MODEL RELEASED. Heart bypass surgery. Operating theatre during a coronary artery bypass operation. A perfusionist is seen at lower right, monitoring a heart-lung machine. This machine takes over the function of the heart and lungs, allowing the heart to be stopped during the operation. Drugs for maintaining general anaesthesia are given to the patient through the tubes by his head (centre left). During a heart bypass operation, a vein taken from the leg is attached to the heart to re- route blood around a blockage in the coronary arteries (which supply the heart with blood). Blocked coronary arteries can cause a heart attack.