Pelliccia says that in most cases these abnormalities are due to the athletes' intensive training, which causes the heart to increase in size, especially among those taking part in endurance events such as cycling and running. Using ultrasound scans to produce an image of the heart, he was able to show that the vast majority of athletes with abnormal ECGs had no problems. But 5 per cent had heart defects, mainly in their heart valves, that would not have been spotted from the ECG alone, he reports in a forthcoming issue of Circulation . Pelliccia believes that these valve defects, which are linked to the left ventricle, may result from the athletes' intensive training. An enlarged heart is sometimes a sign of an inherited disease, congenital hypertrophic cardiomyopathy, which affects 1 in 1000 people and causes illness or death in young adults.
Young athletes are no less prone to the disease than anyone else.