Cardiology is a subspecialty of internal medicine. A doctor of cardiology—a cardiologist—deals with diseases and maladies of the heart and blood vessels (the cardiovascular system). Cardiologists are experts in the processes and prevention of heart disease, as well as in ways to improve survival rates and the quality of life for people who have suffered from such cardiovascular problems as heart attacks or coronary artery disease. Cardiologists do a three-year residency in internal medicine before completing a three-year residency in cardiology. Minimum postgraduate training: six years.