The Full form of CTVS is Cardiothoracic and Vascular Surgery. CTVS (also known as Thoracic Surgery) is the field of medicine involved in surgical treatment of organs inside the thorax (the chest), generally treatment of conditions of the heart (heart disease) and lungs (lung disease). In most countries, cardiac surgery (involving the heart and the great vessels) and general thoracic surgery (involving the lungs, thymus, esophagus, etc.) are separate surgical specialties; the exceptions are the Australia, United States, New Zealand, and some EU countries, such as the Portugal and United Kingdom. A cardiac surgery residency typically comprises anywhere from four to six years (or longer) of training to become a fully qualified surgeon. Cardiac surgery training may be combined with vascular surgery and / or thoracic surgery and called Cardiovascular (CV) / Cardiothoracic (CT) / Cardiovascular Thoracic (CVT) Surgery. Cardiac surgeons may enter a cardiac surgery residency directly from medical school, or first complete a general surgery residency followed by a fellowship. Cardiac surgeons may further sub-specialize cardiac surgery by doing a fellowship in a variety of topics including: pediatric cardiac surgery, adult acquired heart disease, cardiac transplantation, weak heart issues, and many more problems in the heart.