How is a coronary artery bypass surgery (cabg) done?

Complex, routine. With or without a heart-lung machine to isolate the heart from the circulation, conduits like vein segments or arteries are placed from the aorta (oxygenated blood) to the target artery beyond the blockage site, thus restoring oxygen to the heart muscle. If suitable, off-pump procedures can be used, though uncertain how much is gained with that less traumatic technique.
Carefully. Bypass surgery involves connecting a new tube (artery or vein) to a coronary artery past a blockage. It is done on a stopped heart using the heart lung machine or on a beating heart by stabilizing the heart with certain devices.