What happens if scar forms on the heart after aortic valve replacement surgery, is there any remedy for this?

No need: Scarring occurs as a healing process. There is no need to do anything unless the scar constricts your heart called constrictive pericarditis. Symptoms are shortness of breath, leg swelling, tiredness etc.

Scar on heart : Constrictive pericarditis or scarring after aortic valve replacement is a rate complication. If symptoms are noted to be from scarring, surgery can be offered. An echocardiogram may be required for the diagnosis.