Marathon Lessons

Ask the DOC

Anyone who runs marathons should know the history of the event. In 490 B.C., Pheidippides ran across the Plains of Marathon to Athens to announce the defeat of the Persian army. Once he arrived at the Atheneum, he informed the crowd about the great victory, then he collapsed and died. To quote Robert Browning: “Unforseeing one! Yes, he fought on Marathon day: so, when Persia was dust, all cried, ‘To Acropolis! Run, Pheidippides, one race more.’ Till in Athens, he broke: 'Rejoice, we conquer!' Joy in his blood bursting his heart, he died—the bliss!” Recent medical advances may have finally found an answer to why he died. Since 2000, the frequency of sudden death due to cardiac arrest has been rising in middle-aged men who run marathons and triathlons.

It is an indisputable fact that regular exercise has a cardioprotective effect, however vigorous exercise may trigger sudden cardiac death. In Japan, cardiac resuscitation personnel are stationed along marathon routes to resuscitate fallen runners, thereby reducing the number of sudden deaths. It is thought that men, especially middle-aged marathon runners and triathletes, may have undetected, or subclinical, coronary artery disease. Considering the fact that the first medication given to those suffering from a heart attack is aspirin, it is now a recommendation that some middle-aged male runners take a single pre-race dose of aspirin. In addition, it is being increasingly recommended that middle-aged males who run these races undergo a cardiac CT scan to assess their coronary artery calcium score. High coronary artery calcium scores (>100) have been linked to significant risk of sudden death during these races.

The explanation for increased coronary artery disease and calcium scores in experienced endurance athletes is that inflammation seen with repeated bouts of extreme exercise is caused by repeated episodes of rhabdomyolysis, which is the breakdown of muscle tissue. Muscle soreness after exercise is common, but muscle damage after extreme exercise is also common. This severe muscle damage releases toxins like myoglobin, a muscle protein, into the bloodstream, which causes inflammation and damages the inner lining of blood vessels, known as the endothelium. Repeated episodes of rhabdomyolysis and endothelial damage are thought to cause narrowing, thickening, plaque formation, and calcification of blood vessels. Smaller blood vessels, like coronary arteries, are more susceptible than larger ones. During vigorous exercise, these plaques may rupture, causing sudden occlusion of the vessel and sudden death.

A study was done on runners in the Boston Marathon. Male runners who had no symptoms other than muscle soreness had positive biomarkers in their blood similar to those undergoing acute coronary events. These markers included high cardiac troponins, high C-reactive proteins, and high levels of other markers like B-natriuretic peptide. They also had cardiac dysfunction seen on echocardiography. By using the calcium score, middle-aged endurance runners may assess their risk and need to use pre-race aspirin. So, if you are a male between 32 to 46 and an extreme athlete, get your doctor to order a cardiac CT scan (if your insurance will approve it, that is) and discuss your risk and need to use aspirin with your doctor. If only Hippocrates, who knew of and used aspirin, had been present at the Atheneum, Pheidippides might have been saved.

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