1.1 Macroscopic Perspectives of HRV

• So the title of my talk is meta perspective and heart rate variability is heart rate variability, antiquated or indispensable. And this is my quick disclosure slide. And the reason I titled the talk this way was to highlight the differences in views towards heart rate variability, the views that are often divided along occupational disciplinary lines. 
• So if you ask a clinician in healthcare setting, the, the response you get is that heart rate variability is antiquated. On the other hand, if you ask an athlete or a silicon entrepreneurs seeking to optimize physical or cognitive performance, they may say that heart rate variability is really important and indispensable. 
• Personally, as a clinician and a researcher wearable devices, I find this divide really fascinating. And I'm also acutely aware that divide is larger than many will recognize, because many physicians are simply not aware that the heart rate variability is widely espoused as a marker of health and performance. 
• While many athletes have little idea how skeptical the medical community may be towards heart rate variability. The other day, I was listening to a podcast on heart rate variability, and one of the speakers was saying that heart rate variability is sort of commonly used in the clinical setting for diagnostic and prognostic purposes. And I have to say that's really not the case. 
• And to show that to illustrate this, in the hospital, we utilize something called the Zeo patch. It's an FDA approved heartrate monitor which can you can keep on for up to 14 days. And when someone gets admitted to the hospital for syncope, which is loss of consciousness, chest pain or palpitations, we send people home with this XYL patch. And when you get the actual medical report, this is the actual medical report actually is a sample of someone, you can see that they present a lot of the information such as heart rates, events, which include arrhythmias, such as ventricular tachycardia, atrial fibrillation, sinus pauses, and various activities. 
• But nowhere in there is there anything about heart rate variability. And you would think that with something like this device, which is a perfect instrument for heart rate variability, that that would be included in this, but simply, it's not included because its heart rate variability is not used in the clinical setting. 
• Last time, any medical professional society had put up a major position, or consensus paper heart rate variability was in 1996. It was a joint statement put out by the European Society of Cardiology, and the North American Society of pacing, electrophysiology, and published in the two big journals, European Heart Journal, and the circulation journal.
• And it sort of quickly went over, reviewed some of the literature and provided some guidelines, they talked a little bit about the methodology of heart rate variability, included time and frequency domain analysis, short term versus long term acquisition of heart rates, data and some of the reporting requirements such as the ECG signal, the duration, the pre processing that you needed of the signals. 
• They also talked about the physiological correlates, including autonomic influences, the frequency components, and then some of the clinical applications actually, they only identify to post myocardial infarction. So you can obtain Heart Rate Variability one week after an acute MI, and that information was found useful to determine whether someone was at risk of arrhythmia or death. And then the diagnosis of diabetic neuropathy. Now, this was highly cited, but again, this was in 1996.
• The only follow-up of this paper was done in 2015. And it talked largely about nonlinear methodologies, which I will be talking on this talk it would be in subsequent talks for this series. And this basically the same group, the European Society of Cardiology, and another European Heart Rhythm Association reviewed a number of heart rate variability, nonlinear methodologies publications out of 800 plus, and found that 21 studies met quality criteria. 
• And then these are sort of the various methods that were evaluated, including gait tangent frequency analysis, point carding, deceleration capacity, acceleration, capacity, entropy, I'm not gonna go into too much details, but their recommendations was ultimately that traditional measures which were discussed in the prior guidelines in 1996, was the remains the method of choice and widespread use of nonlinear methods was not recommended. 
• So this was the most recent update that was given by any sort of large medical professional society and it was published in a much smaller journal called Euro pace. And it really didn't get much citations. So, you know, clearly, the importance of heart rate variability in medical establishment is in question. And so it hasn't been widely utilized. Contrast this with how wearable companies use heart rate variability, and often considered as a cornerstone for the app functionality. 
• So what is a well-known company that has its own device and its app, and they have a metric called what recovery. And one of the cornerstone of this measurement of recovery is heart rate variability, and in addition to resting heart rate, sleep and respiratory rate. And this enthusiasm towards heart rate variability is not limited to wherefore world. In fact, heart rate variability has garnered a steady rise in interest in the actual peer reviewed sciences. 
• And if you do a literature search on the number of Heart Rate Variability related publications, you will find that there has been a significant increase over the past three decades, even more so than you would anticipate based on the rise of number of journals and the growth of science alone. 
• So where does the truth exist? And why is there such a contrast and enthusiasm here. And some of the handsets to why this growth has occurred in maybe how some of this disparities and this differences in this perspective or variability has arisen from is to sit, you can take a look at the number of publications by discipline. 
• And so what I did here was I took the number of publications divided willing to discipline by decades, into 19 9070s, you have 157, total publications 1984 to 6090 97,000 2000s, about 1500 15,000, Ira variables in 2010, about 28,000. And then just in the 2020s, alone, which is just 2020 and 2021. 
• Already, we have nearly 5000 publications. And if you take a look a little bit of the patterns of this heart rate variability publications, you can notice that in the beginning, the 1970s and 1980s of structures and gynecology was the leading discipline that published in heart rate variability and why is that was because fetal heart rate monitoring was sort of became popular, and now this becomes a standard practice. And you could see that obstruct your gynecologist no longer so the omnic discipline that publishes in heart rate variability, then came the cardiac and cardiovascular fields. 
• And in the 1990s, and 2000s, they essentially dominated in publications in heart rate variability, and that the domination slowly sort of withered away, and then they lost their lead in 2020. 
• And if you take a look at the neurosciences, you can see that in the beginning there, you know, continue to be present throughout the decades. But in the beginning, in the first three decades or so a lot of the focus was on sort of autonomic nervous conditions, such as diabetic neuropathy, through the reiterations of transplanted farts, and some other autonomic nervous conditions. 
• But then later in the 2010s, and 2020s. The reason it really sort of gained prominence was because of the development of neuro imaging and neuro technologies in the recent decades. And then you can see that engineering and biomedical came into view and the 20 cats and 2020s and in Sport Science also became significantly important.
• So the goals of this talk is to appreciate how science of Heart Rate Variability has evolved over the past 50 years. Recognize the various ways heart rate variability is measured, to obtain a basic understanding of heart rate variability, physiology, and to understand how different perspectives of Heart Rate Variability has emerged.

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