Cardiology is a branch of internal medicine that deals with the diagnosis and treatment of various heart disorders, such as coronary artery disease, congenital heart defects, valvular heart disease, and heart failure. Subspecialties include cardiac electrophysiology, echocardiography, nuclear cardiology, and interventional cardiology. Since the 1980's, cardiology has mushroomed into a specialty, and a lot has been achieved in all the subspecialty areas. According to the WHO, cardiovascular diseases are the dominant cause of death globally (31% of all global deaths). It further estimates that by 2030, nearly 23.6 million people will die due to cardiovascular diseases, especially stroke and heart disease. The high prevalence of various heart diseases would remain a challenge for the next 30 years.