Hi, I'm Eric Grostowski, and welcome to another session of EP on EP. I'm delighted to have with us today Dr. Mark Link, who is the Professor of Medicine at University of Texas Southwestern. Mark, welcome to the show. Thank you, Eric. Now, let me remind people of an event that occurred recently. DeMar Hamlin, on January 2nd, 2023, had a cardiac arrest after tackling a ballplayer on the field in a well-publicized game. And suddenly, the world is abuzz about this otherwise rather arcane condition that you've had a lot of experience with, commotio cortis. I think it's a great chance for somebody like you to explain to everyone a lot of the factors here. And could you start with just telling us, what is commotio cortis? Sure. And thanks so much for having me on the show. Commotio cortis is a condition of sudden cardiac death when an individual gets struck in the chest. And what we know causes it is ventricular fibrillation. We didn't know that until probably 20 years ago. We didn't know if it was heart block or, you know, BT or ischemia. And there's some crucial things that are important in the human condition. And that is, it tends to happen in adolescence. It's pretty rare happening over the age of 20. And I know DeMar was 24, and that's unusual, but not unheard of. And the individual gets struck in the left chest with a hard object. Now, typically that hard object is a baseball, a lacrosse ball, a hockey puck, cricket ball, but it can be a body part. It can be a fist, a shoulder, a knee. So they're struck in the left chest directly over the heart. And then they have about five seconds of lucidity before they collapse. And that's kind of universal around all the commotio movies that I have. And I have actually five movies of commotio. And when you think of it, it's because when you go into BF, you don't immediately lose consciousness. It's just like when you go into heart block. It's five to six seconds before you drop. So that's, you know, DeMar was a perfect example of commotio. Hit in the chest, stands up, looks dazed, and then collapses like a stone. That is a typical commotio event. The only thing not typical was his age. It's seen in People 24, but it's typically in the adolescents. That's a great description. I have a whole bunch of things I want to ask you about it, especially your research. But let's stick with this for a second because after it occurred, I'm sure you got deluged with calls. I had several people calling me and one of them was a former NFL coach who I know who said he had spoken to several of his colleagues and not one of them had any recollection of ever seeing any player go down like that ever in their careers to high school, college pros. And that's, you know, I know what you said is absolutely what everyone thinks. I mean, as far as, you know, it's consistent with. But with the padding and the adult age, what are your thoughts on that? I mean, I know that's consistent with do you think it's diagnostic of? Well, to make the diagnosis of commotio, you have to have that kind of collapse with a strike in the chest and a normal heart. That's part of the definition of commotio. You can't have hypertrophic cardiomyopathy, long QT, anything like that. So yeah, but his age is a little bit atypical, but everything else is completely typical of commotio. And as to the pads, we don't know exactly what kind of pads he was wearing, but we know that in the commotio cordis registry, there's probably about 30 incidences in football. So it's not unusual. In fact, football is the fourth most common sport it happens in. And in football, the pads that they wear sort of cover the top half of the heart. But then when you lift up your arms, it completely exposes your heart. That is not a pad that's meant to protect the heart. It's a pad that's meant to protect the shoulders. So very different than pads in baseball and lacrosse, which completely cover the heart. So in a patient like this, basically, if you do a complete workup and find nothing else, that's your default diagnosis then. That's correct. That's how it's defined. I got it. So maybe what we can do is actually go into your research and you can explain it to us. You did some really important studies back, I don't remember exactly when, the 90s maybe. Maybe you can explain to the audience what kind of studies you did and how you did them and what your results were. Sure, sure. So in 1995 was this seminal article published in the New England Journal by Barry Maron on commodial quarters, describing 25 human deaths and they all died. And my boss, Mark Estes, wrote the editorial. And Barry Maron called up Mark Estes and said, hey, don't you have a fellow that would like to look into this and see why this happens? And so Mark turned to me and said, do you want to do this? And I said, hey, that sounds kind of fun. So that's where the start is. I wrote a $40,000 grant to NACCHI and they funded me. And so I had to come up with some sort of way to have a mechanism hitting the chest. And I started by, I figured out the timing right away. I used a commercial EP stimulator that was attached to a surface EKG. And so I could alter the time and this stimulator, I had to amplify the signal and then it went to a solenoid that you could open a clip. And I started by dropping heavy weights from the ceiling. That didn't work at all. So then I had to build something that could throw a baseball. So I did that in my basement. And as you can imagine, the amount of force to throw a baseball at 40 miles an hour, it's a lot of force. And it's not so hard to generate that force. It's hard to stop it. So I ended up splintering a dozen PVC pipes before I realized PVC couldn't do it. And so I came up, I had a compound bow was my power source, because a compound bow creates a lot of energy. And in the end, I used it like a catapult and it just shattered those PVC pipes. So in the end, what I did was mount the ball on an arrow and that's what worked. And then I had a trigger at the, you know, you pull it back, cock it and you had a trigger that could release it. So you could time, I could time it within five milliseconds of where I wanted it. It needs to go directly over the heart. We put the animal anesthetized completely out in a sling with their feet down to approximate the human condition. And then in the first animals, we scanned through the QRS, through this ST, through the downslope or G-wave. And what we found is that when you impact intonate 20 to 40 millisecond window prior to the peak of the G-wave, we got BF. And boy, we were really surprised with the first time we got it, but it was, it was amazing. And it was very reproducible. If we controlled for all the variables, we could get BF 50% of the time. So I'm going to show the audience, I'm going to hold something up. I hope they can see it. This is an article that I think if you have interest in this area, you should all read. It's a paper I pulled from my files. You can see by Dr. Link and it was in Circulation Arrhythmias in 2012. So since you've described that, let me show the audience. This is one of your examples, right? Correct. I think that's peak number seven. Let's see if we check your memory here. I can't find it off the top of my head, but I'll believe you. And this is a wonderful picture that I think really goes to show, I hope that's seen by the audience, that sort of the mechanism. And maybe while I'm holding this up, that's that vulnerable period on the T-wave there, right? With that little blue. Right. We heard it from Shock on T when we used to do DFT testing, but the Shock on T window is wider. It's probably 40 milliseconds wide, whereas our window is really 20 milliseconds. And I saw that. Well, I was going to ask you about that because when I read your paper, now when I first looked at it, I really wasn't looking at the Shock on T stuff we did in the lab when we used to test DFTs, but I rethought it and it looked like the Shock on T that we used in the lab was a little later on the T-wave than at least some of the figures. But I don't know if that's just because when you throw something against the chest, I mean, you can't time it actually to the millisecond, right? So is there a difference there? Yeah. We never crossed. We never were positive from the T-wave peak. Whereas with Shock on T, you can go about plus 10, plus 15 and still ... Yeah, that's what I think. Right. Ours are all pre-T-wave peak. Last thing, which is just a general comment, and I know you've been active in this area. What's your recommendation about AEDs? I mean, we've gone through a whole bunch over the years. Obviously, they should be there, but should they be there for every sporting event, do you think? Have we gotten to the point where that's just something that should be there anytime there's a sporting event going on that's ... I don't mean like kids pick up ball on the ground, but I mean an official sporting event. Do you think that that should be sort of mandated? I think if you're going to have a crowd there, it should be mandated. You're more likely to have a father or a mother have cardiac arrest than you are a kid on the playing field, but it's not so bad to save a father or a mother. Very well put. Really strongly about is all high schoolers should be trained in CPR, and should be trained in hands-off or hands-only, excuse me, hands-only CPR. You don't have to do mouth-to-mouth anymore, so it's not just iffy. If you learn it in high school, it's not that complicated, and I think all of the players should all know CPR. If you're in a team that plays lacrosse or football or anything, CPR is so crucial because CPR perfuses the brain while you're waiting for the defibrillator to get there. In Demar's case, I think it was seven or eight minutes before he got defibrillated, but they had to have done superb CPR because his brain survived. If you remember that soccer player in Europe, Mumbo, they did CPR on him for 47 minutes, and he walked out of the hospital with no neurologic defects a week later. Good CPR, know where your AED is. The coaches should not only have CPR, but AED training, and I don't see any reason why you can't do CPR and AED training for every high school in their health class. Just don't see why you can't. Well, I'm a fan of that, I agree, but Mark, wonderful discussion, and thank you for the really groundbreaking research you did in this area years ago. Who knew it would come back to be on an AP show, right? This is an arcane subject. I was on a text with people when it happened, and they were texting me, what happened, what happened? I said, I don't know, I'm not sure yet, it could be a lot of things, but it could be commercial court. I said, I got all these like, what, what, what are you talking about? It was my five minutes of fame. I sent him a reference to your article, then I realized, what am I doing sending this to a non-cardiologist? Great. Mark, thank you so much for your research. Thanks for having me. Yeah, it's been great. Thanks. Take care of yourself. Bye.

commotio cordis

sudden cardiac death

ventricular fibrillation

adolescence

CPR training