 Yu performed pioneering research in cardiac physiology, making seminal observations about the pulmonary circulation in health and disease, and the relationship to ventricular function, and key observations about the care of patients with coronary artery disease.He cared for prominent individuals such as the Taiwanese president Chiang Kai-shek and his family.He served in numerous leadership roles during his career, including a term as President of the American Heart Association (1972-3).