for improving care by helping patients understand their heart health through education. Warrick believes educated patients get the best health care. Discover and understand the latest approaches and technology in heart care and how this might apply to you or someone you love. Hi, my name is Dr Warrick Bishop and welcome to my podcast and videocast channel and welcome to the Healthy Heart Network. Today I'd like to speak a little bit about cardiac failure and how we think about the causes of cardiac failure. Before I... start with breaking down the causes of cardiac failure. What I'd really like to do is a very quick recap on how we understand the circulation. First of all, what I'd like you to imagine is that we are dealing with a closed loop, if you like, a bike inner tube with fluid in it. At 12 o'clock, we're going to put the lungs in there. and i would like you to imagine that the fluid goes around in a single direction here's a rough idea we've got the lungs at the top or 12 o'clock oxygenated blood goes out to the tissues the organs goes through the capillaries and then circulates completing that loop back to the heart to go into the lungs again so that carbon dioxide can be blown off and oxygen absorbed and that blood go through the same journey and cycle around. Now for that to work, or for that to be able to occur, there needs to be some one-way valves and there needs to be some compression within that system so that the squeeze, which is of the heart, Shoots the blood in one direction as dictated by the one-way valves. So let's look at that very quickly or imagine that very quickly. Circulation again. Imagine that the lungs are at the top of that circulation. The lungs drain into the left atrium which gives the blood a squeeze. Into the left ventricle there's a one-way valve so that when the left ventricle squeezes blood doesn't go. backwards into the left otrum it goes forward and goes out into the body to the organs through into the capillary beds where it is able to provide oxygen and nutrients to the tissues the blood passes through the capillaries and is collected into the veins the veins all come together so that two major veins one draining the top half of the body the superior vena cava and a vein draining the bottom half of the body the inferior vena cava come together and drain directly into the right atrium or the right receiving chamber of the right side of the heart that gives blood a squeeze which pumps blood through the tricuspid valve which is a one-way valve into the Right ventricle, the right ventricle, then pumps blood into the lungs through a one-way valve called the pulmonary valve. You can see there's contraction occurring in the circulatory system and blood heading in one direction. Then the cycle is repeated. I've covered some of this in a little bit of detail before, so I'm going to cover it reasonably quickly. Remembering that components... The lungs and the heart are within the thorax so that the action of breathing also has an impact on return blood flow. Imagine you take a deep breath in, then the blood outside of the thorax is drawn towards the chest cavity through that negative pressure. Makes sense, doesn't it? That negative pressure assists blood coming back into the thorax. It therefore assists blood as we breathe out, going out of the thorax and supplying all the different organs through each of their specific capillary beds. Now what I'd like to do is talk, with that as a backdrop, is talk more about how the heart can fail and where we try and understand where those problems occur. imagine a simplified circulation what we're going to deal with is simply the right atrium contracting to fill the right ventricle contracting to pump blood into the lungs blood draining from the lungs into the left atrium that squeezing and pumping the blood into the left ventricle then the left ventricle squeezing and pumping blood around the body to the organs and the capillary beds and so on. If we think in terms of how the heart can fail, there are a number of ways, or there's only a certain number of structures, that can go wrong. In a very simple way, the muscle of the heart can go wrong. So things can actually affect how the muscle works. We can also load the heart. in a particular way that can cause failure. Lastly, the heart's electrical system may be playing up so it might go too fast or too slow such that the regulation of the heart rate is not matched with the cardiac output required by the body and hence we get failure. Let me give you a little bit more detail about that because that is really the topic of this presentation. When we think about the heart muscle being damaged, the most common thing would be coronary artery disease or lack of blood flow to the heart. We also see toxins affect the heart. We can see infection or inflammation affect the heart. Different substances can infiltrate the heart and stop that muscle working properly. We know that metabolic problems can also affect the heart. And we know that genetic issues, things that people can be born with and can be expressed as they grow into older life, can also affect the heart. When we think about loading of the heart, blood pressure can be a problem, but so can problems with the valves. So can congenital problems associated with loading. Also, if you put too much fluid into this circulation, you can overload the circulation. And if you increase the requirement from the body, if you have a high output state, then that can also put the system under load. I'm going to discuss some of these issues in a bit more detail. problem or being affected and causing the problem in the first instance imagine that the left ventricle for whatever reason is just not pumping well enough to get blood out of the heart and into the circulation well coronary artery disease or ischemic heart disease is probably one of the most common causes we see of that coronary artery disease may give rise to a heart attack and a heart attack will damage heart muscle and will leave a scar. If you scar a muscle, then obviously you reduce its functional capacity. So damage, which is permanent, giving rise to a scar, particularly if it's a large scar, will of course impact the way that muscle or pump works. Coronary artery disease can also affect the way the heart contracts if the muscle is still alive but not receiving enough blood. If the muscle is still alive but not receiving enough blood, then under increased load, the lack of blood supply relative to the need of the heart means that that muscle literally gets a cramp. It literally doesn't get the oxygen and nutrients it needs to function properly. Now you may have had or you may have known through watching sport on TV that people get cramps with intense exercise in their legs. This is when they're... muscles fatigue and they really need to recover and they're not getting the nutrients they need for the work they're doing. If there's a lack of blood supply to the heart then the muscle literally may cramp in the region that is not receiving adequate flow. That cramping does two things. One is it can give rise to pain but not always. Secondly, though, that cramp means that the heart is stiff. And if the heart is stiff, then that change in its ability to relax and its ability to be compliant will have an impact on the way the pump works. Let's think about that for a moment because it's a really important concept. I've explained that if the heart is scarred, there may not be enough muscle to pump forward out. through into the aorta to circulate around the body providing the output that's needed. But this is a little bit different. The muscle looks to be okay, but under load it stiffens. Now imagine if the left ventricle stiffens and the flow, the circulation continues to pour into that left ventricle as usual. or restricted left ventricle, will not dilate and will not receive the amount of blood that it should, that it needs to, to maintain cardiac output. So that blood literally gets pushed back to the chamber before the left atrium and then gets pushed back even further into the lungs. So stiffness of the heart... which can be through lack of blood supply, but it can be through other things, which I'll cover in just a little bit of time. Stiffness of the heart, or what we call failure of relaxation, and we also call it diastolic dysfunction, can give rise to raised pressures because it's not dilating properly. Those raised pressures can be transferred back into the left atrium, straight back into the lungs, and if you've got increased pressures in your lungs and increased blood volume in your lungs, guess what? That causes sureness of breath. So diastolic dysfunction from lack of blood flow and relative cramping of that myocardium. Diastolic dysfunction is really important. I'm going to touch on it in other aspects as well. Toxic changes can also affect the function of the heart. We know that recreational drug use, such as cocaine, And even anabolic steroids can damage the heart muscle. But really importantly, and probably most commonly, is the use of excessive alcohol, which we know can damage the heart muscle, leading to it just not working properly. Different metals can also damage the myocardium, myocardium being the heart muscle. We know that too much copper, too much lead, too much coal, though. cobalt and even too much iron can all have an impact on the way the left ventricle and right ventricular muscles work and this can have a significant effect on the way the heart pumps. Some of our medications can also be directly toxic to the heart muscle particularly some of our chemotherapeutic agents. There are some other agents like antidepressants and antipsychotics and immune modulating drugs but probably The group of drugs we're most concerned about, we monitor the most, are some of the agents used for treating cancer, which although they kill the cancer cells or manage the cancer cells, can have a detrimental effect on the way the heart muscle works. One of the other things that can directly affect the heart muscle is radiation. So certain situations where patients may need radiation of the chest for different sorts of tumours, may also impact the heart and that's important to be aware of. One of the other things that will damage the way the heart muscle works is if it's inflamed. Inflammation can be from infection and there's all sorts of infections that can give rise to problems with the heart muscle and there's a whole panel that we often check, things that include bacteria and viruses. And in certain parts of the world, even parasites, a thing called Chagas disease in South America, can give rise to altered or diminished or worsening function of the heart muscle and give rise to cardiac failure. One of the other things that can give rise to inflammation within the heart muscle are what we call autoimmune disorders. And these are disorders where the body's immune system, for whatever reason, tends to turn a bit against itself. Such conditions include things like rheumatoid arthritis and systemic lupus erythematosus. You may have heard of these conditions, but they may affect the heart as well. We're still looking at things that may impact the way the left ventricle works. And one of the things that can also happen is infiltration of substances into the myocardium to alter the way it works. Unfortunately, one of the ways that that can occur is if malignancy, so local malignancies, perhaps from the esophagus or lungs, directly infiltrate into the heart muscle. Metastases from other tumors can also... infiltrate into the heart muscle and you can imagine that if there's other tissue within the muscle or replacing the muscle or eating the muscle away it can alter the way that the left ventricle or right ventricle are working and of course therefore give rise to failure. Another way that things can infiltrate though is through deposition of certain proteins and there is a group of proteins called the amyloid proteins. which are generally a consequence of different metabolic processes going wrong within the body, either within the liver or within the bone marrow, where excess specific proteins are produced and those proteins can deposit into the left ventricle. If more and more of these proteins get deposited into the left ventricle, they form an array. get in between the muscle cells and stop the muscle cells working properly. They make the heart stiff and they don't allow it to relax. They give rise to diastolic failure. These sort of proteins, amyloid proteins, are very difficult to treat, but there are some promising changes in recent times which give us the opportunity to think about whether we can intervene with that sort of process. There are also some genetic conditions where... either too much fat or too much glycogen is deposited in the heart muscle because it's not dealt with properly by the metabolism of the individual. These are very specific conditions and would be really the sort of thing that a specialist in cardiology would be able to deal with. For our situation, simply knowing that Too much fat or too much glycogen or even the wrong sort of proteins deposited in excess into the heart muscle tissue will of course affect the way it works. Metabolic problems can also impact the heart. Things like the thyroid not working properly will directly affect the heart muscle. So will problems with the calcium being too high or too low. This can come about because of... parathyroid abnormality. Growth hormone abnormality can also directly affect the muscle. Further to that we know that things like nutritional issues can impact the way the heart works and lack of vitamin B1 or thiamine has historically been called wet beriberi because the lack of that vitamin leads to failure of proper heart function, dilation of the heart, retention of fluid and development of cardiac failure. Other nutritional issues can be multifactorial nutritional problems from malnutrition or malabsorption even and iron deficiency. The last group of... The last group of... mechanisms to deal with heart muscle problems are the genetic group and there are a number of these which can lead to the heart being too thick and therefore too stiff or the heart literally developing failure dilating and not working properly as the individual grows and develops and expresses that genetic predisposition there are also a group of genetic conditions called muscular dystrophy is where multiple muscle groups within that individual are affected and the heart is equally affected so there you go direct problems with the myocardium or the muscle of the heart the next group of causes of heart failure are really related to abnormal loading of the heart. This means that there's some sort of pressure problem that is leading to the cardiac failure. The most common of these is high blood pressure, and if you think about it, increased blood pressure in the circulation that the heart is pumping against is the direct work that the heart has to do. Long-standing hypertension means the heart has to change to deal with that load. And that load makes the heart thicken up to work harder, but then it makes it stiffer. And we've already talked about stiff hearts not relaxing properly and just not doing the job properly. Stiff hearts fail during the time that the heart should be relaxing. We call that diastolic failure. So hypertension, an incredibly important contributor to loading the heart. potentially being a cause for heart failure. If you think about it, if any of the valves are affected, then this can load the heart as well. Imagine the aortic valve being too narrowed so that the left ventricle has to pump hard and hard and hard to get... blood out of the aortic valve around the circulation so this increased load on the left ventricle is a little bit like the effect that high blood pressure would have. Imagine though that the aortic valve instead of being stiff leaks and if that aortic valve leaks then every squeeze out blood will leak back in and so the cardiac output will be diminished by the amount of blood that's leaked back in from the aorta into the left ventricle well over time the heart tends to try and accommodate that by dilating the left ventricle so that it gives a larger squeeze out a larger volume with each squeeze so that some can regurgitate or fall back into the left ventricle but enough because it's compensated goes forward to deal with the requirements of cardiac output for the body. If you think about any of the valves in the circulation, the aortic, the mitral, the pulmonary and the tricuspid, any of these leaking and allowing reverse flow or being tight, or stenotic is the word we use, limiting forward flow, will have an impact on the circulation. circulation and the impact will be both in the forward direction leading blood out towards the body but also be in the reverse direction meaning there'll be congestion behind where that abnormality is we've talked about the heart muscle on the outside of the heart there's a special covering called the pericardium If this pericardium thickens up, it can restrict relaxation of the heart muscle and literally act like a restrictive chamber around the heart. This can give rise to failure. The inside of the heart also has a special lining. So within the myocardium, within the muscle layer, there's another layer called the endocardium. Believe it or not, this can also be affected by disease processes. And if this is stiff and thickened, it can also affect how the heart relaxes and therefore give rise to cardiac failure. We know that if the body's requirement is for lots and lots of cardiac output, then the system can be overloaded. A bit like running your car into the red zone. when it comes to your revs so revving your car into the red zone on a long-term basis we call this high output failure where the body's requirement is so high that it drives the heart to provide extra blood through the circulation things like anemia so a lack of red blood cells in the bloodstream mean that not enough blood is getting out to the circulation. So the body asks for more. But the other thing is that with anemia, there's a change in the viscosity of the blood. And the blood literally flows faster through the whole circulation. And so it speeds it all up. This is a high output state. So anemia can give rise to failure in that situation. So can sepsis. So a bad infection can speed up the whole circulation. So can thyroid dysfunction. So if the thyroid activity is increased, it stimulates what we call the sympathetic nervous system, which is our accelerator, the body's natural accelerator, and speeds up that circulation as well. And even a condition called Paget's disease at the bones, where the bones become hypermetabolic and their demand for blood increases. and so the circulatory demand increases as well. The other thing that can put load on the system is literally fluid overload. So if we think about this being a closed state, and let's say there's five or six litres of blood volume circulating at any given time, if we increase that five or six litres fairly quickly, to say seven, eight, nine or ten litres, then that fluid has to go somewhere, and it puts the whole system... under pressure one way of getting fluid overloaded is if your kidneys don't work if you keep taking fluid in but your kidneys are not producing fluid and letting it go then that will lead to increased fluid accumulation in the circulation and that will have consequences on the heart with pressures increasing through not only the circulation but through the right side of the heart the lungs and the left side of the heart One common way that we see people fluid overloaded is through times in hospital where we give people fluids, sometimes during surgeries, sometimes when they're sick. We can sometimes over-replace fluids. We call that iatrogenic. It is an important thing to be aware of and we always monitor it because we are aware of the significance of giving people too much fluid. Lastly, we've talked about the muscles. We've talked about the loading. Lastly, let's talk about the speed that the heart goes. It can go too fast or it can go too slow. If it goes too fast, obviously, we end up with a picture not dissimilar to a hyperdynamic circulation, but it can be driven by the electrical system of the heart and sometimes we see this in different conditions particularly for example a condition called atrial fibrillation and if that's poorly controlled rate wise the heart can race along at over 120 130 beats a minute for a prolonged period of time and with that prolonged rapid heartbeat the heart can eventually decompensate and go into failure Unbelievably, if the heart goes too slowly as well, then the cardiac output is just not enough for that individual, and with time, that heart will fail as well. The patient may in the meantime also. So I've covered a lot of stuff there in terms of what may lead to cardiac failure. There are a lot of things. It can be problems with the muscle. It can be problems with loading of the heart. It can be problems with rate of the heart, too fast and too slow. There are some really important ones to take away. Coronary artery disease is a really important one, both if it's caused a scar or if it's leading to lack of blood flow, literally giving cramp and diastolic dysfunction problems. Toxic is really important, particularly if we think about alcohol, because that is... a little bit self-inflicted and can be altered. I think it's really important to remember hypertension. This is one of the really big and significant contributors to heart failure, particularly heart failure where the heart appears to maintain normal structure and seems to pump well but doesn't relax well. We also need to be aware of fluid overload, particularly in the hospital setting. So there's a lot there. I hope that you get an idea of all the complexities that we need to follow through when we're dealing with trying to figure out what causes cardiac failure, because if we can tease out what the primary causes are, it gives us something that we may well be able to treat. I'm going to wrap it up there. I hope you found this informative and educational. If you have any queries or questions, as always, please drop us a note and let us know. If you have any ideas for any further or future podcasts or videocasts, please also let us know. For now, I would like to wish you the very best and goodbye for now. You have been listening to another podcast from Dr. Warrick. Visit his website at drWarrickbishop.com for the latest news on heart disease. If you love this podcast, feel free to leave us a review.
