Welcome, my name's Dr. Warrick Bishop. I'm a cardiologist, I'm an author and a keynote speaker. I'm CEO of the Healthy Heart Network. I'm all about trying to help people live as well as possible for as long as possible. Heart disease is huge in Australia. Every 20 minutes someone suffers a heart attack. Most of these could probably have been avoided if only we knew what to do. This podcast is all about helping you understand blood pressure, weight, cholesterol for better health. If you enjoy this podcast, I would be honored for a five-star review. You can share it with your family and friends. It may well save someone you love. Hi, my name is Dr. Eric Bishop and welcome to my podcast and videocast station. Today, I'm going to share with you a little bit about heart rate variability. Well, I have to confess. that I've been hearing bits about heart rate variability for some years. We don't tend to use it routinely, clinically in my practice, but it does pop up a fair bit, a fair bit in social media, and obviously we're getting more and more devices and wearables that will give us some insight into heart rate variability. So I thought I'd quickly do a bit of research and get the load down on it and share it with you. That would be a way for me to learn it at the same time. Well, as I started to look into it, it occurred to me that this heart rate variability thing is far more complicated than a simple soundbite, which is heart rate variability. Good or bad. So let's talk a little bit about it. Let's share with you what I don't understand about it. And let's open the door to what the future may offer in regard to looking at it. So the concept of heart rate variability is really around recognizing that there can be very subtle and minor changes in the interval between consecutive. heartbeats, and they call that an inter-beat interval. And you can imagine that that's not too surprising. We are, after all, a biological system. There would be variation in that, and that biological system, if you think about it, has all sorts of interplay, and not least of which is the nervous system that runs into the heart and has some sort of input by release of chemicals onto the surface of the heart, into the cells of the heart, to define how the heartbeat might go. Well, it turns out that there is almost constant variance in the beat-to-beat interval. So it is constantly changing and it changes throughout the day. When we look at heart rate variability, we have to be aware that we need to consider over what period of time we're assessing it. And that means that we can only compare apples with apples. So in general terms, heart rate variability tends to be assessed over a 24-hour period with particular devices, over a five-minute period with particular devices, or less than five minutes. Well, of course, that's important because if you're going to compare, You have to compare the same length of observation with the same length of observation. Well, when we talk about that heart rate variability in the intervals between beats, what does it relate to? Well, I've already alluded to that the brain has an input and an impact on the heart. Also through the automatic or autonomic nervous system. Now the automatic or autonomic nervous system is the one that acts in the background when we are thinking about something else. Remember the autonomic nervous system is divided into the fight and flight mode. So if we're suddenly confronted with a sober tooth tiger. Our eyes dilate so we can see better. Our heart races so we've got more blood going to the body. The blood vessels to our legs open up and we are ready to run or fight. So that's the sympathetic nervous system or the fight and flight response. Remember the counter to that is the rest and digest nervous system. We call that the para. sympathetic nervous system. That one will slow our heartbeat. It'll constrict our eyes. It will send blood to our guts so that we can digest and will often lower our blood pressure as it slows our heartbeat. So we've got these two different ends of the spectrum where the autonomic nervous system can come into play well of course the heart itself may have some beat to beat variance depending on the ions locally present within the cells and any other local influences because of that interplay that's constantly occurring between the heart the brain our conscious thought and the autonomic nervous system which has fight and flight rest and digest because of that constant interplay This reflects an environment for the heart that's constantly changing and therefore heart rate variability reflects the potential for adaptation of the heart to that changing environment. So when you hear the term that we need people to have good heart rate variability, what that's telling us is... By having good variability, it can quickly accelerate or decelerate as the body needs. So that heart rate variability is closely linked to our autonomic nervous system balance, can of course be linked to our blood pressure. It's also linked to gas exchange, how well we are moving oxygen into the body and carbon dioxide out of the body. It's also been shown to be directly related to the heart and its health, and also the gut and its health. Well, as we look at how we measure heart rate variability, this is where I realized it got incredibly complicated. It's not linear. It is described mathematically as a chaos model. Now, I'm no mathematician, so somewhere around here it started to lose me. We talk about evaluating that heart rate both in a spatial and a temporal sense. And these are fairly complicated. Spatial meaning on a beat-to-beat and size relationship. but temporal over time. And these can be linked, and depending on the equipment used, will give different results. We know that heart rate variability can increase or decrease with different diseases. So, for example, if someone has atrial fibrillation. A chaotically irregular, irregular rhythm. These people have increased heart rate variability and that's a bad sign for them and linked with increased mortality. But decreased heart rate variability could be a sign of some sort of autonomic nerve problem as well. Remember also that our medications are likely to impact this and how we interpret heart rate variability in individuals who have some sort of medication on board that would impact this system is anyone's guess. So I did look at trying to understand some of the metrics around heart rate variability and to be honest to try and describe them over a podcast for me. would be nearly impossible. Most of these require a bit of a table, and to be honest, I don't even understand the tables. So where does heart rate variability sit for me at the moment, and possibly for you? I suspect it's a measurement, it's an observation that we will start to use more and more, because what we will see is personal devices. smart phones and watches, for example, communicating and measuring that heart rate variability. What we're going to have to do is for each different sort of measurement, whether it's a prolonged measurement, a short measurement, whether we're looking at spatial variance, temporal variance, domain changes or frequency changes, all these are going to have to have a baseline assessment. to figure out what we're looking at and bring consistency to those measures so that we can compare apples with apples. I have no doubt that as time progresses we will get the chance to look at heart rate variability more and more. I think we will see the data sets coming out with individual devices helping guide our decision making around that. And I think as people wear these devices, wearable monitoring devices, we will see it come more and more into play. There's no question more data will come. But even down to something as simple as identifying when an individual may well be developing a cold, it could be that the heart rate variability is sensitive enough to start to change very early on in an infective process. I have no doubt that we will... see more and more about this i have no doubt that in the future i'll probably do another podcast on it probably when i understand it a bit better i'm almost sure that some of you out there at the moment who are listening will have apps that will have heart rate variability offered and they may well have their own algorithm that they've tested and because it's being reproduced through the same evaluation of the same components and characteristics can be meaningfully compared over time. But in the meantime, I'm going to suggest you look after yourself. Exercise. Keep an eye on that heartbeat. Eat a healthy diet. And I really do thank you for tuning in and listening to my podcasts. as that's a way that you will also keep educated, keep informed and therefore get the best health care. For now, I am going to wish you the very best. I hope you live as well as possible for as long as possible. Take care and bye for now. Did you know that coronary artery disease kills one in four people? So most of us are likely to carry some risk or know someone who does. If you're interested in finding out more about how to evaluate that risk, check out www.virtualheartcheck.com.au. It'll give you information about risk and what else can be done to be even more precise.
