What the Discovery of Blood Flow Can Teach As About Science Itself w/ Dr. Dhun Sethna | Crooked Media
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July 12, 2022
America Dissected
What the Discovery of Blood Flow Can Teach As About Science Itself w/ Dr. Dhun Sethna

In This Episode

For most of human history, people believed that blood flow was a one-way thing. The discovery that blood flowed two ways–that there was a circulatory system–didn’t happen until the mid-1600s. And it took more than a century for that discovery to be formally adopted by most scientific institutions. Abdul goes back in history to help us understand the resistance to science in the present. He interviews Dr. Dhun Sethna, a cardiac anesthesiologist and author of “The Wine Dark Sea Within” about the discovery of the human circulatory system and it’s implications for our time.




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Dr. Abdul El-Sayed, narrating: New Omicron sub-variant BA.5 shows an unparalleled ability to re-infect the previously infected. Pfizer and BioNtech announced a new trial for a, quote, “universal COVID vaccine.” Congress’s new reform bill has made the single biggest expansion in mental health care in U.S. history. This is America Dissected. I’m your host, Dr. Abdul El-Sayed. You hear the term “gaslighting” all the time these days. The term itself, gaslight, comes from a 1938 play by the same name. In the play, adapted for the big screen in 1944, a husband manipulates his wife by lighting and putting out a gaslight to make her question her own sanity so he can have her committed and steal her inheritance. Most of the time, though, people talk about gaslighting when there’s a fundamental miscommunication of emotions. People feel gaslit when somebody doesn’t fully embrace their experience. But gaslighting by institutions, where they systematically work to alter your perception of reality, that’s happening all the time. When GOP politicians or gun rights activists tell us that the problem with gun violence is actually doors, or our failure to arm teachers or mental health, that’s gaslighting. When the Supreme Court tells us that they’re taking away people’s fundamental rights over their uteruses in order to return the issue of abortion to the people, that’s gaslighting. When they tell us that a, quote, “originalist understanding” of the Constitution justifies unfettered access to automatic assault weapons when the framers of the Constitution only ever used muskets, that’s gaslighting. But I digress. Today, I want to talk about how gaslighting has shaped science, and why it still can happen today. We’re taught to understand science as received wisdom, as a sort of fundamental truths handed down to us by the ancients. That’s because most of what we learn is what we call quote unquote, “settled science”, meaning that there’s a pretty strong consensus among scientists that we’ve come to understand the fundamentals here. The problem, though, is that science is fundamentally about unsettling what we think we know. There is no received wisdom. Everything is open for question. And that’s how science is meant to progress. We ask questions about how the world works, and then we design experiments to test those hypotheses with the goal of proving them wrong. If the experiment does prove them wrong, we adjust our hypotheses. If it doesn’t, we take the given hypothesis as the best available explanation for how something works. That is, for now. But humans are not rational. We have feelings about things. We get comfortable with the status quo. There’s ego and reputation involved, and some of us have vested interests in the world working the way we think it does. Today’s experts, the ones who pose the hypotheses that are best supported, they’re the ones with the most to lose if these hypotheses get disproven, which means that they’re the ones most resistant to disproving them. They can use their power and their influence to push back against new hypotheses, to discredit the evidence supporting them, to discredit the people who propose them. And that’s gaslighting too. And it too often pits scientists against science itself. Today, I want to bring you a story from the history of science that captures how that can work. The “Wine Dark Sea Within” is a new book by Dr. Dhun Sethna, who traces the discovery of human circulation. It’s nearly impossible to overstate how important this discovery is. Heart attacks are the single deadliest disease in the U.S. and the world, and they’re fundamentally a problem of circulation, whether or not blood gets to where it’s supposed to, to feed your heart. Strokes, same thing, but in the brain. But it took 150 years for the scientific establishment to accept nearly indisputable science. 150 years. This was back in the mid 1600s. Of course we’ve come a long way since then, but it happened again 200 years later with Ignaz Semmelweis, a Hungarian physician who was driven out of medicine for arguing that doctors should wash their hands before they delivered live babies. Remember, doctors didn’t wear gloves back then. And it happened again to John Snow, the man credited with founding epidemiology itself, when he tried to explain that a London street pump was the source of the city’s cholera epidemic. See, while we think of the absurd things people believed in the mid-1600s or mid-1800s as crazy and backward, the people living in that time thought of themselves as cutting edge and progressive, just like we think of ourselves. Imagine what our progeny will think of us 200 years from now. And it’s that humility, the ability to recognize that we’re not living at the end of history, that matters most. We’ve just come through a pandemic that showed us just how little so many of our country-people think of science. We’ve watched the Supreme Court gut an evidence-driven definition of fetal viability for an unsubstantiated argument that life begins when a sperm and an egg meet, and robbed millions of basic bodily autonomy in the process. Scientific ignorance, gaslighting, is alive and well. And sometimes to see it play out in our own time. It’s worth looking at how it played out in the past. Here’s my conversation with Dr. Dhun Sethna.


Dr. Abdul El-Sayed: Can you introduce yourself for the tape?


Dr. Dhun Sethna: Yeah, sure. My name is Dhun Sethna, and I’m a clinical and academic cardiologist. And for 15 years I’ve also done cardiac anesthesia, which is giving anesthesia for open-heart surgery. And currently, I’m at the Carilion Clinic in Virginia, which is affiliated with Virginia Tech.


Dr. Abdul El-Sayed, narrating: Doctor Sethna’s new book, “The Wine Dark Sea Within”, is one of those books of history that helps explain our present. His sharp explanations of our understanding of blood from the ancients to the present, captures a lot about what makes science so hard. Not just the work itself, but the explanation of the work to people who are resistant to it because they’re bought into the status quo.


Dr. Abdul El-Sayed: The book was a really fascinating insight into the, you know, the history of science around a part of our physiology that is fundamental, critical to who we are, how we operate. Why did you decide to write this book?


Dr. Dhun Sethna: Well, I’ve always been interested in the history of cardiology, and this is my first venture in nonacademic publishing. And I decided to select a topic which would make a good story, you know, have a beginning and an end, and at the same time would be a topic that will be of significance in our understanding of the heart, as we understand it today, and also have an impact in modern medicine. And one such topic is the discovery of the circulation of the blood, which was done by William Harvey in 1628.


Dr. Abdul El-Sayed: And the story that you tell is really quite fascinating, right, because blood is one of the most obvious things about the human existence inside of us, right? So if you see a person, it’s not immediately clear that that they’ve got blood coursing through their veins until, of course, they get cut or they get injured. And, you know, the most common injury that anybody sustains from the time you’re young is, you know, you fall, you skin your knee, you start bleeding, which opens up a really interesting set of perspectives on what this substance is and what it means for us. And that’s the story you tell, I think, brilliantly in the book. Just for our listeners. I think it’s helpful to understand some of the context, some of the physiology here. So what is blood and why is it so fundamentally absolutely critical to us?


Dr. Dhun Sethna: Yes. Well, let me begin with an observation that I guess even the first human being must notice, and that is that when you cut yourself, as in an injury, and you bleed, that you can bleed quite profusely, and when people bleed quite profusely, they die. So the first observation is that blood is something vital for life. Blood as traditionally is a, its function is to transport nutrition and oxygen to the tissues, and carry the waste back again for elimination through the lungs and through the kidney and the liver and the gut. Now, that’s the traditional idea about what blood does, but today we actually think of blood as an organ system, because it contains and carries also a lot of hormones, enzymes, and vital chemicals that are critical for the function of the body. So it is really an organ system. And equally relevant, and that sort of brings us to the book itself, is that these constituents of the blood have to be transported to the tissues, and and, so the story of the book is, how does this transportation occur? What is the flow of the blood? And how did it evolve into our current thinking that the blood actually circulates–moves in a circle–from the heart to the periphery and back to the heart?


Dr. Abdul El-Sayed: You know what’s fascinating, right, is that the easy metaphor I always find for this is that we all know the value of roads and bridges, right? I mean, there’s a whole political discourse about do we rebuild our infrastructure? And that always means roads and bridges, because if you don’t have them, you can’t move around. And in some respects, the blood is that infrastructure for the body. It is the roads and bridges that take you from, you know, the parts of the body that tend to get more of the attention–the organs, the buildings–but if you can’t if you can’t get between them, it doesn’t quite matter. And, you know, you mentioned they’re about excretion, and people don’t usually think of their lungs as a excretion mechanism. There are, you know, obviously two other ones that we think about a lot more, but, you know, every time we breathe out, there’s something coming out and folks don’t really quite appreciate it. We breathe in the oxygen. We breathe out the carbon dioxide, just as, you know, our liver and our gut systems and then our kidneys work on excreting, you know, other compounds that are produced in the day-to-day of our activity. And then the other part of it that’s really fascinating is that it’s not just that blood is is infrastructure. It’s also that blood is self-correcting infrastructure, right? It’s got the means of its own corruption inside of it. And there’s really, really tight chemistry inside that always was really fascinating to me, let alone being the, you know, the main bulwark of your immune system. I want to ask you, you know, just so folks get the sense of, how does blood move, like what is the circulatory pathway? How should we think about, you know, arteries and veins vis-a-vis the heart, vis-a-vis the the peripheral organs that are constantly getting perfused by blood?


Dr. Dhun Sethna: Well, that’s a good question. And I think it’s a great introduction to sort of briefly cover the history of how blood flows. The title of my book is “The Wine Dark Sea Within”, and that’s a strange title, but it’s the phrase “The Wine Dark Sea” that’s taken straight out of Homer’s poem about the Trojan War, where he calls the Aegean Sea the “Wine Dark Sea.” Now, the Greeks did think about a life giving fluid within the blood–I mean, within the body. And I guess standing on the shore and watching Homer’s wine dark sea ebb and flow in the tides, they extended that analogy to the body. And really, the first theory of blood flow is just that, and that is that there is a life-giving fluid within the body that ebbs and flows like the tides. It flows from the heart to the periphery and then back again in the same blood vessel. And as an extension, they said that air also flows in the same way. So you have air actually pushing the blood back in flow. And that became the standard model for physiology–the ebb and flow of blood–for 15 centuries until the time of Harvey. And there were just a few variations added on to this basic concept. I think the first one was that you mentioned roads and bridges–well, the what I would like to introduce here is an irrigation system. The Greeks thought of the blood flow as an irrigation system where nutrition is made by the liver, which was the concept in real time from the food and drink that is taken in. And in real time, it flows from the veins, from the liver, through the veins to the periphery, where in real time it is consumed completely. Because that’s what happens in an irrigation system. The water flows through the canal, it goes through the crops and is taken up by the crops. Now that idea is significant because it’s a one-way system and there is no need for anything to return. You see? So there is no need for the second part of this circulation to exist. And that was the reason why it took 1,500 years for such a system to be overcome. And Harvey was the first person who did that.


Dr. Abdul El-Sayed: So just to clarify, so the mechanism that folks thought was that, you know, there is almost like the, if you think about the sea, you have the air movement and then you have the water movement underneath, right?


Dr. Dhun Sethna: Yes, yes.


Dr. Abdul El-Sayed: There’s always the air that glides a sailboat across the sea. And so in breathing, right, which was the thing that people saw, the assumption was that we were moving air to move blood, and that there was a one-way flow from our liver into the end organs. But there wasn’t really much given to the question of the issue of excretion. I want to ask you, how does this relate to the idea of the four humors, that folks might have heard of? So blood was one of the humors. What were the others? And how do we think about the way that ancient Greeks sort of put this system together?


Dr. Dhun Sethna: Well, I touched upon that briefly earlier. You know, we said that blood was an organ system and it had, it carried hormones and enzymes and other vital chemicals which are useful for the function of the organism. What we call hormones and enzymes, they called humors, and they basically thought about humors with full properties: hot and cold, wet and dry. And if all the humors were in equilibrium, then the body was in a state of health. And if one humor gained predominance, then that’s what caused disease. So it’s the same concept, but they use this terminology of the four humors, and that actually was the pathophysiology, the way in which diseases occur, and formed that thesis for 1500 years.


Dr. Abdul El-Sayed: I want to ask also one of the well-known blood-related treatments that anyone who’s even had a sort of a casual understanding of ancient clinical science will know is bloodletting, right? Whether that was done by literally just bleeding someone, or done, you know, even more intensely by having another living being suck blood out of someone. How did bloodletting figure into their understanding, their theory, about how what blood was? Because you can imagine, right, if you know that if you bleed enough, you’re going to die, the idea of bloodletting seems to be somewhat orthogonal at best, if not entirely counterproductive to trying to make someone healthier.


Dr. Dhun Sethna: Yeah. Yeah, that’s true. And that goes back to another aspect of the theory of disease. You know, one of them was the four humors, and the way to get about that was that if they felt that it was a cold humor that was predominating, then you focused on countering that with hot stuff–what they called, you know, foods that gave more heat and thereby, you know, opposed the cold humor. The other aspect of disease was spirits–evil spirits, evil substances, dangerous substances–that were inhaled or ingested or somehow got into the bloodstream, and they attacked a particular organ and caused disease. So the natural theory, the natural treatment for that was to just get that humor, that evil substance, out of the body. And you could do it in two ways. You could do it by ingesting really nasty substances–it’s actually the philosophy that you set a thief to catch a thief. So if you have a noxious agent circulating–not circulating–a noxious agent accumulating in one tissue, then the best way to get rid of it is to fill the body with even more noxious substances. So you have, even to the extent of having excretions forming part of your therapy so that if you take in nasty stuff, maybe you’ll drive out that malignant agent from the body. A more direct approach, of course, is to bleed the blood vessel that is attached to that organ. So if, for example, you had a disorder in the left side of the chest, pain in the left side of the chest, they believed that the left side was associated with the spleen, and so if you–and they believe that the main artery at the left elbow was the splenic artery–so if you cut that artery and bleed from that artery, you’ll get all the malignant agents in the spleen related to the chest pain on the left side of the body would come out. So really, you drained out the evil spirits and, uh, and hoped that, you know, that would lead to partial recovery. Of course, the danger was that you could over bleed and kill the patient. An interesting anecdote, actually, is that of George Washington, when Washington died, he actually died from bleeding. You know, his original symptoms was just the common flu. He had a cough and a cold so his physician started to bleed him, and by repeated small bleeds, you know, they actually pretty much exsanguinated him, and he passed away. And after he passed away, the physicians wanted to actually open up his trachea and try to do respiration, and it was his daughter who prevented that. So George Washington is an example of recurrent bleeding carried out in the spirit of well-being and healing that eventually killed him.


Dr. Abdul El-Sayed: Wow.


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Dr. Abdul El-Sayed:  I want to ask you now, so our common understanding comes from Harvey. How did Harvey discover and work out the current circulatory system as we know it to exist today?


Dr. Dhun Sethna: Well, good question. The answer is that he did it two ways. The first thing was that just around that time it was published that the veins had valves in them. Now these valves are little doors– they open and shut, but they open and shut in such a way that the blood flow can only go in one way, in one direction. And that direction is from the periphery to the heart. Now, if you think about that, that’s totally contrary to the contemporary thinking of Galen’s system, where blood is made in the liver and that’s the center, and then goes in the veins to the periphery, so the blood goes from the center to the periphery. And yet the valves in the veins suggested that the blood flows in the opposite direction. Now, Galen’s was a hypothesis. What Harvey could see with his own eyes was a reality. And that reality of the veins was a duplicate, it was reproducible, no matter which veins you opened in which animal, the valves all worked in the same way. So this told you that something wasn’t right. I think what clinched the deal, so to say, was that he, for the first time thought about physiology in quantitative terms. He was one of the first individuals to introduce quantitation in medical thinking. And here’s how he came about. He had at autopsy a human heart. And so he opened the left chamber of the heart and filled it with fluid. And every time he found that, the heart filled up with about two ounces. So what that meant was that if the heart contracted, about two ounces of blood would come out with each contraction. And so if the heart were to contract, so the amount that would be pumped out per minute would be two ounces into a 72 times, which is the heartbeat. So it would be two in 72, which comes to about 144 ounces per minute. And if you multiply that by 60, you come to a number, which is 8,640 ounces of blood being pumped out every hour. Now, that’s a tremendous amount, because if you can put the ounces into pounds, which he did, it comes to 540 pounds. So according to their modern theory, which was Galen’s theory, 540 pounds of blood are produced in real time every hour by the liver, and then is consumed by the tissues in real time every hour. And remember that blood comes from the food and drink that is taken in, and it’s impossible for anyone to take in 540 pounds of food and drink every hour. So clearly there was a, an illogic phenomenon right there.


Dr. Abdul El-Sayed: So just to sort of break that down, there are really two pieces, right? It was the recognition that blood couldn’t just be moving one way if there were back-way valves, right? That was part of it. And the second part of it was if the heart’s moving 540 pounds of blood every hour and it’s going from one place to another inside the body, then the only way that that would be possible is if we were both eating and excreting 540 pounds worth of mass every single hour. So the only way to explain it is that this blood has to be coming back, right?


Dr. Dhun Sethna: Exactly.


Dr. Abdul El-Sayed: And that’s the only, that’s the only set of explanations. That’s really quite fascinating.


Dr. Dhun Sethna: Yeah. Yeah. That’s basically the, and remember, you know, that blood, the vascular tree, was considered an irrigation system, and these numbers made that impossible. So putting the two together–the impossibility of Galen’s hypothesis and the reality of veins and the valves–putting those two together, he figured out that, you know, blood has to be going from the arteries into the veins. He also did a few ligature experiments where he tied a ligature on the arm–actually, he also did it in fish, where he looked at the aorta and the vena cava, which are the two big vessels in the center of the belly, and when he when he put a ligature or tied a ligature on the artery, he found that the part of the aorta that was distal, away, from the ligature, just collapsed. And the blood started accumulating before the ligature, suggesting that blood flowed in the artery only in one direction–from the heart to the ligature. When he did the same with the vein, the reverse happened. The veins started filling up and bulging distal to the ligature, and that part of the vein that was going to the heart collapsed. Not only did the vein collapse, but the heart itself collapsed, you know, became empty. And when he removed that ligature, everything filled up again, suggesting again that in the vein, the blood is going from the periphery to the center, and in the artery, from the center to the periphery. So putting it all together, circulation was inevitable.


Dr. Abdul El-Sayed: So just for folks who are listening, ligature is basically a bypass. So if you can bypass a piece of the artery, it’ll tell you where blood is moving. And so what he did was he contrasted what happened when you bypassed a part of the artery, and when you bypass part of the vein. And just for context, you know, our current, we think of veins as being what’s running through our body, which is quite similar to what Galen was thinking. But we actually have arteries and veins. Arteries are what carries from the heart to your periphery, to your muscles and your organs. And then veins are what carry from your organs back to the heart. And they’re actually really, really different. Arteries are really, really thick, and they’re intended to sustain all of that pressure coming out of the heart. Whereas veins actually have to have those valves because the pressure is so small. A lot of that pressure gets dissipated in the peripheries because the surface area is so much bigger, that the veins actually have to have those valves that Harvey discovered to keep blood from flowing backwards. Otherwise it would all pool in our organs. And so by being able to piece all of those pieces together–what happens when you bypass arteries versus veins, why is it that veins have to have these one-way valves, what happens when, you know, you don’t fill the heart back up with blood–he was able to piece this together. Now, Dr. Sethna, when he did all these experiments, it’s not like people’s minds changed immediately, despite the how strong his evidence was. How long did it take for this understanding of the circulatory system to be adopted?


Dr. Dhun Sethna: Well, it took another 150 years–


Dr. Abdul El-Sayed: Wow.


Dr. Dhun Sethna: –for that. And the reason is very simple. It’s well, it’s the tyranny of ideas. You know, old ideas die hard. And in those days, the most powerful folk in medicine were the academics and the professors. And remember, the professors had made their careers, they had written books, they were teaching Galen’s physiology. And if Harvey was, in fact, was to become the dominant physiology, even if it was true, it meant that the tenure and the positions of the professors was at great risk. Their very livelihood was at great risk. So it was necessary for them to keep Galen in power, and tried their best to oppose Harvey. A secondary interesting background is that Harvey’s century was a century of religious strife. The 30 Years’ War was going on. Harvey was an Anglican–a lot of Europe was Catholic–and that also contributed because if you look at it, most of Harvey’s opponents were Catholics. So it was a combination of things that happened today in real life, that put together led to the opposition to Harvey.


Dr. Abdul El-Sayed: You know, given the anecdote that you shared earlier about the the way that George Washington died, you could imagine that if there wasn’t such huge opposition to Harvey’s discovery, given that it was in the mid-1600s, that didn’t really, this didn’t really become accepted until 1800. And George Washington’s entire life was in that period when we knew, right, there was enough knowledge out there in the world to have changed the course of his treatment, but that it wasn’t, it wasn’t followed, and there was a resistance to following it. I want to ask you in just a second about the medical implications, but what does this tell us about the way science moves more generally? You know, do you feel like we’ve gotten better as a society at being able to accept these massive changes in paradigm? Or do you feel like we are still in a place where, like you said, old ideas die hard, and how much further do you feel like we have to go?


Dr. Dhun Sethna: Well, I’ll answer that by giving you two examples. In the 1800s as, well, now is well known, Darwin’s theory of evolution was very controversial, and it is still controversial even today. You know, where in schools today, for example, evolution is not taught, is not taught at all, you know, because it contradicts Genesis. Let’s go to the 20th century. What about Einstein’s theory of relativity, and the whole concept of quantum physics? That wasn’t accepted right away. That took some time–maybe over the next 25, 30 years–to become maybe the greatest discovery in in physics of all time. So that continues, you know, and it is likely to continue. It was there in the last century. It was there in the century before that, and it’s going to be in our present century also.


Dr. Abdul El-Sayed: Yeah. You think about Semmelweis and the germ theory of disease, and the fact that, you know, he had demonstrated that the practices that were commonplace were literally killing people in childbirth, and he was driven out of medicine for it. You know, what’s interesting about this is that every moment in history feels like the end of history. Every moment says that we’ve discovered all there is to discover, we now understand how things work, and look at how far we’ve come–and the danger, of course, is that the more you learn, the more it justifies that there can’t possibly be more to learn out there. And science tends not to move as linearly as we think it does. It tends to move in fits and starts, and it tends to move sometimes by major paradigmatic shifts and changes in what we thought we understood. Now, of course, we have a lot more tools, and the scientific process itself has as come to be understood, so, you know, people are looking for these paradigm shifts a lot faster. But there is a way in which, you know, our minds tend to be ossified to what we see as normal. And so, you know, while it fuels from where we sit, looking back at Galen, or looking back at Aristotle, or looking back to the Greeks before that, that they were so in the dark, and how could they possibly believe what they believe, it’s likely that in 100 years people will look at what we’ve been doing and what we’re doing and say, Well, how could they possibly believe that? And there’s a certain humility to appreciating it, which is part of why I’m so excited to share your story here, because I think it’s an important mechanism for understanding how science moves and how sometimes people in the present who are best situated to benefit from changes in science, will not just ignore that science, but actually push against, and push back against, that science because it implicates their own misunderstanding. When it comes to Harvey, so much of medicine is predicated on understanding how blood moves–everything from a heart attack to a stroke–all of those things are about the movement of blood or the failure of movement of blood to different parts of our bodies. How should we understand the clinical implications of Harvey’s discovery today, and what are some of the things that we take for granted today that only were possible because of him?


Dr. Dhun Sethna: Well, you actually touched on that, one of those right now, and that is that if a blood flow is required for maintaining health, then a inference from there would be that a lack of blood flow or an insufficiency of blood flow to an organ could well lead to disease. And that idea has been validated now, that in fact, heart attacks and strokes both occur because of an insufficiency of blood to the organ because there are blockages or clogging up of the arteries going to those organs. The other big change, let’s say, would be in therapeutics. We get a, what the circulation means is that if something is introduced at one site directly into the blood, it goes to each and every site, each and every cell, in the body automatically, because the blood circulates. And what that means is that before Harvey’s discovery, what we now take as commonplace as giving medicines intravenously, like chemotherapy, antibiotic therapy, transfusions, would be unheard of. Insulin shots where we give insulin below the skin and it goes to all parts of the body, to each and every cell, happens because of the circulation. Even something like a nasal spray that you take for allergy, you spray in the nose, and yet the effect occurs, you know, say in the lungs, if you have chronic lung disease. All that happens because of Harvey’s circulation. And we don’t even think about the circulation. It’s so routine in our lives. Let’s think about interventions. I mean, you know, something like a heart catheterization, it’s almost normal today. I mean, everyone knows someone who’s had a heart catheterization. Everyone knows someone who’s had a stent put in in some artery, and all that–who’s had a pacemaker electrode put in–all that occurs only because blood flows in one direction in the arteries and it flows in reverse direction in the veins. Because you need that–to use a big word–you need that uni-directional flow to float the electrodes, to introduce the catheter so that they float directly into the bloodstream where you want it to go, to the site to where you want to put the stent. So all that we take for granted. Now, a third idea that I want to introduce is that, you know, we think of the circulation, we’ve thought of the circulation so far as blood going in a circle inside the body. What about blood going in a circle outside the body–what is called extracorporeal circulation? Where does that come in? And that comes in interventions like dialysis. Dialysis is nothing else but the circulation of the blood outside the body. The heart-lung machine–chronic kidney disease–the heart lung machine, you know, which is used for open heart surgery–and everyone, you know, know someone who’s had bypass surgery–the heart-lung machine, as the phrase implies, is blood going outside the body into a lung, artificial lung, which is a membrane oxygenator, to use the technical term. And then it goes into an artificial heart, and then it goes back into the body. So you actually have a circulation coming out from the artery, going through the artificial lung, the artificial heart, and then going back into the body. And that concept could only occur if you originally had the concept of a circulation which is intra-corporeal, or within the body. Even the artificial heart is nothing else but is circulation going through a device and then entering back into your own body, thus sparing in two ways. Firstly, it could be a permanent structure where you just live life-long on the artificial heart. Or it could be a bridging device where you ease the strain off your original heart, allow the heart to recover, and then you can disconnect the person from the artificial heart and let his own heart take over. I mean, all these mind-boggling concepts that nowadays we take for granted would be impossible without the discovery of the circulation, which is why it has been called the greatest discovery in medicine: the circulation of the blood.


Dr. Abdul El-Sayed: We really appreciate you taking the time today to talk us through the way blood moves, and how we learned about that, and what it means for our understanding, both of ourselves, but also of the way that science moves and shapes society, and our ability to heal ourselves. That was Dr. Dhun Sethna. He’s the author of “The Wine Dark Sea Within.” I highly recommend the book. I hope you’ll check it out. And we really appreciate you joining us today.


Dr. Dhun Sethna: Well, thank you, Abdul. My pleasure.


Dr. Abdul El-Sayed, narrating: As usual, here’s what I’m watching right now. We’re learning a lot more about BA.5, the most transmissible of the sub-variant circulating right now, and the most transmissible sub-variant of COVID-19 we have yet to see. While we think about it as an Omicron sub-variant, a new paper in the journal Nature demonstrates just how far evolved it is. The distance between BA5 and BA.2.1.2, which is what was circulating just a couple of months ago, is the same as the distance between Delta and the original SARS-CoV-2. To put it in perspective, compared to BA.2 BA.2.1.2 was about 80% more resistant to three doses of vaccine. BA5 is four times more resistant. It signals the virus’s nearly unbridled ability to evolve, and that we could be dealing with COVID for some time to come. Indeed, right now, cases, though slowly, continue to climb. They’re up about 15% over the last two weeks. Hospitalizations and deaths are up, too. While we now have treatments that are highly effective, this virus is still a threat. Make no mistake about it. Toward that end, one of the challenges to these treatments has been getting them in people’s hands. The FDA has now authorized pharmacists to prescribe Paxlovid, which should facilitate getting them to recently-infected people faster. On the vaccines front, the speed with which the virus is evolving suggests that so long as we’re trying to key our vaccine into old variants, we’ll be 2 to 3 steps behind. Which is why a recent announcement from Pfizer and BioNtech that they’ve taken a new, quote unquote, “universal” COVID vaccine to trial, is welcome news. The hunt is for a universal vaccine, one that keys into an unchanging part of the virus rather than the spike protein the virus is able to switch out with relative ease. Pfizer and BioNtech’s version also focuses on T-cell immunity, which could be important to providing longer-term, less variant-specific protection against serious illness.


Last week, on July 4th, a 21-year old man armed with an assault-style rifle killed seven people and injured dozens more in the Chicago suburb of Highland Park, Illinois. It’s poignant that this should have happened on July 4th, because sadly what can be more American than a mass shooting? The shooting took place just ten days after President Biden signed the bipartisan Safer Communities Act into law, the nation’s first gun reform bill in over 30 years. What’s troubling, though, is that the law probably wouldn’t have stopped the shooting from happening. The shooter obtained his guns legally in Illinois, a state with one of the country’s strongest red flag laws. That, despite the fact that police had visited his home twice, and confiscated 16 knives, a dagger, and a sword on one of their visits. But that doesn’t mean that the bill won’t do some good in other ways. In fact, it’s the biggest expansion of mental health care in American history, and also the biggest expansion of Medicaid since Obamacare. And that funding will expand a system of certified community behavioral health clinics across the country. And regardless of the bunk pretext about guns and mental health, this is a big effing deal.


Dr. Abdul El-Sayed: That’s it for today. On your way out, don’t forget to rate and review the show. It goes a long way. And if you love my explainers at the top of the show, check out my YouTube channel, YouTube.com /abdulelsayed. No dash. Also, if you love the show and want to rep, hope you’ll drop by the Crooked store for some American Dissected merch. We’ve got our logo mugs and T-shirts, our Science Always Wins sweatshirts and dad &D caps are available on sale, and are Safe and Effective tees are on sale for $20 off while supplies last. America Dissected is a product of Crooked Media. Our producer is Austin Fisher. Our associate producer is Tara Terpstra. Veronica Simonetti mixes and masters the show. Production support from Ari Schwartz, Inez Maza, and Ella Price. The theme song is about Taka Yasuzawa and Alex Sugiura. Our executive producers are Sara Geismer, Sandy Girard, Michael Martinez, and me, Dr. Abdul El-Sayed, your host. Thanks for listening.