Coronary artery bypass grafting or "CABG" (often pronounced "cabbage") is the most commonly performed "open heart" operation in the United States. Cardiothoracic surgeons perform the procedure to bypass blockages or obstructions of the coronary arteries.

Mitral Valve Replacement is the removal of the native valve that sits between the left atrium and the left ventricle and its replacement with a new valve either mechanical or tissue.

Mitral Valve Repair avoids removal of this valve repairing it instead. Not all valves can be repaired and the procedure can be complicated and lengthy but postoperative care is simpler.

Aortic Valve Replacement is the removal of the valve that sits between the left ventricle and the aorta which carries oxygenated blood to the body.

Thoracic/Lung Surgery involves many different procedures for multiple problems. The STS link gives mostly info on Cancer Diagnosis and Surgery but covers many procedures performed by Thoracic Surgeons.