Episode Summary

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 of course welcome to the Healthy Heart Network. Today I'd like to talk a little bit about when the heart's not working properly, when the heart's in cardiac failure, what starts to go wrong? Because there's a real cascade of consequence. which ends up in calamity for people with hearts that are just not working properly. I've already spoken about this a little bit before, but I would like you to try and understand that the responses of the body are the evolutionary responses that we evolved with millions of years ago to deal in that situation with blood loss. So our evolutionary past was to deal with if we got injured and our circulatory volume was diminished by bleeding. We didn't evolve millions of years ago to deal with cardiac failure because, of course, our ancestors millions of years ago who had cardiac failure just died. So there wasn't a way for them to evolve to deal with that issue. So the issues that we see with cardiac failure in this millennium are related to the evolutionary responses from millions of years ago. So let's think that through. Let's start with the heart not working properly. With the heart not working properly Not enough output is going to the body. This turns on what we call a neuro-humeral response. Neuro being related to nerves, humoral being related to messengers within the blood. So the lack of cardiac output through the heart not working properly gets registered as a lack of blood volume. by organs within the body, in receptors in the main blood vessels, like the carotid arteries in the aorta, but also receptors in the kidney. That neuro, nerve-based, humoral response says, wow, we've lost blood. We need to preserve what we can. We need to make sure we get that blood volume back. So there is a response where the signals to the body are then to constrict blood vessels so that the blood pressure remains elevated because the body's thinking it's lost blood and therefore going to drop blood pressure. So the body responds by constricting blood vessels in the periphery to keep the blood pressure up. The other thing it does is it starts to retain fluid. to replenish what it perceives to be the lost fluid from the bleeding out. Of course, that constriction of the blood vessels and that retention of fluid then feed back to the heart, which then gets loaded more and more. I'll also mention that part of that neurohumeral response is a sympathetic overdrive, that flight and fight response. so if you've ever been frightened you'll know that the other thing that happens is that your heart races so now we've got a body responding to a heart that's not working properly by increasing the blood the tension in the blood vessels to keep the blood pressure up so vasoconstriction it's retaining fluid so increasing blood volume and it's also making the heart race well this of course for a heart that's not working properly loads it even more it then causes this feedback and so the heart is now having to deal with more volume coming back to it the heart is having to deal with going faster the heart is having to do with pumping against a peripheral vascular resistance or an increased blood pressure because the blood vessels have constricted and you can imagine that under this load the heart may not be able to keep up the cardiac output it needs to and so the neurohumoural response, the nerves and the senses within the body think it's getting worse and this vicious cycle continues. We know that other things can feed into this and come out, feed into this and occur as a consequence of this. Certainly things that can feed into this are other conditions like atrial fibrillation which can really put the heart under load if it's already strained. We also know that things like coronary artery disease are common associations of cardiac failure and certainly commonly seen as people get older and that of its own can impact on how the heart works. But cardiac failure of its own can have lots of other consequences. The lack of blood flow out to the tissues means that things like skeletal muscle just don't get the blood they need. And so the muscles are fatigued. Cardiac failure of its own through the inflammatory response of the sympathetic nervous system changes some of the proteins that are available for iron absorption. So the body stops absorbing iron as efficiently. As the body stops absorbing iron efficiently, then the iron that's needed for the heart function is no longer there and the heart function drops off. But the patient can also develop anemia, which again can worsen the situation. With poor cardiac output, the kidneys can suffer because kidneys always need good blood flow going through them to keep a good filtration rate going. We also know that as the heart fails to work during the day, it also fails to work during the night. And so patients with bad hearts can get bad sleep, therefore altered memory, confusion, they can even get depression. This terrible cycle of the heart not working properly and then the body's responses, driving responses that can make, that can worsen the problem and feed back is really what we need to understand in terms of the downward spiral that can occur with cardiac failure and understand in the context of some of the interventions that we want to put in place to try and treat and support people with cardiac failure. So it's a little bit complicated but very important. Heart doesn't work properly. Neurohumeral response, a fight or flight response. which drives increased blood pressure, it drives increased heart rate, it drives fluid retention, it even drives inflammation and the whole cycle feeds back on itself. A complicated beast is cardiac failure but it's really important that you have a little bit of an understanding of where some of those points of action are because When we talk about treating cardiac failure, we'll be talking about dealing with some of those responses and how we avert them to try and protect the heart in the longer term. I hope you've enjoyed this presentation on what goes wrong in cardiac failure. If you have any queries or questions, please drop us a note. If you have any thoughts about future podcasts, please let us know. And of course, until next time, I wish you good health. Goodbye.