Earlier today, we brought you a very abridged summary of today's US Olympic Trials marathon in
Sudden death during exercise (and particularly running) has dominated recent news in running, with the collapse of Alberto Salazar earlier this year, followed by the collapse and death of a Spanish football player Antonio Puerta in August, and then most recently, the death of Chad Schieber in the 2007 Chicago Marathon
These events always shock us to the core, because we naturally believe that athletes, especially the elite, are protected against these events. When some of the fittest men in world collapse doing the very activity that is supposed to protect them, it sends a wave of anxiety and doubt through us all. And here at the Science of Sport, we've tried hard to bring you the scientific insights and interpretations of these events.
With the tragic death of Ryan Shay (you can read his profile and bio here), it is of course far too early to diagnose anything. In fact, one of the trickiest and most difficult things about these events is that the cause of death often cannot be established, particularly in the event of some electrical disturbance (arrhythmia). So we must wait on the autopsy result before committing to any analysis, but we did think that perhaps it would be informative and educational to very briefly run through some of the possible medical events and complications that might have contributed to the death of Shay.
Of course, this is very preliminary and is certainly not a diagnosis. Nor is it comprehensive and we acknowledge that we cannot possibly cover everything in this post - it is simply too vast a topic to hit in one go. But we'll do our best to present that information as it becomes available. Until then, our brief look at some of the possibilities...
Introduction to sudden cardiac death - we need a definition
Perhaps surprisingly, there is no universally accepted definition of sudden cardiac death. When we did our post on Alberto Salazar, we drew a response from someone who wanted to point out that heart attacks and cardiac arrests are quite different events. We agree completely and never stated otherwise, and what happened to Salazar was a heart attack, which is defined as a circulation problem. In contrast, sudden cardiac arrest is an electrical problem in the heart.
At this very early stage, taken in isolation, it would appear that Ryan Shay's death falls into the latter category - a cardiac arrest, since most Sudden Cardiac Deaths (SCD) in athletes younger than 35 are caused by these electrical disturbances. In contrast, the heart attack is most often to due Coronary Artery Disease (CAD), something that is usually prevalent in older athletes (over 35). Shay was 28 years old, and so while we again make the disclaimer that we must wait for a proper autopsy result, it would appear to be on the side of cardiac arrest.
The one confounder to this argument is that Shay is reported to have received almost immediate treatment, including defibrillation. Again, I'm not sure that this did happen, or how quickly, but if it was immediate and failed to help, then perhaps we are loooking at a circulation problem? All speculation of course. We covered the circulation possibility in our post on Alberto Salazar a few months ago, so you can read about that there. In this post, we focus on electrical problems.
So the definition for SCD is a "Non traumatic and unexpected sudden cardiac arrest that occurs within 6 hours of a previously normal state of health." That's obviously a vast and all-inclusive definition, but it highlights the reason why these sad events make such an enormous impact on us all - the athlete may have been 100% healthy and normal only hours befor the race, with no known evidence of any abnormality or risk factor for disease.
How often does it happen?
Again, this is a tricky one, because there is no database to track the prevalence of SCD during exercise in young athletes. The largest available studies have estimated that it lies somewhere between 1 per 200 000 and 1 per 1 000 000 athletes per year, which would seem incredibly rare, but it must be borne in mind that this is probably an underestimation, because it's so difficult to diagnose afterwards.
Around 30% of all non-traumatic deaths are due to SCD, with about 30% of the victims being younger than 65 years. Most of the cases (80% or higher) happen either during or immediately after exercise, and it is often the physical activity that may trigger the cardiac arrhythmias. We'll look at this a little later on in this post.
Looking at cause - a very broad overview of the possibilities
Again we must make our disclaimer that we cannot provide an exhaustive list, but hope it's instructive to look at some of the available knowledge on this topic.
To begin with, in most SCD cases, there is a common pattern at the end - you have a combination of exercise and some underlying (and undetected) heart disease which leads to what is called a fatal arrhythmia. Effectively, some underlying condition (structural or electrical) causes the heart to 'degenerate' into a chaotic and abnormal rhythm, and when this happens, the pumping function of the heart is severely compromised.
The list below shows some of the more common causes or underlying conditions that account for SCD in younger (<35>
- Hypertrophic Cardiomyopathy (36%)
- Congenital coronary anomalies (17-19%) (WE WILL LOOK AT THESE TWO IN MORE DETAIL)
- Idiopathic left ventricular hypertrophy (ILVH) (9% -10%)
- Aortic rupture
- Arrhythmogenic right ventricular dysplasia
- Aortic valve stenosis
- Prolonged QT syndrome
- Mitral valve prolapse (MVP)
- Commotio cordis
- Wolff-Parkinson-White (WPW) syndrome
- Atherosclerotic coronary artery disease
We won't look at all these---it would be a thesis to do so---so instead, we'll look at one or two in the interests of discussing some of the more likely explanations. Again, this does not suggest that Shay's death could not be caused by any of the others, or indeed possibilities not on the list.
Hypertrophic Cardiomyopathy (HCM)
This is the most common cause of SCD in younger athletes who die during competition. The condition is characterized by a thickening of the heart muscle (myocardium), which means the demand for blood flow is increased. When the blood flow is restricted, the myocardium becomes unstable and the fatal arrhytmia can occur.
The frightening thing about HCM is that it goes undetected an incredibly high percentage of the time. It is estimated that the condition occurs in about 1 in 500 people, yet the diagnosis is only made in about 1 in 30,000 cases! That is an extra-ordinarily low diagnosis rate. A really difficult issue is that athletes will naturally have larger hearts as a result of training. So when an extremely fit young athlete dies (as was the case with Ryan Shay), the diagnosis is made a little more complex by the fact that the heart muscle is enlarged anyway.
HCM is usually a genetically transmitted condition, but it expresses in varying degrees. The problem, apart from the very low detection rates, is it may not manifest itself until adolescence or even early adulthood, and for that reason, many young athletes may have nothing wrong until the condition manifests itself. The first clinical manifestation (that is, the occasion on which the condition presents itself) is death.
However, research has also found that about 21% of the athletes who die from this condition (which can be diagnosed after the event) did complain about symptoms, which can include chest pain, exertional shortage of breath (dyspnoea), light-headedness, and fainting.
Coronary artery abnormalities
These are the second most common cause of death, and there are a few possible abnormalities in the category. Again, the problem is that these are very rarely diagnosed during life. The coronary circulation, incidentally, is the part of the circulation that provides blood to the heart muscle (as opposed to the pulmonary to the lungs and systemic to the body). So when there are abnormalities in the coronary circulation, the blood flow to the muscle can again be compromised---much in the same way that HCM can cause the same thing.
So what happens here is that there are structural problems, where the connections between the arteries in this coronary 'network' are abnormal. This can cause arteries to become compressed, and again fail to provide sufficient blood to the heart muscle, leading to the development of potentially fatal arrythmias.
As is the case for HCM, the majority of cases are only diagnosed after death, if at all. In 31% of the cases, symptoms were discovered retrospectively - these again include fainting and angina (characteristic chest pain).
Therefore, as with HCM, it is another condition where some symptoms may be noticed, but never acted upon. As an elite athelte, shortages of breath, and over-exertion which may cause severe discomfort and often almost cause the athlete to faint are nothing new. Also, elite athletes tend to be 'wired' or conditioned to ignore these symptoms and push on past the pain and discomfort. For this reason, it is possible that athletes such as Ryan Shay felt some symptoms, regardless of their condition, but sadly ignored them, perhaps attributing them to normal "training pains," with tragic results.
Another possibility - myocarditis
One final possibility that we must mention is a condition known as myocarditis. This is, as the name suggests (the -itis part suggests it) an inflammatory condition of the myocardium (the heart tissue). It is most often associated with a viral infection, which can then affect the heart muscle.
The problem here is that the elite athlete, who may well have a good deal riding on the event (financial, prestige, etc) will often choose not to rest when they have a viral infection. For this result, they are perhaps vulnerable to this kind of condition. If one looks at an athlete like Ryan Shay, who may aspire to a place in the Olympic Games, who has perhaps dedicated a full year of training to this one race, to sit out for a slight infection would not perhaps seem feasible. Whether or not this happened to Ryan Shay is unknown, although perhaps in the coming days it will be revealed. The important point for everyone to learn is that when you feel that you have a viral infection, it's better to err on the side of caution and avoid competition. Also, as illustrated by the HCM and Coronary Artery abnormality cases, the presence of symptoms should be taken very, very seriously.
These are two of the most common conditions that cause SCD in young athletes, as well as a third possibility which is often in play in the elite athlete. There are of course many others, including mitral valve prolapse, a condition diagnosed in Chad Schieber, who died in the Chicago Marathon.
Over the coming days, the autopsy results and further insights may be revealed. If that is the case, then we'll do our very best to interpret and explain them. Until then, we mourn the death of a young athlete and look with new perspective on upcoming sports events.
Read more on sudden cardiac death, heart attacks and marathon medicine at these posts.
- Heart attack in Alberto Salazar - Coronary Artery disease?
- Sudden cardiac death in sport - a call to action from FIFA and soccer
- Chad Schieber death in the 2007 Chicago Marathon - Autopsy results and discussion
- Chicago Marathon death - no evidence of dehydration