American Heart Association Apr 23 2026 Physical activity in children and teenagers with cardiomyopathy (conditions that affect the heart muscle's structure and function, impairing its ability to pump or fill effectively), as well as children with implantable cardioverter-defibrillators (ICDs) may be safer than previous research suggested, according to a new scientific statement from the American Heart Association, published today in the Association's flagship peer-reviewed journal  Circulation .