Sudden Death in Endurance Sports

Posted on Posted in blog, science

sudden: adj. sud·den \ˈsə-dən\ || happening or coming unexpectedly
death: needs no explanation

I recently participated in the Ironman Sports Medicine Conference in Kailua-Kona, HI. In this mini series I want to share some of the most interesting presentations and highlight as they relate to you.

The first talk that I think is worth mentioning was given by Aaron L. Baggish MD (Director, Cardiovascular Performance Program, Massachusetts General Hospital , Boston, MA). Aaron talked about sudden death in endurance sports.

I often found myself in a conversation where people (mostly from the other / non-athletic side of my life) say that marathon running is bad and I will die on course. OK, facts is, that happens. Actually cardiac arrest and sudden death rates during long-distance running races are ~ 1 per 184,000 and 1 per 259,000 participants, respectively. And that is looking at > 10 million runners (Kim et al, NEJM 2012). Odds are against you if you run a marathon over a half marathon and if you are male. On the bright side 29% of runners survived the event, likely due to the excellent medical coverage at these events (your odds on the street are only ~8%!). In fact, the BAA now regularly trains participants on a voluntary basis to become experienced in hands only CPR. I congratulate them on this effort!
Interestingly the large majority of these heart problems arise in the last quarter of the marathon. In a nutshell: Don’t try to sprint for that PR. Your body is really good at coping with a pre-existing condition when it can maintain an equilibrium, but things get out of whack when you increase the demand to rapidly (this is a serious comment).

On the flip side, when scientists interviewed the wives of 133 men without known prior heart disease who had had primary cardiac arrest and compared them to a control group, they found the following. Men with low levels of habitual activity (doctor talk for couch potato), the relative risk of cardiac arrest during exercise compared with that at other times (= couch) was a whopping 56%. Contrary, the risk for athletes at the highest level of habitual activity was only increased by 5%. Importantly, among the athletes, the overall risk of cardiac arrest — i.e., during and not during vigorous activity — was only 40% that of the sedentary men. The authors concluded that “Although the risk of primary cardiac arrest is transiently increased during vigorous exercise, habitual vigorous exercise is associated with an overall decreased risk of primary cardiac arrest.” A normal person would say “running’s my best bet to avoid a heart attack but if one strikes me, likely it’s gonna happen when I’m running”.

OK, so now why is this? In fact this is hard to answer as we cannot design a study to address this, and we must rely on after-the-fact analysis and estimate and approximate certain factors. A pretty good explanation for these events in young athletes is what’s called hypertrophic (increased in size) heart muscle disease and what’s known as sudden unexpected death syndrome (that’s a clever way of masking that we don’t know). In the older athlete, ~35 years and up, the incidence of an underlying atherosclerotic disease becomes much more likely. There are pros and cons to screening athletes for these diseases prior to the engagement in endurance sports. Chiefly the rate of false positives, i.e. that is people without disease being told they can’t exercise, is too high. Efforts are on the way to refine these criteria. I would encourage everyone to see their primary care before starting an endurance ‘adventure’, but not to be discouraged if the outcome is negative. In which case a more focused follow-up may be warranted and allow the athlete to engage in this wonderful sport.

To summarize. Don’t be discouraged, running and endurance exercise is good for you (here related to heart disease), if you have an underlying cardiac problem, yes, the running will more likely expose it, but you are much more likely to survive that event. I had to cut a lot of details for this summary, feel free to talk to me more about this next time you see me.

Who’s ready for the TCS NYC Marathon?!



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