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Sudden cardiac arrest a rare but real life threatening concern for runners and triathletes

Posted Apr 14 2011 10:00am

SCA Although sudden cardiac arrest (SCA) or sudden cardiac death is not common amongst marathon and half marathon runners, a recent cluster in such deaths has attracted considerable media attention and evoked concern over the safety of long distance running and the health benefits associated with it.

Perhaps the most high profile marathon death in recent years was that of top American runner Ryan Shay   who collapsed and died in November 2007 while competing in the US Olympic Trials marathon in Central Park.

His death was particularly shocking as he was an elite runner and marathon veteran, not a first timer or someone who hadn’t trained enough, leaving many people thinking if it could happen to him it could happen to anyone. (Subsequent tests showed Shay died of a heart attack due to a pre existing enlarged heart.

SCA in marathons are exceedingly rare events (three runners died within 20 minutes of each other in Detroit in 2009, last year one at Virginia Beach, one at Dallas).

Although there is no national reporting system for marathon deaths in the US, a recent study published in the British Medical Journal looked at 1,411,482 runners who participated from 1976-2010.

There were 31 SCAs....including 11 deaths.

The prevalence of SCA was 1 in 45,531 runners while 1 in 128,316 runners died. Thirty out of thirty one runners with SCA were male with an average age of 46.7. Six runners collapsed at the finish line, 6 in the final 2 miles, 6 from miles 17-23, and 10 before mile 16.

Autopsy diagnosis showed that 8 out of the 9 had coronary artery disease, and the other died of congenital heart disease complications. Two causes of death were unknown.

The conclusions from this were:

  • Sudden Cardiac Arrest associated with marathon running is exceedingly rare, is more common in middle to late age males and can occur anywhere along the course with the majority of cases in the final 10 miles.
  • Although heart disease is the most common cause of death in runners during marathons, other potentially life threatening conditions come in the form of hyponatremia and heat related illnesses.
  • Hyponatremia occurs when sodium is lost in the sweat that the body produces to cool itself whilst running. As salt levels drop in the blood, it does not do so in the cells. The body attempts to force salts out of the cells by flooding them causing swelling. Whilst muscles can expand the brain and this can be fatal.
  • In hot weather the body becomes dehydrated and the human thermoregulatory system is challenged and greater skin blood flow is required for cooling. This leads to a rise in core temperature which in turn can lead to heat exhaustion, heat stroke, coma and then death.
  • Comparatively marathon running is no more dangerous than other sports, has been shown to be safer than Triathlon and the association of endurance running with improved quality of life and longevity underscores the importance of putting these risks into perspective.

This story was written by Danny Ward our British Bureau Chief.

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