In St Vincent's Hospital, he worked with surgeon Harry Windsor (who had performed Australia's first heart transplant in 1968) and Mark Shanahan. The advent of anti-rejection drugs in 1980 made heart transplants more feasible, and Chang lobbied politicians and businessmen to raise funds to establish a heart transplant program at St. Vincent's. On 8 April 1984, a team of doctors led by Chang operated on 14-year-old Fiona Coote who became Australia's youngest heart transplant patient.
Concerned about a shortage of organ donors, he arranged financing and assembled a team of scientists, engineers along with a marketing specialist to develop an artificial heart and manufacture inexpensive heart valves. Frank Tamru, the heart valve marketing and sales specialist met Dr. Chang in 1980 while working for Shiley the leading US company and based in Singapore. Along with engineers Richard Martin and Brij Gupta the group headquartered in Singapore set up facilities in Guangzhou and Sydney to developed mechanical and tissue heart valves called the St. Vincent's Heart Valves, which were widely implanted throughout Asia. The company, Pacific Biomedical Enterprises Ltd was the first in Asia to produce heart valves for Asian patients made by Asian workers. Chang and his team also made significant progress on the design of an artificial heart. His research projects ended with his death.