Could you explain what is a bypass surgery that is done to the heart?

Bypass surgery. ... Uses blood vessels from your body, like veins from your leg or arteries from your chest or arms, to route blood around blockages in the arteries that distribute blood to your heart (so the blockage is "bypassed"). Your doctor can go into more detail.
Bypass. Coronary artery bypass surgery is done when there is significant narrowing or obstruction in the coronary arteries that feed the heart muscle. Bypass is done by connecting the part of the coronary artery(s) after the blockage to the aorta or artery using a vein graft or artery and thereby creating a detour, supplying blood flow to the affected area of the heart.