Cardiac Arrest During Long-Distance Running Races: A New Report

This past week, the results from an important study on the heart risks of long-distance running was reported in the New England Journal of Medicine.
A group of investigators from Boston looked at the experience of ~11 million runners who took part in half marathon or full marathon races in the United States between 2000 and 2010. This is the largest study of its kind ever undertaken.
The important findings were:
-59 athletes had cardiac arrest and 42 of those died
-For marathon runners the risk of cardiac arrest was 1.01 per 100,000 participants
-For half marathon runners the risk of cardiac arrest was 0.27 per 100,000 participants
-The risk for men was several-fold greater than for women
-The majority of deaths occurred during the last 6 miles of the marathon or the last 3 miles of the half marathon
-From medical records, the cause of cardiac arrest could be determined for 31 victims (23 of whom died). In most of the cases where the athlete died, there was a specific heart condition that was responsible:
---Hypertrophic cardiomyopathy (HOCM) in 8
---Possible HOCM in 7
---Hyperthermia in 1
---Arrhythmogenic right ventricular cardiomyopathy in 1
---Hyponatremia in 2
---No specific cause in 4
Some important, NEW observations were:
--The frequency of cardiac arrest is extremely low....and even lower than previously thought.
--The survival rate from cardiac arrest was surprisingly good, at 29%. This is much higher than previous reports for out-of-hospital cardiac arrest. It suggests that bystander CPR and early defibrillation may be readily available at race venues.
--The risk is greater in marathons, compared to half marathons. The reason(s) are not yet clear.
This new report provides the most comprehensive information yet on cardiac arrest during running races. Athletes should be encouraged by the extremely low rate of cardiac arrest and with the favorable survival rates reported. Athletes should also take note that the cause of cardiac arrest was most often due to an underlying cardiac condition that might be discoverable BEFORE participating in a traning program or race. It's reasonable to conclude that a pre-participation visit to the doctor for a careful physical examination and, potentially, cardiac testing might reduce an athlete's chances of being a victim.