Dr. Koullias has pursued a diverse career in cardiovascular surgery that includes his residency in general surgery at New York Medical College followed by his residency in cardiothoracic surgery at Yale University. On graduating from Yale, he returned to Greece to practice adult cardiac surgery from 2003 to 2007 in Athens. He maintained his affiliation as an active researcher at the Yale Aortic Center during this period. His interest in minimally invasive procedures led him to a four-month fellowship in advanced thoracic aortic endovascular surgery at the German Heart Institute in Berlin, where he gained experience also in the management of aortic complications in patients with Marfan disease. Subsequently, he returned to the United States to join a group practice in cardiac surgery in Peoria, Illinois, where he was an attending physician from 2007 to 2010 and had a faculty appointment at the University of Illinois. During this period, he gained further training in vascular and endovascular surgery at the Arizona Heart Institute, completing a six-month fellowship there. In 2013, Dr. Koullias completed his two-year fellowship training in vascular and endovascular surgery at Stony Brook in New York. An active scholar as well as clinician, he has numerous publications to his credit, including a book he co-wrote (The Role of the Endothelium in Coronary Artery Disease, 1997), numerous peer-reviewed articles, and several book chapters.