With the heart-lung machine, which allows the heart to be transiently bypassed while the surgeon works on the heart, open-heart surgery has become practical and has allowed the correction or replacement of defective or diseased heart valves.

Anatomy

• The heart is a muscular organ about the size of a clenched fist. It lies in the chest beneath the sternum or breast bone
• The function of the heart is to supply blood to the body. The heart is divided into four chambers, two upper chambers called the right and left atria and two lower chambers called the right and left ventricles (Figure 1)

Figure 1- Anatomy of the heart and heart valves. The black arrows indicate the direction of blood flow through each valve. © N. Gordon