A thoracic surgeon is a doctor who performs surgical procedures on the chest such as the heart, lungs, or esophagus.
Source: Genetic and Rare Diseases (GARD) Information Center
The Society of Thoracic Surgeons: What is Cardiothoracic Surgeon?
American Board of Thoracic Surgery: Surgeon Search
Cardiothoracic Surgeons: What We Do and How We Care for You
American Medical Association: Doctor Finder