Enlarged left ventricle?

doesnt sound like your gp has done a very good job of putting your mind at ease over this. If this were a critical problem you would have been sent straight to hospital - so if you arent in hospital thats a good sign. Many people have left ventricular hypertrophy (enlarged left ventricle). In someone so young it would be normal to see familial history for there to be a heart problem. (congenital history) its more likely that you have another problem (mechanical or muscoloskeletal) especially if you havent been whizzed off for tests