Cardiac question re: ability to repair itself

Patient: My son, age 31 is an elite athlete- sponsored by The Northface for ultratrail marathons (50-100 miles each) He just had his first EKG and learned that he has an enlarged left ventricle- which I understand is normal for an extreme athlete. My question is: Once he stops his extreme athleticism, will his heart repair itself and become normal in size or is the damage not repairable?

Symptoms: Fatigue with exertion