surgery involving some type of repair directly to the exposed heart or coronary arteries, etc., during which the blood is diverted and circulated and oxygenated by mechanical means
See open-heart surgery in American Heritage Dictionary 4
(ōˈpən-härtˈ)
noun
Surgery in which the thoracic cavity is opened to expose the heart and the blood is recirculated and oxygenated by a heart-lung machine.