Running 26.2 miles is a tremendous physical accomplishment; it can also take a toll on the body. When a person runs a marathon, the heart pumps about seven times as much blood. All that stress can lead to cardiac arrest. It's extremely rare, affecting only one out of 184,000 runners, but many others may be at risk.
Peter McCullough, MD, MPH, Cardiologist at Baylor University Medical Center has run a marathon in all 50 states. He's got the trophy to prove it. But two years ago, he stopped running marathons.
Dr. McCullough told Ivanhoe, "For some individuals the excessive exercise and endurance training and racing at the marathon level can directly cause heart muscle damage."
After the 2007 death of Ryan Shay, who collapsed trying to qualify for the U.S. Olympic team, Dr. McCullough and a research team conducted studies on marathoners. The team used MRIs and blood tests and found indicators that up to 25-percent of marathon runners could be at risk for scarring in the heart. In rare cases that can lead to cardiac arrest.
"Great runners have died, and there's been an interest in the medical community to ask the questions why," said Dr. McCullough.
All marathons now have first aid and defibrillators on site. Dr. McCullough also recommends more research efforts including a national research registry of runner's who have had heart problems, as well as blood tests before and after marathons, and heart MRIs.
Dr. McCullough says people shouldn't stop running, but for some, running and walking a shorter distance may be safer.
According to the New England Journal of Medicine, 11 million people ran marathons between 2000 and 2010. There were 59 cardiac arrests.
Contributors to this news report include: Cyndy McGrath, Supervising Producer; Don Wall, Field Producer; Cortni Spearman, Assistant Producer; Mikon Haaksman, Videographer and Jamison Koczan, Editor.
BACKGROUND: Marathon running has become increasingly popular, and although running is good for you, research has shown that putting that much stress on the heart could cause damage. Although rare, there have been cases of runners dying either during or after a marathon. Researchers found that even as participation in marathon racing almost doubled during the past decade to more than 473,000 finishers in 2009 from about 299,000 in 2000 the death rate remained unchanged. A total of 28 people died during or in the 24 hours immediately after a marathon, most of them men, and primarily from heart problems. A few of the deaths were due to hyponatremia, or low blood sodium, in those who drank excessive amounts of fluid. The researchers found 59 cases of cardiac arrest during a half or full marathon, 51 of them in men, and 42 of them fatal. The average age of the affected racers was 42, and an overwhelming majority of them were approaching the finish line when they fell. Doctors say genetics, viruses, bad habits from the past or bad diet can also come into play when it comes to deaths from running marathons.
(Source: http://well.blogs.nytimes.com/2012/05/23/is-marathon-running-bad-for-the-heart/?_r=1)
RYAN SHAY: Ryan Shay was an American professional long-distance runner who died tragically in the first 10k of the 2007 U.S. Olympic marathon trials in New York City. Doctors reported that Shay died of a massive heart attack due to a pre-existing enlarged heart condition but the autopsy report concluded that he died of a cardiac arrhythmia due to cardia hypertrophy with patch fibrosis of undetermined etiology, or natural causes. At the age of 28, Ryan Shay, ranked number nine in the U.S., died of a heart attack.
(Source: http://en.wikipedia.org/wiki/Ryan_Shay)
WHO SHOULD RUN MARATHONS: Doctors say that people should not stop running marathons, but for some, shorter distances may be safer and less stressful on the heart. Peter A. McCullough, MD, MPH, Cardiologist at Baylor University Medical Center says that those with abnormal findings on heart echocardiograms, MRI's and other tests should only run as advised by their doctors. If you have any symptoms of heart problems, like chest pain, dizziness or unusual fatigue, you should see a doctor, no matter how fit you believe yourself to be.
(Source: Peter A. McCullough, MD, MPH)
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Peter A. McCullough, M.D., MPH, Internist and Cardiologist at Baylor University Medical Center in Dallas, talks about the effects that marathon running can have on the heart.
Interview conducted by Ivanhoe Broadcast News in December 2014.
You're a renowned marathon runner right? This is a huge accomplishment.
Dr. McCullough: I was recognized in 2012 after completing a marathon in every state in the United States and there have been a total of about 3,000 people since 1970 who have attempted this feat and they're have now been about 600 who have achieved it over the last 40 years.
That says something not only in terms of your accomplishment, but it says something about the number of people running marathons.
Dr. McCullough: There's been quite an increase in the number of people running marathons. From the 1970s, the estimates were about 70,000 finishers in the United States and now we're upwards of a million finishers per year. It's very popular among young people and increasingly popular among women.
For the most part, the general impression is that running is really good for you?
Dr. McCullough: Sure. There is wealth of information suggesting that running, out of all the exercises that one can do is the most efficient in terms of burning calories per unit of time and is the form of exercise that makes individuals feel the best. That's the reason why it's so much better than cycling or using an elliptical. It's the most efficient, it makes you feel the best and it is the form of exercise that gets people outside of buildings most frequently and so many have said that if there's a king of exercise that it's running from a personal health perspective.
The marathon is the standard of excellence for running?
Dr. McCullough: Sure, the marathon is considered the pinnacle of running and the U.S. Track and Field Association keeps track of all the races going on in the United States and certifies races. Races are very popular for raising money for various causes. They're popular during holidays. In fact, in two days, I'll run a 10K Turkey Trot on Thanksgiving in the spirit of running. But the marathon is special and has a history that goes back to ancient Greece where a Greek Harold named Phidippides ran a great distance and in fact when he came to deliver the message to the Greek leadership about defeating the Persians, he collapsed and died during the marathon. The final distance he ran was 26.2 miles and it became memorialized as the marathon distance.
He ran a lot more than that didn't he?
Dr. McCullough: Right, the estimates over a few days is that he ran about three times that distance.
The bottom line is he did collapse at the end of the run. What happened?
Dr. McCullough: No one knows back then what happened, but the thought occurred in history that someone in top health, a professional runner if you will. He was a herald and that's what messengers did back then is they ran great distances. It was a shock that it was possible that one could suddenly die after a prolonged period of running.
In the 70s when the running craze really took over, everybody became a runner and it became probably our top type of exercise. A lot of marathon interest developed out of that. Historically, some great runners actually did die from it.
Dr. McCullough: Great runners have died and there's been interest in the medical community to ask the questions why and there are some answers. The most common cause of sudden death during forms of exercise is called hypertrophic cardiomyopathy or a thickness of heart muscle. Other causes include congenitally misplaced coronary arteries or a congenital electrical problems or even early cholesterol blockages of arteries, but what has concerned researchers in the last few years is the possibility that one could die during an exercise event and not have any of those causes.
Somebody that is in seemingly perfectly good health, that doesn't have some of those other issues like a congenital problem with the heart, could still collapse during a marathon?
Dr. McCullough: Correct, the sentinel event in recent history was the death of Ryan Shay who was from Ypsilanti, Michigan. It was in 2007 in November. He was running the qualifying race for the U.S. Olympic team and he died at mile 6 in Central Park in New York City. In the autopsy, it was found that he had an abnormality in the heart muscle suggesting a scar in the heart muscle itself without any of the other problems that I mentioned. One of the questions that was raised is could the exercise chronically over time cause scarring in the heart and research had been done for years with the Boston Marathon, and it began to suggest, using cardiac ultrasound, that there could be dilation of heart muscle chambers. Other research suggests that there was release of damage proteins called troponin as well as a stress hormone called BNP into the blood stream with marathoning, In 2010, I became involved in research because I was an active marathoner myself and one of my trainees, Justin Trivax, MD, did a very high quality study of the Detroit Marathon and he invited randomly selected marathoners to participate in what is now the most detailed cardiac study performed on marathon runners before and after the race. . The random selection allows us to get a fair assessment by chance of what these marathoners looked like in terms of their hearts. What he demonstrated is that 25% of marathoners have, after running a marathon for 24 hours approximately, dramatic dilatation of the right ventricle and right atrium and that puts strain on the other cardiac chambers. It's that same 25% of individuals that has a rise in troponin and BNP and we do believe that that is in a sense a pathologic response to this endurance event and the runners themselves couldn't feel it. They wouldn't otherwise know it unless we had literally grabbed them at the end of the race and we took them into a cardiac MRI scanner and scanned the heart.
Can you explain that in very simple terms?
Dr. McCullough: You can think of the heart as a simple pump. At rest, the heart pumps five liters per minute of blood. During running, the pumping function of the heart increases to 35 liters a minute. That's a sevenfold increase in the amount of blood pumped. That creates a tremendous strain on the heart and we believe in about a quarter of people who attempt an endurance event the heart simply can't take that degree of overload for that long.
What happens?
Dr. McCullough: When the heart begins to fail in terms of managing overload, chambers dilate and when chambers dilate, the sections of the heart begin to dilate, it puts strain on other areas of the heart and chronically over time, that can cause changes in heart muscle cells to lay down scar.
Is there a problem with the scar? What's the difference if you have a scar?
Dr. McCullough: If you look on your skin and you have a scar, you'll see a white line or you'll see something that interrupts your normal skin pattern. Well when a scar is present in the heart muscle, it interrupts the normal electrical pattern. We believe in Ryan Shay's case, and in some runner's cases, about one in every 50,000 marathon runners who drops dead in the United States per year, we believe the problem is the electricity is going around the scar and forming a very rapid circuit. That rapid circuit is called ventricular tachycardia, when that starts, the runner begins to feel dizzy because the heart's going now very fast and it degenerates into ventricular fibrillation and ventricular fibrillation is a full cardiac arrest so what we'll see is runners running, and they get dizzy and then when they fall down, they go into complete cardiac arrest and unless the heart is shocked right then and there, after about five or six minutes, that cardiac arrest becomes permanent and there's a death. The scar leads to ventricular tachycardia which ultimately leads to the spiral of death unless that person is lucky enough to actually have the heart shocked with a defibrillator.
Does that mean that at every marathon now, first aid tents are available and are being used more and more?
Dr. McCullough: It's quite a telltale sign that at every marathon there are paramedic units available at the finish line and in fact some marathons now have paramedic units strategically located around the course. Now, that can be for bumps and bruises and sore joints and what have you, but their real function is to try to respond very quickly to someone passing out in the event of ventricular tachycardia and ventricular fibrillation. The problem with the marathon is that it's 26.2 miles and there have been stories where a runner is found down and another runner has to go alert help and may have to run another mile or two to find help and then get the paramedics there and try to resuscitate that individual. There have been tremendous stories in the United States of first aid runners and in fact the Boston Marathon now has a pre-marathon training course for health professionals where they go through training for when someone goes down what should other runners do in order to try to help save that individual.
Is running dangerous?
Dr. McCullough: We don't want to give a sweeping public health message in the point in time where the research is early. We're simply making observations that it is possible for someone in the picture of health with a completely ostensibly normal heart to have the endurance exercise itself cause the substrate for and then ultimately trigger that sudden death. Having said that, we believe like everything else, exercise is like a drug in a sense. One can do too little and one can do too much and there's probably a happy spot of moderation. It's been said, do everything in moderation. It's probably true for exercise. The best forms of running are probably where somebody runs for a period of time and then rests and then runs again. That probably is quite fine and beneficial. It's just that when we start taking cardiac output up to 35 liters a minute for four straight hours without rest, that's probably too much for some individuals no matter the level of fitness.
This puts a whole different spin on the entire picture of what it means to be healthy.
Dr. McCullough: It's quite a strong call for additional research. In my view, we do need a national registry of marathoners and certainly those who have had passing out spells and cardiac arrests during marathons. We need science applied to the theory that exercise itself could promote scarring in the heart and that scarring could lead to arrhythmias. We do need solid science behind that and we clearly need approaches to the public to screen for individuals at risk. Our data suggest 75% of individuals are not at risk at all. In fact, their hearts look great during a marathon. It's only 25% that are at risk where the blood tests turn positive, the MRI has these changes, and maybe we can come up with an approach for these individuals at risk. We can give them guidance towards healthier forms of exercise. I think the futures' quite bright. Early data suggests even when there is a scar or fibrosis there, it potentially can heal itself. I personally, based on data in 2012, stopped marathoning. I stopped marathoning because; I accomplished my goal in running all 50 states and also running in Asia, Europe and in Canada. But I also stopped because I personally was concerned. I was concerned that maybe I was doing what's happened to so many others, that I was promoting changes in my heart that in the end I'd regret.
Did you go through the trouble of having an MRI done on your heat to make sure that you were not in the 25%?
Dr. McCullough: MRIs are quite expensive and unfortunately, I have not had an MRI of my heart but I did on one occasion have the blood testing done for BNP and troponin and fortunately, those were normal after a marathon. I have to tell you, after racing across the United States, running in all 50 states was a great way to see the country, I did run a race one time in Missoula, Montana, and I finished at about the same time another doctor finished. He was a gynecologist and we were talking, we were actually very hot and we were in these outdoors showers afterwards and I stood next to him and he said "Well listen, I have to go now, I have go to the hospital." And I said, "Go to the hospital, what for?" He replied, "Well it's just down the street. We're in downtown Missoula." He said, "Well, I'm going to go in there and have my blood tested." That was back in 2008 or 2009, by that time, it was known from research from around the world that the blood tests may give us a clue on whether or not the marathon caused heart damage.
What's available for a person who is serious about marathon running and they want to know up front if they're okay to run?
Dr. McCullough: There are no guidelines to inform us, but I would suggest a cardiac MRI with a contrast agent we give by IV called gadolinium, to see if there's any evidence of scar formation in the heart. The MRI would also pick up these other abnormalities including abnormal heart muscle thickening.
But that would be an elective, right? Insurance probably wouldn't pay for that unless there was a reason for it.
Dr. McCullough: Right, there wouldn't be a standard insurance indication for that test. I think the other thing that can be informative is a baseline cardiac troponin blood test and cardiac BNP and then one as soon as we can after the marathon. It's typically elevated, stays elevated for about a day before it goes down. That would be useful to understand whether or not that individual is in the 25% of individuals where there's an abnormality discovered.
Does that blood test have to be done right after the marathon or is it something that could be done during your annual physical?
Dr. McCullough: No, it would have to be done within the first 24 hours after the marathon and these tests are typically emergency blood tests. They're done in the emergency room. There are now platforms where they can be done with a point of care. It can be done with a small instrument right at the site so some of the research now at the Boston Marathon does that, where marathon finishers complete the marathon, they actually have the blood checked right there.
Do you think that's something that could become a standard type of thing down the road? It sounds expensive.
Dr. McCullough: No, the tests are actually very inexpensive. If research confirms that the blood tests really do identify individuals at this theoretical risk it potentially could become a standard. When all marathoners' sign up for a race, they actually have to sign a medical disclosure saying that they understand the risks. Unfortunately, on our side, we just can't inform individuals of the risks. We know that the doctor's examination, a standard EKG done on a physical or a standard stress test in most circumstances is not informative.
Exercise is good, but too much at least in this specific way, could be harmful?
Dr. McCullough: I think the take home message is that for the population at large, of which, a large number of individuals are completely sedentary, going from sedentary to doing some exercise, is a very beneficial thing. In fact, regular moderate exercise is very beneficial. But research in the last few years as well as careful observation of marathon runners in particular suggest that for some individuals the excessive exercise and endurance training and racing at the marathon level can directly cause heart muscle damage that can lead to cardiac arrest and death.
In other words if you don't have the test and you want to get into it you're taking your chances, right?
Dr. McCullough: One always takes their chances as soon as you take your first step you take a chance and in fact the odds of death with motor vehicle accidents or other things is far higher. When I went to the 50 States Club awards ceremony in Fort Worth, Texas for completing the all the states, one of the individuals in my graduating class had a cardiac arrest in one of the marathons. He had a defibrillator implanted and he kept on running to complete the 50 states and in fact he was so grateful to be in the 50 states club because other members did CPR on him until the paramedics came and shocked his heart. He showed everyone where his defibrillator was in his chest. He was a great example of the idea that the marathoning itself can become an obsession with little regard to a brush with death. There's actually a research registry of individuals who have implanted defibrillators and there are two examples where runners during the course of a marathon have had a collapse into cardiac arrest, the defibrillator has shocked them and they've gotten up and finished the marathon.
I suppose we're all going to die somehow.
Dr. McCullough: Right, that's true, but the idea is should we pay the ultimate price early in life in the picture of health just because we haven't received enough guidance from the running community or from the medical community. In my view, all of this really is a very strong call for an intensive research effort because marathoning is now so common particularly among young people.
Does there need to be a warning label when you buy your sneakers?
Dr. McCullough: I don't think we're at the point where we can give a warning label for endurance sports, whether it is a half marathon, or marathon, or a 10K or a 5K. We don't know because there are so many other factors involved and commerce is strong. There's the whole running shoe business and marathons bring a lot of money to cities and all the hotels and restaurants. We'll have the Dallas White Rock Lake Marathon in December and the whole city will be alive. It's really a tremendous event and hopefully there won't be any deaths during the marathon, but we'll only know until the event is done. What we want to see happen though is enough interest at the National Institutes of Health, American College of Sports Medicine, American Heart Association, or at the philanthropic level where we can have a group of scientific leaders who can agree on the right methods to study this problem and ultimately give the population reasonable sets of recommendations so we can avoid this tragedy in the future.
Some people would say, well why worry about it, it doesn't affect enough people.
Dr. McCullough: If you take a city where a marathon is being done, if one person dies in the marathon, there'll be 15 other people dying in the same city at the same time of a heart attack or a blood clot to the lungs or other terminal illness, but the point is these individuals who are running these races are the epitome of health. The average person is at their peak of life, their peak earning capacity. There's just no reason. In many ways, it's an avoidable death. I've heard these arguments from experts who simply say it's rare so let's not worry about it. In this circumstance, in my view, even the rarity of it, doesn't mean we should minimize it. I think we should study it. We should understand it and give reasonable recommendations. In the future, hopefully prevent these tragedies to families' altogether.
Because the full marathon is such an entity now, is cutting them down an option?
Dr. McCullough: No, I don't think we can cut. In fact, there are distances much greater than marathons. There's an ultra-race where its 50 miles and I was involved in the making of a movie that covered individuals who ran three marathons in a row. Believe it or not, the extreme distances may not be as harmful because once we get beyond a marathon distance, almost everybody has to do some walking and when you have to walk, then cardiac output comes down, all that strain comes off the heart and then you start running again. Marathoning is the distance is considerable but still short enough where one can run it all the way through without walking. There is a theory that if we simply ran some and walked some, and let that strain come down off the heart and then run again, that would be a healthier approach and in fact that maybe the case.
But it wouldn't make for a good marathon?
Dr. McCullough: There have been studies that suggest for the average marathoner like me in their 40s and 50s that the time would be about the same believe it or not whether it is run straight through or if walking breaks were inserted.
For the guys that are going for the win, they've got to keep going.
e He He said itw as He said itw as Dr. McCullough: The winners can't walk and run, but for the average participant that may be a reasonable approach. We may have in the future, if we were to fast forward five or 10 years, a circumstance where medical technology can clearly identify a group of individuals who absolutely positively should not run continuously for 4 hours. . We may have another group of individuals in whom, it may be best to walk and run. There is probably a large proportion; I would say 75% or more that we can simply say you're fine, go for it and run all the way through the race.
It would be nice to have that up front wouldn't it?
Dr. McCullough: It would be great.
That would be the panacea for the future right? We'd be able to have that information before you start.
Dr. McCullough: Right, the medical term for that is called risk stratification. Risk stratification is that we simply want to identify risk and then inform individuals so they can know. I don't think it's going to be a one size prescription for all. It's not going to be like wearing seatbelts where everybody has to wear a seatbelt. There clearly are individuals who can just go for it. It's absolutely open to them. There is about a quarter of individuals who could be at risk. We need to study them more and there are some who we believe really shouldn't do the activity period. They should have other activities or they should take a different approach like walking and running.
The criteria or the reason that 25% might be at risk is genetic?
Dr. McCullough: It could be. We know that there is a very rare condition where the proteins that connect the heart muscle cells are very defective and the heart chambers dilate considerably. There may be minor variations, genetic variations that are more permissive for heart chamber dilatation during chronic overload. It's purely conjecture at this point in time, but my hunch would be that about 25% of us do have that genetic permissiveness that our hearts can be overloaded with four hours of continuous exercise and have this dilatation of the heart chambers that we observed on cardiac MRI.
Is there anything that you would like to add?
Dr. McCullough: I think one final point is that exercise as a general rule is very beneficial when it is practiced over the course of a lifetime. There have been studies of marathon runners who throughout the course of their life are far healthier than the average person on the street. There's no doubt about it. They are healthier. They live longer. In fact, one of the great myths is that marathon runners wear out their joints sooner. I'm quite convinced at my age that I've taken on average about four or five times as many steps as the average person will take in their entire lifetime and my joints are perfectly fine. Marathon running does not wear out the joints and people are incredibly healthy compared to fatter and more sedentary individuals. It's the risk of sudden death that we're worried about during racing that we really have to make a top tier priority in the exercise research community.
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