What does it mean to be a carrier?

There are certain people who are gene carriers for some of the conditions such as hypertrophic cardiomyopathy or long QT syndrome but these individuals do not manifest any of the clinical features, ECG features or echocardiographic features of the condition. These types of individuals are known as obligate carriers. They can, however, pass the gene on to their children who may have the full blown version of the condition that they have passed on. When it comes to exercise, expert opinions vary, our own opinion is that if someone is a gene carrier but does not show any features of the condition on clinical testing, we do not prevent them from exercise and that seems to be the stance that the Americans have taken as well.