Cardiology is a branch of medicine that deals with the disorders of the heart as well as some parts of the circulatory system. The field includes medical diagnosis and treatment of congenital heart defects, coronary artery disease, heart failure, valvular heart disease and electrophysiology. Physicians who specialize in this field of medicine are called cardiologists, a specialty of internal medicine. Pediatric cardiologists are pediatricians who specialize in cardiology.
Although the cardiovascular system is inextricably linked to blood, cardiology is relatively unconcerned with hematology and its diseases. Some obvious exceptions that affect the function of the heart would be blood tests, decreased oxygen carrying capacity, and coagulopathies.