I have a family member who will be undergoing cardiac bypass surgery soon. how is the leg vessel "fixed" after a portion is removed for the surgery?

Collaterals: Often if multiple bypasses are needed, veins are harvested from the leg for use. Post operatively part of rehab is walking and may require compression hose to prevent swelling in the leg till the body replaces the removed vein with new small veins that will take over the job of returning blood to the central circulation. Walking and exercise will encourage the growth that may take multiple months.