My cardiologist says the heart can't be conditioned or de-conditioned is this true? the heart is a muscle, can't it get stronger?

Conditioned: There are numerous studies using imaging techniques on athletes. These show definite cardiac adaptation; the exact nature varies depending upon the nature of the sport. These changes are most easily demonstrated in elite athletes who train extensively. It might be more appropriate to think of the heart as becoming more efficient rather than stronger. There are definite structural changes too.