What happens in heart bypass surgery?

See below. A vein can be taken from the leg, sewn to the aorta and the other end is sewn to the coronary artery beyond a blockage. Thus blood flows from the aorta, through that vein, and then into the coronary artery bypassing the blockage. Alternatively, the internal mammary artery can be connected to the coronary artery.
Sternum commonly. In most the skin, soft tissue, sternum, pericardium are divided!. This shows the heart so the coronary arteries can be seen and bypassed. Valves may also be repaired or replaced.