Is there a treatment for athlete's heart?

Athlete's heart. Is a normal variant caused by the excellent conditioning, it isn't really an abnormality.
It doesn't need any. If by athlete's heart you mean athletic bradycardia or a slow heart rate with enlargement of the size of the heart muscle due to regular sustained cardiovascular exercise, then no treatment is necessary. In contrast, the pathologic condition of hypertrophic cardiomyopathy which can cause sudden death in young athletes is a very serious condition that requires early diagnosis and care.