What is the remedy for bypass surgery patients who is suffering from itches on stitches and kind of contraction of stitches?

Stitches will contract they are designed to shrink some to ensure they heal the skin together and don't stretch letting the cut to reopen and itching typically is a sign of healing (Do to skin reconstruct and death.) You are looking for yellow coloration around the cut that is infection and red stripes leading away from the wound usually leading toward the heart that is also a sign of infection otherwise your fine.

There are not many stitches to be removed with this kind of surgery. Expect to have them removed shortly. Tell your doctor by phone.