Art De Vany has been saying this for some time now. Endurance sports may harm the heart:
Ventricular arrhythmia (VA), a disturbance that occurs in the ventricles or lower chambers of the heart, is a condition that can cause sudden death in top athletes who have had no previous symptoms of the disorder.After studying Dutch and Belgian endurance athletes with VA and other healthy sportspeople and volunteers, the researchers found that in the athletes with the problem the right ventricle (RV) of the heart was not functioning normally.
They believe VA, which could have many underlying causes, may be triggered by intense exercise or that endurance sports could promote the arrhythmia along with genetic or environmental factors.