By-pass surgery is a technique of treating patients with blocked coronary arteries which impair functioning of the heart. Coronary arteries are the blood vessels that supply blood to the heart muscles. They can narrow gradually and may even become completely blocked due to deposition of fatty substances. When this happens, blood supply to a particular part of the heart is reduced or cut off and the patient suffers from severe chest pain or may even collapse. An alternate path for blood-supply by-passing the blocked artery is then provided by attaching a piece of vein taken from the patient’s own leg.
During the by-pass surgery, the patient’s heart is emptied of blood by inserting two tubes, one into the aorta and the other into the vena cava. These two tubes are connected to a heart-lung machine which takes over the pumping and oxygenation of blood during the surgery. The patient’s heart once empty stops spontaneously or can be stopped by giving special drugs or by an electric shock for the surgery to be carried out.