Disclaimer: I joked in our previous post that we would need a disclaimer, and sure enough, we did! This post is updated from the one that was posted yesterday, in response to a comments regarding terminology and statistics. So before we begin, we clarify some definitions:
A Heart Attack is caused by a circulation or plumbing problem in the heart, while Sudden Cardiac Arrest is caused by an electrical problem in the heart.
In our last post, we used the term heart attack, and were informed that this was incorrect, and should have been cardiac arrest – we disagree with the ‘incorrect’ part, though we acknowledge that sudden death during exercise can have electrical explanations, and so perhaps ‘incomplete’ would have been more appropriate! Our focus in the post is primarily on the circulatory causes which we believe are still more prevalent, according to literature on runners (see the Jim Fixx section). In this post, then, we speak of heart attacks. I’m sure the ‘purists’ will shudder, but this is not a peer-reviewed journal article, so we have to take certain liberties or we would end up writing a thesis that no one would read – one of the problems with science, sometimes. Perhaps in the future, we’ll do a separate post on electrical disturbances…
Jim Fixx, Alberto Salazar, Alem Techale, 2 Comrades runners this year.
Perhaps you recognize some of these names, others not. But they all have two things in common. First, they suffered heart attacks/sudden cardiac arrests (heart attack from now on!). Second, they are athletes (different levels, sure, but athletes nonetheless), and their heart attacks happened while they were running.
Most recently (2 weeks or so ago), Alberto Salazar, winner of the 1994 Comrades Marathon, winner of the 1982 Boston Marathon, three New York Marathons, and former world record holder, suffered a heart attack aged 48 during a coaching session. You can read more about this story here. Salazar recovered, the others were not so lucky. Famously, Jim Fixx, who wrote the book The Complete Book of Running, died at the age of 52 during a training run in 1984. Alem Techale, fiancé of Kenenisa Bekela, collapsed during a training run in 2005.
These events tend to be emotive topics, because they shatter the perception that the fit among us are immune to this problem – the world record holder, a man who runs 50 miles a week, having a heart attack! Surely not? So what we at The Science of Sport thought we would do is take a look at the physiology and medicine of sudden death and heart problems during running. This is of course a very complex topic – this post should come with a disclaimer – it can’t possibly cover all the options, but it does present the most common explanations for what we all read about with shock when the ‘ambassadors’ of healthy living are struck down by what we see as a disease of the unit.
The history of our perceptions
In the 1970’s, the American Medical Joggers Association (yes, it’s a real name!) published a report in which they claimed that not a single marathon runner had died due to a disease called coronary artery disease – in this disease, the arteries that supply blood to the heart become narrowed by cholesterol deposits inside them, and the heart’s blood supply can be restricted. It’s a common cause of heart attacks.
The conclusion made by the AMJA, led by a scientist named Bassler, was that marathon running provided immunity against coronary artery disease and heart attacks. This became known as Bassler’s hypothesis, and it contributed to the “running boom” of the 1970’s.
However, by the mid-1980’s, cracks began appearing in the façade. Two deaths during training were reported by scientists from UCT, and so the “protection” theory was questioned. In 1984, data were published showing that 75% of athletes who died during exercise had signs of severe cardiac disease, effectively disproving the Bassler hypothesis.
That’s not to say, of course, that regular exercise is not beneficial, because it is. There is a wealth of research that suggests that regular exercise improves heart health. But the net result of all these studies was that while a marathon runner is less likely to develop coronary artery disease, they are not immune.
How often does it happen?
So with that in mind, how often does a heart attack during exercise happen? Without wishing into going into too much detail, studies have looked into this and found that the risk of sudden cardiac death is incredibly low, much lower than it is for the “normal” population. For example, one study in Rhode Island found that there is one death per 7620 runners PER YEAR. That is incredibly small – remember, a “normal”, non-running group of 7620 people has a much higher chance that at least one person will have a heart event per year. Another study found that the risk of death in a group of runners was about 1 in 50 000, or 1/100th that of a non-running population. Those are odds I would certainly want in my favour!
So what MIGHT HAVE happened to Salazar?
It’s impossible to answer this question of course, his doctors would probably know, I’m just guessing. Also, we don’t want to write a thesis here, so we take some liberties with the full story, but we will put out a few possibilities (remember our disclaimer…?)
Studies from the 1980′s and 1990′s have found that virtually all the runners who die suddenly during exercise are suffering from some sort of serious heart disease before their fatal heart attack. There are probably about 30 possibilities, but we’ll focus on one or two.
Coronary artery disease (CAD)
The most common one by far is coronary artery disease, or CAD, which we mentioned earlier. This is where the blood vessels supplying the heart become ‘choked’ due to cholesterol plaques that form over the years. This is the main cause of death in runners older than 35 – the plaques take time to form and eventually completely block off the blood supply to the heart. The heart, of course, can’t function without the blood and the muscle dies as a result. It’s quite logical to see how exercise, if not controlled, will contribute to a heart attack, because the demand from blood and oxygen by the heart is greatly increased, and there’s also more chance of a plaque being dislodged and blocking the vessel completely. This is what happened to Jim Fixx, with the autopsy showing that one coronary artery had 95% blockage, a second 85%, and a third 50%.
This, by the way, is also the reason why people with high blood pressure or CAD should not do heavy weight training – the blood pressure rises drastically during weight training and this can cause the plaque to break off, causing a heart attack. So people with high blood pressure or CAD are better off doing cardiovascular type training, where the blood pressure rises far less.
In people who are younger than 35, the cause of death is more likely to be what is called a congenital cardiac abnormality. There are loads of these, and then include something called hypertrophic cardiomyopathy (apologies for all the medical terms and lengthy words). This is basically a disease where the heart muscle grows in size (that’s what Hypertrophy means) to the point where the blood supply is not sufficient to meet the demand, and the overgrowth of the muscle interferes with the ability of the heart to contract and relax. In other words, a large muscle needs greater blood supply and this can’t be met. There are reports, for example, of cyclists who increase the size of their hearts through training and eventually reach the point where they cannot supply enough blood to the muscle. So in some people, the size of the heart muscle is simply too large to supply blood to, and the muscle becomes diseased as a result (this is the cardiomyopathy part).
In young people, there is also something called familial hypercholesterolemia – as the name might suggest (by the time you finish re-reading it!), this is a condition where you can inherit (familial = family) high cholesterol levels. So when a young athlete dies, it’s possible that they have the coronary arteries of a much older person, purely as a result of their genes. This is of course also a major factor for older runners – Jim Fixx’s father suffered from two heart attacks, one aged 35 and the second (fatal) one at 42. So his problems were certainly related to heredity.
There are of course many other possibilities, include abnormalities in the arteries, and diseases with exotic-sounding names like dysplasia, Marfan’s Syndrome, and myocarditis. Then of course,there are the electrical disturbances, including arrythmias and channelopathies. But this post is technical enough without details on these. So we’ll settle on CAD and hypertropy. If there are any specific questions, we’d be happy to attempt to respond, but we’ll leave the technical stuff there!
But before we move onto the practical information and message, it’s worth also pointing out that heart attacks can also be caused by exercising with a viral infection. This can cause a virus to infect the heart muscle (myocarditis) or the pericardium (a membrane around the heart – pericarditis). When this happens, the athlete can die even though they are otherwise healthy. So if you have flu symptoms, this is the critical reason why exercise is not recommended. I’ve heard reports that a lot of the elite cyclists in Europe die young because the nature of their sport demands that they often race when carrying a viral infection like flu. Fortunately, most of us are not in that position, so we can take the sensible option and rest!
Ignoring the warning signs
Now, onto the more important stuff – how do you avoid this, and what do you do with this information? A key point is that a lot of people ignore early warning symptoms, literally running into further trouble. The main early warning signs are chest pain, excessive shortness of breath, and abdominal pain. One story, documented in the literature, actually found that a runner did a 64km training run with severe chest pain, which forced him to walk numerous times, before doing the Comrades Marathon. During Comrades, he suffered a fatal heart attack. It’s been reported that about 81% of runners who suffer heart attacks during running had experienced and ignored chest pain or some symptom before “the main event”. So the bottom line – don’t ignore the signs!
So where does that leave you as a runner?
Assuming you’re a runner, then, you’re in a pretty strong position. But not an invincible one. Research has shown that in those people who have some sort of undetected heart disease, the risk of sudden death during exercise is massively reduced by regular exercise training. However, these people are more likely to have a heart attack while they exercise than while they are at rest. Hopefully that is clear – exercise reduces the overall risk by a factor of almost 100, but if the runner has a condition that will cause a heart attack, there’s a greater chance of it happening while they exercise. So as a regular runner (we hope!), you can be happy in the fact that you are about 100 times less at risk that your non-running colleagues. But you are not immune and so looking after the health of your heart, which includes checkups and tests, is still important, so that any symptoms of heart disease can be treated early. And should you stop exercising because you MIGHT be at greater risk? Well, no, because the data show that if you do this, and stop training, then your risk goes up massively. So no matter which way you look at it, it’s far better to continue running and training. In fact, if you’re reading this and you may have some sort of coronary artery disease, then you, of all people, would be best off by doing regular exercise, because the beneficial effect is the greatest.
So keep running, be aware, educate yourself and never take chances. Any chest pain, any shortness of breath, have it checked out. But don’t stop running. I’m sure that’s how Jim Fixx would have wanted it. The famous runner and author, who wrote some of the definitive books on the running “boom” of the 1970’s once wrote
runners are much like ordinary mortals. They can, sad to say, get sick. They can even die.
True, but less often and with reduced risk compared to non-running ‘mortals’, so keep running!
R & J