The objective of this chapter is to introduce the cardiovascular system. The cardiovascular system can be thought of as the transport system of the body. This system has three main components: the heart, the blood vessel and the blood itself. This chapter covers the review of the heart and circulation, cyanotic heart diseases, acyanotic heart diseases, obstructive heart diseases, nursing care of the family and child with congenital cardiac diseases, acquired heart diseases, arrhythmias, hypertension, Kawasaki disease, and shock. The heart is an amazing muscle that moves blood to and from the heart and lungs, and throughout the body, with the help of four valves (the tricuspid, pulmonary, mitral, and aortic) that open and close with each beat of the heart, controlling the direction of blood flow. Shock is a life-threatening medical condition as a result of insufficient blood flow throughout the body. Shock often accompanies severe injury or illness. Medical shock is a medical emergency.