The heart is the muscular pump that pushes blood through the circulatory system. Each heartbeat can be felt as an arterial pulse. The heart valves when closed prevent the blood from leaking back into the heart. Understanding the cardiac cycle in reference to the opening and closing of the heart valves and genesis of the heart sounds is central to appreciating changes in valvular heart disease. The cardiac output is the volume of blood pumped out of the heart during each beat and is expressed as litres/minute. The pressure in the arteries, arterioles and veins is maintained by the vascular tone. This tone is adjusted through autonomic impulses from the vasomotor centre in the medulla. The centre is influenced by afferent impulses from many areas like the carotid body, aortic arch and chemoreceptors