Cardiac Surgery

The function of the heart is to keep oxygen-rich blood circulating through the body. The cells of the body need a steady supply of oxygen, particularly those in the brain. To serve this purpose, the heart acts as a pump, divided into four chambers which are connected by tiny flaps of tissue called valves.

The chambers of the heart work together to keep blood circulating. At the end of each cycle, veins return the blood to the right atrium, the first of the four chambers. The oxygen in this blood has been depleted and the blood must be delivered to the lungs, where carbon dioxide is exchanged for oxygen. From the right atrium, the blood flows through the tricuspid valve and into the second chamber, the right ventricle. The right ventricle contracts when it is filled, pushing the blood through the pulmonary artery which leads to the lungs.

From the lungs, the blood travels through the pulmonary veins to the third chamber, the left atrium. When the left atrium is filled, it forces the blood through the mitral valve to the left ventricle. From there, it is pushed into a major blood vessel, called the aorta, for distribution throughout the body.

The contractions of these four chambers are co-ordinated by electrical impulses from a tissue called the pacemaker, which is located in the right atrium. Normally, about 70 signals are sent out from the pacemaker each minute, making the heart's chambers contract in the proper sequence.

Since the heart is made of muscle, it must have its own blood supply, which is provided by the coronary arteries. Heart disease can result from damage to the heart muscle, the valves, the pacemaker or the coronary arteries. If the muscle is damaged, the heart is unable to pump properly. If the valves are damaged, blood cannot flow normally from one chamber to the next. If the coronary arteries are damaged, the heart muscle does not receive proper nourishment from the blood. If the conducting system, or some muscle area, is damaged, the pattern of muscle activation is altered. In severe cases this can lead to poor pump activity or death.