Why Do Healthy People Die Running Marathons?

Why Do Healthy People Die Running Marathons?

You’ve likely read the sad news from this weekend in the world of distance running: Three relatively young men died on Sunday while running in otherwise festive, long-distance races in London and Raleigh, North Carolina.

At the 34th London Marathon, where 36,000 runners participated on Sunday, the post-race death of a 42-year-old man was the event’s second death in three years. In North Carolina, two men died, age 31 and 35, after collapsing at or near the end of the 13.1-mile, half-marathon of the capital city’s inaugural Rock ‘N’ Roll Marathon. A combined 12,500 runners participated in the Raleigh events.

While specific details beyond the runners’ age and gender are not yet available, general reports on the three cases bear the hallmarks of sudden cardiac death. Each person collapsed late or at the end of the races and on-site resuscitation attempts were as prompt and aggressive as possible. But all three gentlemen were pronounced dead at the hospitals where they were taken.

Sudden death while running long distance races is rare phenomenon but is appearing to be more common due to the sheer number of runners participating across a racing calendar that continues to expand (the Raleigh race was the inaugural event there.).

While research shows that air temperature and race preparation are most likely to predict the best marathon finish times, sudden cardiac death is most often due to existing cardiovascular disease that is largely unrelated to the extent of physical conditioning. In many of these cases, the victims never had any previous problems or symptoms.

Rare events in large populations

Sudden deaths in marathon running have been the subject of much study in the cardiology and sports medicine fields because they are rare and somewhat unpredictable occurrences. Research estimates range from 0.5 to 2 deaths per 100,000 marathon runners in a given race, a far lower risk of death than in the majority of daily activities.

Dr. Dan Tunstall Pedoe, the London Marathon’s Medical Director from 1981 to 2006, wrote in the journal, Sports Medicine, that an increase in marathon popularity as one contributor to the apparent increase in long-distance racing deaths.

Dr. Pedoe examined the records of documented sudden deaths across 650,000 marathon completions during that time, concluding that such risk in the London Marathon was 1 in 80,000 finishers. That’s not far removed from London’s two deaths in the last three years across about 105,000 runners (although the 2012 death of 30-year-old Claire Squiers has been primarily attributed to her use of a sports supplement containing the amphetamine-like drug, DMAA.).

A silent, genetic cause

These rare, tragic events deal a crushing blow to family members and the larger community, in part because even recreational marathoners are widely considered to be at their peak of physical conditioning.

But is there any way that sudden cardiac deaths in people under 40 or so could be prevented by detecting heart problems in advance? In older individuals, atherosclerosis or coronary artery disease is most often the cause of sudden death during athletic events but these situations will sometimes cause symptoms during training.

“When someone suddenly dies in an athletic event, particularly in teenagers and those in their 20s and 30s – the most common cause is hypertrophic obstructive cardiomyopathy,” says Peter A. McCullough, M.D., M.P.H., a cardiologist at the Baylor University Medical Center at Dallas.

“This is a genetic abnormality of the proteins used by heart muscle cells. The heart becomes abnormally thick in one area and when the heart pumps, it has trouble ejecting blood past that thick point. The heart becomes very, very thick – two to three times as thick as normal,” said Dr. Mc Cullough.

This heart disorder, abbreviated HOCM or HCM, only starts to express itself around the time of puberty in boys and girls, so it can’t be detected at birth.

You may already be familiar with the term, “athlete’s heart,” an adaptation where people who exercise frequently often develop a mild, generalized, and even-proportioned enlargement of the heart. But, HOCM is a distinctly different and pathological phenomenon. Here, the area of the heart where the unbalanced thickening (hypertrophy) occurs is in the walls of one chamber of the heart, the left ventricle, and particularly in the partition that separates the two ventricular chambers.

In addition, cardiac muscle cells and the fibers within them that are responsible for coordinated contraction and relaxation of heart muscle appear microscopically to be quite disorderly, an arrangement appropriately called myofibril disarray. The faulty and inefficient organization of these fibers is most often due to mutations in one of the nine types of proteins that make up these fibers.

“This can be the setup for an abnormal, circular heart rhythm that can take off on its own, called a re-entrant arrhythmia, that can degenerate into full-blown cardiac arrest,” says Dr. McCullough. “The reason why it happens with exertion, and, in particular with dehydration, is that there’s a decrease in the blood volume.”

With the ventricles already having trouble filling with blood and ejecting it out, the abnormal heart rhythm develops, potentially because of less oxygen delivery to the heart muscle.

As to why some deaths seem to occur at the end of the race, McCullough says, ”There’s still a lot of circulating adrenaline so the heart is pumping very, very hard, but there’s relatively little blood to fill it.”

Moreover, blood pools in the legs when you stop running because there’s no longer the contraction of muscles that helps push the blood back up.

A 2012 study published in the New England Journal of Medicine by the multi-institutional research team, the Race Associated Cardiac Arrest Event Registry (RACER) Study Group, showed that nearly 80% of the non-survivors of cardiac arrest collapsed in the final 25% of the distance of marathons and half-marathons, or shortly after finishing.

The RACER study was exhaustive, examining 59 cardiac arrests among 10.9 million registrants for marathons and half-marathons between 2000 and 2010. One additional concern that arose from this study is that men had an increased rate of risk of cardiac events over the study period that averaged five times greater than that of women. The authors posited that distance racing might be attracting a greater proportion of men with unrecognized cardiac disease who seek the health benefits of exercise.

Most dramatically, the study showed that younger runners (under age 40) experiencing cardiac arrest were almost seven times less likely to survive than runners over 40 (7% vs. 47%). The reason, the authors stated, was that the underlying cardiac disease was distinctly different: In those cases under age 40, the predominant condition was hypertrophic cardiomyopathy whereas older runners had ischemic heart disease, a condition that’s more responsive to resuscitation efforts.

Another contributing factor to the low survival rate of those patients under 40 is that the ventricular tachycardia that precedes cardiac arrest – heart rates of 220-240 beats per minute – can only be reversed by a portable cardiac defibrillator during the first minute or two. Once the condition progresses to ventricular fibrillation, where the heart is essentially quivering and doing no actually pumping – oxygen deprivation has already progressed toward the point of no return.

So even if a defibrillator was at each water station – usually spaced every two miles – even a five-minute miler wouldn’t be able to get the apparatus to the victim in time.

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SOURCE: Forbes.com

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