A cardiologist is a specialist with special training and skill in finding, treating and preventing diseases of the heart and blood vessels. A cardiologist is a heart doctor. He or she is the one to visit if you feel tightness in your chest and shortness of breath. Besides treating the heart, a cardiologist is also concerned with the circulatory system, including arteries and veins. The field includes medical diagnosis and treatment of congenital heart defects, coronary artery disease, heart failure, valvular heart disease and electrophysiology. Two types of specialization in cardiology are adult cardiology and pediatric cardiology.